[PATCH v12 00/45] guest_memfd: In-place conversion support

[PATCH v12 00/45] guest_memfd: In-place conversion support

[Ackerley Tng via B4 Relay]

Here's v12. Thanks everyone for the comments and fast responses!  We're now
at ~4 weeks to soft-close at 7.3-rc5.

v12 is based on 7.3-rc1 (contains the mm/ bugfixes). Like v11, v12 is also
dependent on another series [3], which makes kvm_gmem_get_pfn() NOT return
a refcounted page to KVM.

Here's everything stitched together for your convenience:

https://github.com/googleprodkernel/linux-cc/commits/guest_memfd-inplace-conversion-v12

This revision resolves the issue on v10/v11 to do with over-zapping of
non-gmem memory because of the requested filters. [1]

The resolution is in a new patch "KVM: guest_memfd: Always fault from
guest_memfd if in-place conversion is enabled". I also updated the
documentation as requested.

Documentation updates are in these patches:

+ KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion
+ KVM: guest_memfd: Always fault from guest_memfd if in-place conversion is enabled
+ KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2

The documentation update in v10's "KVM: Let userspace disable per-VM mem
attributes, enable per-gmem attributes" was misplaced imo so I folded it
conceptually into the patches above.

private_mem_conversions_test was updated in v11 to test dual backing, and
that's meaningless now since with gmem_in_place_conversions, we're now
always faulting from guest_memfd, and the userspace_addr not being from the
gmem associated with the memslot is considered a user error.

I now only have 1 patch "KVM: selftests: Update
private_mem_conversions_test for in-place conversions" instead of 2 in v11.

Resolves discussion at [2].

Here's v12 with tests:

https://github.com/googleprodkernel/linux-cc/commits/guest_memfd-inplace-conversion-coco-selftests-v12

Tested with both CONFIG_KVM_VM_MEMORY_ATTRIBUTES enabled and disabled:

+ tools/testing/selftests/kvm/guest_memfd_test.c
+ tools/testing/selftests/kvm/pre_fault_memory_test.c
+ tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+ tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+ tools/testing/selftests/kvm/x86/private_mem_kvm_exits_test.c

[1] https://lore.kernel.org/all/apCLFSbj8sq2biJp@google.com/
[2] https://lore.kernel.org/all/apCj6gz8x24Dkle8@google.com/
[3] https://lore.kernel.org/all/20260826-gmem-no-return-page-v4-0-3bb9c1ddb4e3@google.com/

v11: https://patch.msgid.link/20260826-gmem-inplace-conversion-v11-0-0a15d8a799aa@google.com
v10: https://lore.kernel.org/r/20260807-gmem-inplace-conversion-v10-0-2fc18ee6d3ba@google.com
v9: https://lore.kernel.org/r/20260728-gmem-inplace-conversion-v9-0-35f9aec2aed2@google.com
v8: https://lore.kernel.org/r/20260618-gmem-inplace-conversion-v8-0-9d2959357853@google.com
v7: https://lore.kernel.org/r/20260522-gmem-inplace-conversion-v7-0-2f0fae496530@google.com
v6: https://lore.kernel.org/r/20260507-gmem-inplace-conversion-v6-0-91ab5a8b19a4@google.com
RFC v5: https://lore.kernel.org/r/20260428-gmem-inplace-conversion-v5-0-d8608ccfca22@google.com
RFC v4: https://lore.kernel.org/all/20260326-gmem-inplace-conversion-v4-0-e202fe950ffd@google.com/T/
RFC v3: https://lore.kernel.org/r/20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com/T/
RFC v2: https://lore.kernel.org/all/cover.1770071243.git.ackerleytng@google.com/T/
RFC v1: https://lore.kernel.org/all/cover.1760731772.git.ackerleytng@google.com/T/

Previous versions of this feature, part of other series, are available at:

+ https://lore.kernel.org/all/bd163de3118b626d1005aa88e71ef2fb72f0be0f.1726009989.git.ackerleytng@google.com/
+ https://lore.kernel.org/all/20250117163001.2326672-6-tabba@google.com/
+ https://lore.kernel.org/all/b784326e9ccae6a08388f1bf39db70a2204bdc51.1747264138.git.ackerleytng@google.com/

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
Ackerley Tng (23):
      KVM: Rename kvm_mem_is_private() to kvm_is_private_gfn()
      KVM: guest_memfd: Always fault from guest_memfd if in-place conversion is enabled
      KVM: guest_memfd: Pass mapping type filter to invalidation helper
      KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2
      KVM: guest_memfd: Ensure pages are not in use before conversion
      KVM: guest_memfd: Call arch make_shared callback for to-shared conversion
      KVM: guest_memfd: Return early if range already has requested attributes
      KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check
      KVM: guest_memfd: Zero page while getting pfn
      KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION
      KVM: selftests: Test basic single-page conversion flow
      KVM: selftests: Test conversion flow when INIT_SHARED
      KVM: selftests: Test conversion precision in guest_memfd
      KVM: selftests: Test conversion before allocation
      KVM: selftests: Convert with allocated folios in different layouts
      KVM: selftests: Test that truncation does not change shared/private status
      KVM: selftests: Add helpers to pin pages with CONFIG_GUP_TEST
      KVM: selftests: Test conversion with elevated page refcount
      KVM: selftests: Reset shared memory after hole-punching
      KVM: selftests: Provide function to look up guest_memfd details from gpa
      KVM: selftests: Make TEST_EXPECT_SIGBUS thread-safe
      KVM: selftests: Set up page size and alignment independently for guest_memfd
      KVM: selftests: Update private_mem_conversions_test for in-place conversions

Michael Roth (1):
      KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE

Sean Christopherson (21):
      KVM: guest_memfd: Optimize away conversion overheads via dead-code elimination
      KVM: guest_memfd: Use kvm_mem_is_private() when populating guest_memfd memory
      KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings
      KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES
      KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined
      KVM: Rename memory attribute APIs to prepare for in-place gmem conversion
      KVM: Provide generic interface for checking memory private/shared status
      KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion
      KVM: Consolidate private memory and guest_memfd ifdeffery in kvm_host.h
      KVM: guest_memfd: Invalidate both SHARED and PRIVATE mappings for in-place conversions
      KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86
      KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes
      KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs
      KVM: selftests: Create gmem fd before "regular" fd when adding memslot
      KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset}
      KVM: selftests: Add support for mmap() on guest_memfd in core library
      KVM: selftests: Add selftests global for guest memory attributes capability
      KVM: selftests: Add helpers for calling ioctls on guest_memfd
      KVM: selftests: Test that shared/private status is consistent across processes
      KVM: selftests: Provide common function to set memory attributes
      KVM: selftests: Update private memory exits test to work with per-gmem attributes

 Documentation/admin-guide/kernel-parameters.txt    |  25 +
 Documentation/virt/kvm/api.rst                     | 107 ++++-
 .../virt/kvm/x86/amd-memory-encryption.rst         |  14 +-
 Documentation/virt/kvm/x86/intel-tdx.rst           |   4 +
 arch/x86/include/asm/kvm-x86-ops.h                 |   2 +-
 arch/x86/include/asm/kvm_host.h                    |   9 +-
 arch/x86/kvm/Kconfig                               |  15 +-
 arch/x86/kvm/mmu/mmu.c                             |  28 +-
 arch/x86/kvm/svm/sev.c                             |  13 +-
 arch/x86/kvm/vmx/tdx.c                             |   8 +-
 arch/x86/kvm/x86.c                                 |  20 +-
 include/linux/kvm_host.h                           |  83 ++--
 include/trace/events/kvm.h                         |   6 +-
 include/uapi/linux/kvm.h                           |  16 +
 mm/folio.c                                         |   2 +
 tools/testing/selftests/kvm/Makefile.kvm           |   1 +
 tools/testing/selftests/kvm/include/kvm_util.h     | 139 +++++-
 tools/testing/selftests/kvm/include/test_util.h    |  34 +-
 tools/testing/selftests/kvm/lib/kvm_util.c         | 222 +++++----
 tools/testing/selftests/kvm/lib/test_util.c        |   7 -
 .../kvm/x86/guest_memfd_conversions_test.c         | 512 +++++++++++++++++++++
 .../kvm/x86/private_mem_conversions_test.c         |  66 ++-
 .../selftests/kvm/x86/private_mem_kvm_exits_test.c |  36 +-
 virt/kvm/Kconfig                                   |   3 -
 virt/kvm/guest_memfd.c                             | 469 +++++++++++++++++--
 virt/kvm/kvm_main.c                                |  92 ++--
 26 files changed, 1646 insertions(+), 287 deletions(-)
---
base-commit: a0c789941a3d705d00c018b3c9348b4b930c0c74
change-id: 20260225-gmem-inplace-conversion-bd0dbd39753a

Best regards,
--
Ackerley Tng <ackerleytng@google.com>

[PATCH v12 01/45] KVM: guest_memfd: Optimize away conversion overheads via dead-code elimination

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Add and use kvm_arch_has_gmem_convert() to guard guest_memfd's invocation
of arch hooks related to converting memory between private and shared, as
only one half of the x86 CoCo duo needs the runtime hooks (any pre-work is
pure overhead for TDX).  At this exact moment, the overhead is negligible,
but that will change when in-place conversion comes along, at which point
to-shared conversions will "need" to find all affected folios prior to
calling into arch code.  In quotes because very technically that work could
be pushed to arch code, but that would bleed guest_memfd details into arch
code and would be far worse than adding yet another kvm_arch_has... hook.

Opportunistically provide the kvm_arch_gmem_make_private() declaration, and
rely on dead-code elimination to eliminate the call to non-existent code
when CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT=n.

Reported-by: Binbin Wu <binbin.wu@linux.intel.com>
Closes: https://lore.kernel.org/all/1ec08cd8-3072-4753-ad5e-cd34956647f8@linux.intel.com
Suggested-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 arch/x86/include/asm/kvm_host.h | 3 +++
 include/linux/kvm_host.h        | 3 ++-
 virt/kvm/guest_memfd.c          | 5 ++---
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 683bb8bf43a94..6beddd8a0c749 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1854,6 +1854,9 @@ enum kvm_intr_type {
 #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
 #define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem)
 #endif
+#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
+#define kvm_arch_has_gmem_convert() (!!kvm_x86_ops.gmem_make_private)
+#endif
 
 #define kvm_arch_has_readonly_mem(kvm) (!(kvm)->arch.has_protected_state)
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 502465119ca0c..b7516e19ef419 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2597,9 +2597,10 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm,
 }
 #endif /* CONFIG_KVM_GUEST_MEMFD */
 
-#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
 int kvm_arch_gmem_make_private(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 			       kvm_pfn_t nr_pages);
+#ifndef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
+#define kvm_arch_has_gmem_convert() false
 #endif
 
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 798d91df69537..2190e4d6b6bea 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -772,11 +772,10 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
 		folio_mark_uptodate(folio);
 	}
 
-#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
-	if (kvm_gmem_is_private_mem(file_inode(file), index))
+	if (kvm_arch_has_gmem_convert() &&
+	    kvm_gmem_is_private_mem(file_inode(file), index))
 		r = kvm_arch_gmem_make_private(kvm, gfn, *pfn,
 					       (kvm_pfn_t)1 << *max_order);
-#endif
 
 	folio_unlock(folio);
 	folio_put(folio);

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 01/45] KVM: guest_memfd: Optimize away conversion overheads via dead-code elimination

[Fuad Tabba]

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Sean Christopherson <seanjc@google.com>
>
> Add and use kvm_arch_has_gmem_convert() to guard guest_memfd's invocation
> of arch hooks related to converting memory between private and shared, as
> only one half of the x86 CoCo duo needs the runtime hooks (any pre-work is
> pure overhead for TDX).  At this exact moment, the overhead is negligible,
> but that will change when in-place conversion comes along, at which point
> to-shared conversions will "need" to find all affected folios prior to
> calling into arch code.  In quotes because very technically that work could
> be pushed to arch code, but that would bleed guest_memfd details into arch
> code and would be far worse than adding yet another kvm_arch_has... hook.
>
> Opportunistically provide the kvm_arch_gmem_make_private() declaration, and
> rely on dead-code elimination to eliminate the call to non-existent code
> when CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT=n.
>
> Reported-by: Binbin Wu <binbin.wu@linux.intel.com>
> Closes: https://lore.kernel.org/all/1ec08cd8-3072-4753-ad5e-cd34956647f8@linux.intel.com
> Suggested-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

Cheers,
/fuad

> ---
>  arch/x86/include/asm/kvm_host.h | 3 +++
>  include/linux/kvm_host.h        | 3 ++-
>  virt/kvm/guest_memfd.c          | 5 ++---
>  3 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 683bb8bf43a94..6beddd8a0c749 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1854,6 +1854,9 @@ enum kvm_intr_type {
>  #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
>  #define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem)
>  #endif
> +#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
> +#define kvm_arch_has_gmem_convert() (!!kvm_x86_ops.gmem_make_private)
> +#endif
>
>  #define kvm_arch_has_readonly_mem(kvm) (!(kvm)->arch.has_protected_state)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 502465119ca0c..b7516e19ef419 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2597,9 +2597,10 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm,
>  }
>  #endif /* CONFIG_KVM_GUEST_MEMFD */
>
> -#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
>  int kvm_arch_gmem_make_private(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
>                                kvm_pfn_t nr_pages);
> +#ifndef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
> +#define kvm_arch_has_gmem_convert() false
>  #endif
>
>  #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 798d91df69537..2190e4d6b6bea 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -772,11 +772,10 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
>                 folio_mark_uptodate(folio);
>         }
>
> -#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
> -       if (kvm_gmem_is_private_mem(file_inode(file), index))
> +       if (kvm_arch_has_gmem_convert() &&
> +           kvm_gmem_is_private_mem(file_inode(file), index))
>                 r = kvm_arch_gmem_make_private(kvm, gfn, *pfn,
>                                                (kvm_pfn_t)1 << *max_order);
> -#endif
>
>         folio_unlock(folio);
>         folio_put(folio);
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

Re: [PATCH v12 01/45] KVM: guest_memfd: Optimize away conversion overheads via dead-code elimination

[Binbin Wu]

On 8/31/2026 8:25 AM, Ackerley Tng via B4 Relay wrote:
> From: Sean Christopherson <seanjc@google.com>
> 
> Add and use kvm_arch_has_gmem_convert() to guard guest_memfd's invocation
> of arch hooks related to converting memory between private and shared, as
> only one half of the x86 CoCo duo needs the runtime hooks (any pre-work is
> pure overhead for TDX).  At this exact moment, the overhead is negligible,
> but that will change when in-place conversion comes along, at which point
> to-shared conversions will "need" to find all affected folios prior to
> calling into arch code.  In quotes because very technically that work could
> be pushed to arch code, but that would bleed guest_memfd details into arch
> code and would be far worse than adding yet another kvm_arch_has... hook.
> 
> Opportunistically provide the kvm_arch_gmem_make_private() declaration, and
> rely on dead-code elimination to eliminate the call to non-existent code
> when CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT=n.
> 
> Reported-by: Binbin Wu <binbin.wu@linux.intel.com>
> Closes: https://lore.kernel.org/all/1ec08cd8-3072-4753-ad5e-cd34956647f8@linux.intel.com
> Suggested-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>

[PATCH v12 02/45] KVM: guest_memfd: Use kvm_mem_is_private() when populating guest_memfd memory

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Use kvm_mem_is_private() when populating guest_memfd instead of using an
open coded equivalent.  In addition to simplifying the populate code *now*,
this avoids the need to provide a range-based gmem lookup API in the future
as well.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Suggested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 virt/kvm/guest_memfd.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 2190e4d6b6bea..69612bf146be1 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -805,9 +805,7 @@ static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot,
 
 	folio_unlock(folio);
 
-	if (!kvm_range_has_memory_attributes(kvm, gfn, gfn + 1,
-					     KVM_MEMORY_ATTRIBUTE_PRIVATE,
-					     KVM_MEMORY_ATTRIBUTE_PRIVATE)) {
+	if (!kvm_mem_is_private(kvm, gfn)) {
 		ret = -EINVAL;
 		goto out_put_folio;
 	}

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 03/45] KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Start plumbing in guest_memfd support for in-place private<=>shared
conversions by tracking attributes via a maple tree.  KVM currently tracks
private vs. shared attributes on a per-VM basis, which made sense when a
guest_memfd _only_ supported private memory, but tracking per-VM simply
can't work for in-place conversions as the shared/private status of a given
page needs to be per-gmem_inode, not per-VM.

Use the filemap invalidation lock to protect the maple tree, as taking the
lock for read when faulting in memory (for userspace or the guest) isn't
expected to result in meaningful contention, and using a separate lock
would add significant complexity (avoiding deadlock is quite difficult).

In kvm_gmem_get_pfn(), drop the folio refcount before releasing
filemap_invalidate_lock(). This ensures that a competing conversion request
from userspace (to be added in a later patch), which also takes the
filemap_invalidate_lock(), will never see an elevated refcount due to
kvm_gmem_get_pfn().

Co-developed-by: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Co-developed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 virt/kvm/guest_memfd.c | 136 ++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 119 insertions(+), 17 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 69612bf146be1..e32ac2c28cbef 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -4,6 +4,7 @@
 #include <linux/falloc.h>
 #include <linux/fs.h>
 #include <linux/kvm_host.h>
+#include <linux/maple_tree.h>
 #include <linux/mempolicy.h>
 #include <linux/pseudo_fs.h>
 #include <linux/pagemap.h>
@@ -34,6 +35,13 @@ struct gmem_inode {
 	struct list_head gmem_file_list;
 
 	u64 flags;
+	/*
+	 * Every index in this inode, whether memory is populated or
+	 * not, is tracked in attributes. The entire range of indices,
+	 * corresponding to the size of this inode, is represented in
+	 * this maple tree.
+	 */
+	struct maple_tree attributes;
 };
 
 static __always_inline struct gmem_inode *GMEM_I(struct inode *inode)
@@ -61,9 +69,28 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn)
 	return gfn - slot->base_gfn + slot->gmem.pgoff;
 }
 
+static u64 kvm_gmem_get_default_attributes(struct inode *inode)
+{
+	bool init_shared = GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED;
+
+	return init_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
+}
+
+static u64 kvm_gmem_get_attributes(struct inode *inode, void *entry)
+{
+	if (WARN_ON_ONCE(!entry))
+		return kvm_gmem_get_default_attributes(inode);
+
+	return xa_to_value(entry);
+}
+
 static bool kvm_gmem_is_private_mem(struct inode *inode, pgoff_t index)
 {
-	return !(GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED);
+	struct maple_tree *mt = &GMEM_I(inode)->attributes;
+	void *entry = mtree_load(mt, index);
+
+	return kvm_gmem_get_attributes(inode, entry) &
+	       KVM_MEMORY_ATTRIBUTE_PRIVATE;
 }
 
 static bool kvm_gmem_is_shared_mem(struct inode *inode, pgoff_t index)
@@ -364,10 +391,13 @@ static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf)
 	if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
 		return VM_FAULT_SIGBUS;
 
-	if (!kvm_gmem_is_shared_mem(inode, vmf->pgoff))
-		return VM_FAULT_SIGBUS;
+	filemap_invalidate_lock_shared(inode->i_mapping);
+	if (kvm_gmem_is_shared_mem(inode, vmf->pgoff))
+		folio = kvm_gmem_get_folio(inode, vmf->pgoff);
+	else
+		folio = ERR_PTR(-EACCES);
+	filemap_invalidate_unlock_shared(inode->i_mapping);
 
-	folio = kvm_gmem_get_folio(inode, vmf->pgoff);
 	if (IS_ERR(folio)) {
 		if (PTR_ERR(folio) == -EAGAIN)
 			return VM_FAULT_RETRY;
@@ -520,6 +550,51 @@ bool __weak kvm_arch_supports_gmem_init_shared(struct kvm *kvm)
 	return true;
 }
 
+static int kvm_gmem_init_inode(struct inode *inode, loff_t size, u64 flags)
+{
+	struct gmem_inode *gi = GMEM_I(inode);
+	MA_STATE(mas, &gi->attributes, 0, (size >> PAGE_SHIFT) - 1);
+	u64 attrs;
+	int r;
+
+	inode->i_op = &kvm_gmem_iops;
+	inode->i_mapping->a_ops = &kvm_gmem_aops;
+	inode->i_mode |= S_IFREG;
+	inode->i_size = size;
+	mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
+
+	/*
+	 * guest_memfd memory is neither migratable nor swappable: set
+	 * inaccessible to gate off both.
+	 */
+	mapping_set_inaccessible(inode->i_mapping);
+	WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping));
+
+	gi->flags = flags;
+
+	mt_set_external_lock(&gi->attributes,
+			     &inode->i_mapping->invalidate_lock);
+
+	/*
+	 * Store default attributes for the entire gmem instance. Ensuring every
+	 * index is represented in the maple tree at all times simplifies the
+	 * conversion and merging logic.
+	 */
+	attrs = kvm_gmem_get_default_attributes(inode);
+
+	/*
+	 * Acquire the invalidation lock purely to make lockdep happy.  The
+	 * maple tree library expects all stores to be protected via the lock,
+	 * and the library can't know when the tree is reachable only by the
+	 * caller, as is the case here.
+	 */
+	filemap_invalidate_lock(inode->i_mapping);
+	r = mas_store_gfp(&mas, xa_mk_value(attrs), GFP_KERNEL);
+	filemap_invalidate_unlock(inode->i_mapping);
+
+	return r;
+}
+
 static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
 {
 	static const char *name = "[kvm-gmem]";
@@ -550,16 +625,9 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
 		goto err_fops;
 	}
 
-	inode->i_op = &kvm_gmem_iops;
-	inode->i_mapping->a_ops = &kvm_gmem_aops;
-	inode->i_mode |= S_IFREG;
-	inode->i_size = size;
-	mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
-	mapping_set_inaccessible(inode->i_mapping);
-	/* Unmovable mappings are supposed to be marked unevictable as well. */
-	WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping));
-
-	GMEM_I(inode)->flags = flags;
+	err = kvm_gmem_init_inode(inode, size, flags);
+	if (err)
+		goto err_inode;
 
 	file = alloc_file_pseudo(inode, kvm_gmem_mnt, name, O_RDWR, &kvm_gmem_fops);
 	if (IS_ERR(file)) {
@@ -763,9 +831,13 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
 	if (!file)
 		return -EFAULT;
 
+	filemap_invalidate_lock_shared(file_inode(file)->i_mapping);
+
 	folio = __kvm_gmem_get_pfn(file, slot, index, pfn, max_order);
-	if (IS_ERR(folio))
-		return PTR_ERR(folio);
+	if (IS_ERR(folio)) {
+		r = PTR_ERR(folio);
+		goto out;
+	}
 
 	if (!folio_test_uptodate(folio)) {
 		clear_highpage(folio_page(folio, 0));
@@ -780,6 +852,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
 	folio_unlock(folio);
 	folio_put(folio);
 
+out:
+	filemap_invalidate_unlock_shared(file_inode(file)->i_mapping);
 	return r;
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn);
@@ -909,6 +983,15 @@ static struct inode *kvm_gmem_alloc_inode(struct super_block *sb)
 
 	mpol_shared_policy_init(&gi->policy, NULL);
 
+	/*
+	 * Memory attributes are protected by the filemap invalidation lock, but
+	 * the lock structure isn't available at this time.  Immediately mark
+	 * maple tree as using external locking so that accessing the tree
+	 * before it's fully initialized results in NULL pointer dereferences
+	 * and not more subtle bugs.
+	 */
+	mt_init_flags(&gi->attributes, MT_FLAGS_LOCK_EXTERN | MT_FLAGS_USE_RCU);
+
 	gi->flags = 0;
 	INIT_LIST_HEAD(&gi->gmem_file_list);
 	return &gi->vfs_inode;
@@ -916,7 +999,26 @@ static struct inode *kvm_gmem_alloc_inode(struct super_block *sb)
 
 static void kvm_gmem_destroy_inode(struct inode *inode)
 {
-	mpol_free_shared_policy(&GMEM_I(inode)->policy);
+	struct gmem_inode *gi = GMEM_I(inode);
+
+	mpol_free_shared_policy(&gi->policy);
+
+	/*
+	 * Note!  Checking for an empty tree is functionally necessary
+	 * to avoid explosions if the tree hasn't been fully
+	 * initialized, i.e. if the inode is being destroyed before
+	 * guest_memfd can set the external lock, lockdep would find
+	 * that the tree's internal ma_lock was not held.
+	 */
+	if (!mtree_empty(&gi->attributes)) {
+		/*
+		 * Acquire the invalidation lock purely to make lockdep happy,
+		 * the inode is unreachable at this point.
+		 */
+		filemap_invalidate_lock(inode->i_mapping);
+		__mt_destroy(&gi->attributes);
+		filemap_invalidate_unlock(inode->i_mapping);
+	}
 }
 
 static void kvm_gmem_free_inode(struct inode *inode)

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 04/45] KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Rename the per-VM memory attributes Kconfig to make it explicitly about
per-VM attributes in anticipation of adding memory attributes support to
guest_memfd, at which point it will be possible (and desirable) to have
memory attributes without the per-VM support, even in x86.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/Kconfig            |  6 +++---
 arch/x86/kvm/mmu/mmu.c          |  2 +-
 arch/x86/kvm/x86.c              |  2 +-
 include/linux/kvm_host.h        |  8 ++++----
 include/trace/events/kvm.h      |  4 ++--
 virt/kvm/Kconfig                |  2 +-
 virt/kvm/kvm_main.c             | 14 +++++++-------
 8 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6beddd8a0c749..744c1f6ff03ed 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1851,7 +1851,7 @@ enum kvm_intr_type {
 	((vcpu) && (vcpu)->arch.handling_intr_from_guest && \
 	 (!!in_nmi() == ((vcpu)->arch.handling_intr_from_guest == KVM_HANDLING_NMI)))
 
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 #define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem)
 #endif
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 538ed1e803326..2f8e1b5a8a72c 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -84,7 +84,7 @@ config KVM_SW_PROTECTED_VM
 	bool "Enable support for KVM software-protected VMs"
 	depends on EXPERT
 	depends on KVM_X86 && X86_64
-	select KVM_GENERIC_MEMORY_ATTRIBUTES
+	select KVM_VM_MEMORY_ATTRIBUTES
 	help
 	  Enable support for KVM software-protected VMs.  Currently, software-
 	  protected VMs are purely a development and testing vehicle for
@@ -135,7 +135,7 @@ config KVM_INTEL_TDX
 	bool "Intel Trust Domain Extensions (TDX) support"
 	default y
 	depends on INTEL_TDX_HOST
-	select KVM_GENERIC_MEMORY_ATTRIBUTES
+	select KVM_VM_MEMORY_ATTRIBUTES
 	select HAVE_KVM_ARCH_GMEM_POPULATE
 	help
 	  Provides support for launching Intel Trust Domain Extensions (TDX)
@@ -159,7 +159,7 @@ config KVM_AMD_SEV
 	depends on KVM_AMD && X86_64
 	depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
 	select ARCH_HAS_CC_PLATFORM
-	select KVM_GENERIC_MEMORY_ATTRIBUTES
+	select KVM_VM_MEMORY_ATTRIBUTES
 	select HAVE_KVM_ARCH_GMEM_CONVERT
 	select HAVE_KVM_ARCH_GMEM_RECLAIM
 	select HAVE_KVM_ARCH_GMEM_INVALIDATE
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 947c9cd843450..b88c00e11854a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -8097,7 +8097,7 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
 		vhost_task_stop(kvm->arch.nx_huge_page_recovery_thread);
 }
 
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 static bool hugepage_test_mixed(struct kvm_memory_slot *slot, gfn_t gfn,
 				int level)
 {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 79468ddfe4736..2292249570314 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10140,7 +10140,7 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm,
 		}
 	}
 
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 	kvm_mmu_init_memslot_memory_attributes(kvm, slot);
 #endif
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b7516e19ef419..cffa16647f2ab 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -722,7 +722,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
 }
 #endif
 
-#ifndef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifndef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
 {
 	return false;
@@ -872,7 +872,7 @@ struct kvm {
 #ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
 	struct notifier_block pm_notifier;
 #endif
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 	/* Protected by slots_lock (for writes) and RCU (for reads) */
 	struct xarray mem_attr_array;
 #endif
@@ -2560,7 +2560,7 @@ static inline bool kvm_memslot_is_gmem_only(const struct kvm_memory_slot *slot)
 	return slot->flags & KVM_MEMSLOT_GMEM_ONLY;
 }
 
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn)
 {
 	return xa_to_value(xa_load(&kvm->mem_attr_array, gfn));
@@ -2582,7 +2582,7 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 {
 	return false;
 }
-#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index b282e3a867696..1ba72bd73ea2f 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -358,7 +358,7 @@ TRACE_EVENT(kvm_dirty_ring_exit,
 	TP_printk("vcpu %d", __entry->vcpu_id)
 );
 
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 /*
  * @start:	Starting address of guest memory range
  * @end:	End address of guest memory range
@@ -383,7 +383,7 @@ TRACE_EVENT(kvm_vm_set_mem_attributes,
 	TP_printk("%#016llx -- %#016llx [0x%lx]",
 		  __entry->start, __entry->end, __entry->attr)
 );
-#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
 
 TRACE_EVENT(kvm_unmap_hva_range,
 	TP_PROTO(unsigned long start, unsigned long end),
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index c3c0ee253fc77..df575449d97b5 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -100,7 +100,7 @@ config KVM_ELIDE_TLB_FLUSH_IF_YOUNG
 config KVM_MMU_LOCKLESS_AGING
        bool
 
-config KVM_GENERIC_MEMORY_ATTRIBUTES
+config KVM_VM_MEMORY_ATTRIBUTES
        bool
 
 config KVM_GUEST_MEMFD
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 65eb26a0520d8..7d5325e3cb44b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1116,7 +1116,7 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
 	spin_lock_init(&kvm->mn_invalidate_lock);
 	rcuwait_init(&kvm->mn_memslots_update_rcuwait);
 	xa_init(&kvm->vcpu_array);
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 	xa_init(&kvm->mem_attr_array);
 #endif
 
@@ -1301,7 +1301,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
 	cleanup_srcu_struct(&kvm->irq_srcu);
 	srcu_barrier(&kvm->srcu);
 	cleanup_srcu_struct(&kvm->srcu);
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 	xa_destroy(&kvm->mem_attr_array);
 #endif
 	kvm_arch_free_vm(kvm);
@@ -2419,7 +2419,7 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 }
 #endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
 
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 static u64 kvm_supported_mem_attributes(struct kvm *kvm)
 {
 	if (!kvm || kvm_arch_has_private_mem(kvm))
@@ -2624,7 +2624,7 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
 
 	return kvm_vm_set_mem_attributes(kvm, start, end, attrs->attributes);
 }
-#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
 
 struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
 {
@@ -4941,7 +4941,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
 	case KVM_CAP_SYSTEM_EVENT_DATA:
 	case KVM_CAP_DEVICE_CTRL:
 		return 1;
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 	case KVM_CAP_MEMORY_ATTRIBUTES:
 		return kvm_supported_mem_attributes(kvm);
 #endif
@@ -5345,7 +5345,7 @@ static long kvm_vm_ioctl(struct file *filp,
 		break;
 	}
 #endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 	case KVM_SET_MEMORY_ATTRIBUTES: {
 		struct kvm_memory_attributes attrs;
 
@@ -5356,7 +5356,7 @@ static long kvm_vm_ioctl(struct file *filp,
 		r = kvm_vm_ioctl_set_mem_attributes(kvm, &attrs);
 		break;
 	}
-#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
 	case KVM_CREATE_DEVICE: {
 		struct kvm_create_device cd;
 

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 05/45] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Explicitly guard reporting support for KVM_MEMORY_ATTRIBUTE_PRIVATE based
on kvm_arch_has_private_mem being #defined in anticipation of tracking
PRIVATE vs. SHARED state per-guest_memfd, not per-VM (to allow in-place
conversion).

guest_memfd support for memory attributes is expected to be unconditional
to avoid yet more macros (all architectures that support guest_memfd are
expected to use per-gmem attributes at some point), at which point
enumerating support KVM_MEMORY_ATTRIBUTE_PRIVATE based solely on memory
attributes being supported by KVM at-large would result in a system-scope
check (NULL @kvm) over-reporting support on arm64.

Give architectures full control over overriding the default definition of
kvm_arch_has_private_mem() by removing the coupling with
CONFIG_KVM_VM_MEMORY_ATTRIBUTES.

In a later patch, kvm_arch_has_private_mem() will be defined based on
whether architectural features are compiled in, and made orthogonal to
CONFIG_KVM_VM_MEMORY_ATTRIBUTES.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 include/linux/kvm_host.h | 2 +-
 virt/kvm/kvm_main.c      | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index cffa16647f2ab..b45fb80b0aca0 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -722,7 +722,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
 }
 #endif
 
-#ifndef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+#ifndef kvm_arch_has_private_mem
 static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
 {
 	return false;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7d5325e3cb44b..050757544a1cb 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2422,8 +2422,10 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 static u64 kvm_supported_mem_attributes(struct kvm *kvm)
 {
+#ifdef kvm_arch_has_private_mem
 	if (!kvm || kvm_arch_has_private_mem(kvm))
 		return KVM_MEMORY_ATTRIBUTE_PRIVATE;
+#endif
 
 	return 0;
 }

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 06/45] KVM: Rename memory attribute APIs to prepare for in-place gmem conversion

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Rename memory attribute APIs to add a "vm_" in the name in anticipation of
moving PRIVATE tracking into guest_memfd, to allow in-place conversion
between SHARED and PRIVATE.  At that point, there will effectively be two
(potential) sources of memory attributes: the VM and guest_memfd.

kvm_vm_set_mem_attributes() already has "vm" in the name to indicate that
it is a VM ioctl. Rename it to kvm_set_vm_mem_attributes() to show that it
is setting the VM's memory attributes. (Drop the VM-ioctl scoping since it
is a helper local to the file.) Update the accompanying trace function to
match.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 arch/x86/kvm/mmu/mmu.c     | 14 +++++++-------
 include/linux/kvm_host.h   | 16 ++++++++--------
 include/trace/events/kvm.h |  2 +-
 virt/kvm/kvm_main.c        | 32 ++++++++++++++++----------------
 4 files changed, 32 insertions(+), 32 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index b88c00e11854a..10e59507d252f 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -8116,8 +8116,8 @@ static void hugepage_set_mixed(struct kvm_memory_slot *slot, gfn_t gfn,
 	lpage_info_slot(gfn, slot, level)->disallow_lpage |= KVM_LPAGE_MIXED_FLAG;
 }
 
-bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
-					struct kvm_gfn_range *range)
+bool kvm_arch_pre_set_vm_memory_attributes(struct kvm *kvm,
+					   struct kvm_gfn_range *range)
 {
 	struct kvm_memory_slot *slot = range->slot;
 	int level;
@@ -8186,18 +8186,18 @@ static bool hugepage_has_attrs(struct kvm *kvm, struct kvm_memory_slot *slot,
 	const unsigned long end = start + KVM_PAGES_PER_HPAGE(level);
 
 	if (level == PG_LEVEL_2M)
-		return kvm_range_has_memory_attributes(kvm, start, end, ~0, attrs);
+		return kvm_range_has_vm_memory_attributes(kvm, start, end, ~0, attrs);
 
 	for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
 		if (hugepage_test_mixed(slot, gfn, level - 1) ||
-		    attrs != kvm_get_memory_attributes(kvm, gfn))
+		    attrs != kvm_get_vm_memory_attributes(kvm, gfn))
 			return false;
 	}
 	return true;
 }
 
-bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
-					 struct kvm_gfn_range *range)
+bool kvm_arch_post_set_vm_memory_attributes(struct kvm *kvm,
+					    struct kvm_gfn_range *range)
 {
 	unsigned long attrs = range->arg.attributes;
 	struct kvm_memory_slot *slot = range->slot;
@@ -8290,7 +8290,7 @@ void kvm_mmu_init_memslot_memory_attributes(struct kvm *kvm,
 		 * be manually checked as the attributes may already be mixed.
 		 */
 		for (gfn = start; gfn < end; gfn += nr_pages) {
-			unsigned long attrs = kvm_get_memory_attributes(kvm, gfn);
+			unsigned long attrs = kvm_get_vm_memory_attributes(kvm, gfn);
 
 			if (hugepage_has_attrs(kvm, slot, gfn, level, attrs))
 				hugepage_clear_mixed(slot, gfn, level);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b45fb80b0aca0..6ca81f5349db8 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2561,21 +2561,21 @@ static inline bool kvm_memslot_is_gmem_only(const struct kvm_memory_slot *slot)
 }
 
 #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
-static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn)
+static inline unsigned long kvm_get_vm_memory_attributes(struct kvm *kvm, gfn_t gfn)
 {
 	return xa_to_value(xa_load(&kvm->mem_attr_array, gfn));
 }
 
-bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
-				     unsigned long mask, unsigned long attrs);
-bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
-					struct kvm_gfn_range *range);
-bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
-					 struct kvm_gfn_range *range);
+bool kvm_range_has_vm_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
+					unsigned long mask, unsigned long attrs);
+bool kvm_arch_pre_set_vm_memory_attributes(struct kvm *kvm,
+					   struct kvm_gfn_range *range);
+bool kvm_arch_post_set_vm_memory_attributes(struct kvm *kvm,
+					    struct kvm_gfn_range *range);
 
 static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 {
-	return kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
+	return kvm_get_vm_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
 }
 #else
 static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index 1ba72bd73ea2f..c4d514d2350cf 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -364,7 +364,7 @@ TRACE_EVENT(kvm_dirty_ring_exit,
  * @end:	End address of guest memory range
  * @attr:	The value of the attribute being set.
  */
-TRACE_EVENT(kvm_vm_set_mem_attributes,
+TRACE_EVENT(kvm_set_vm_mem_attributes,
 	TP_PROTO(gfn_t start, gfn_t end, unsigned long attr),
 	TP_ARGS(start, end, attr),
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 050757544a1cb..91d5af7d60d0f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2420,7 +2420,7 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 #endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
 
 #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
-static u64 kvm_supported_mem_attributes(struct kvm *kvm)
+static u64 kvm_supported_vm_mem_attributes(struct kvm *kvm)
 {
 #ifdef kvm_arch_has_private_mem
 	if (!kvm || kvm_arch_has_private_mem(kvm))
@@ -2434,19 +2434,19 @@ static u64 kvm_supported_mem_attributes(struct kvm *kvm)
  * Returns true if _all_ gfns in the range [@start, @end) have attributes
  * such that the bits in @mask match @attrs.
  */
-bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
-				     unsigned long mask, unsigned long attrs)
+bool kvm_range_has_vm_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
+					unsigned long mask, unsigned long attrs)
 {
 	XA_STATE(xas, &kvm->mem_attr_array, start);
 	unsigned long index;
 	void *entry;
 
-	mask &= kvm_supported_mem_attributes(kvm);
+	mask &= kvm_supported_vm_mem_attributes(kvm);
 	if (attrs & ~mask)
 		return false;
 
 	if (end == start + 1)
-		return (kvm_get_memory_attributes(kvm, start) & mask) == attrs;
+		return (kvm_get_vm_memory_attributes(kvm, start) & mask) == attrs;
 
 	guard(rcu)();
 	if (!attrs)
@@ -2517,8 +2517,8 @@ static __always_inline void kvm_handle_gfn_range(struct kvm *kvm,
 		KVM_MMU_UNLOCK(kvm);
 }
 
-static bool kvm_pre_set_memory_attributes(struct kvm *kvm,
-					  struct kvm_gfn_range *range)
+static bool kvm_pre_set_vm_memory_attributes(struct kvm *kvm,
+					     struct kvm_gfn_range *range)
 {
 	/*
 	 * Unconditionally add the range to the invalidation set, regardless of
@@ -2533,18 +2533,18 @@ static bool kvm_pre_set_memory_attributes(struct kvm *kvm,
 	 */
 	kvm_mmu_invalidate_range_add(kvm, range->start, range->end);
 
-	return kvm_arch_pre_set_memory_attributes(kvm, range);
+	return kvm_arch_pre_set_vm_memory_attributes(kvm, range);
 }
 
 /* Set @attributes for the gfn range [@start, @end). */
-static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
+static int kvm_set_vm_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 				     unsigned long attributes)
 {
 	struct kvm_mmu_notifier_range pre_set_range = {
 		.start = start,
 		.end = end,
 		.arg.attributes = attributes,
-		.handler = kvm_pre_set_memory_attributes,
+		.handler = kvm_pre_set_vm_memory_attributes,
 		.on_lock = kvm_mmu_invalidate_start,
 		.flush_on_ret = true,
 		.may_block = true,
@@ -2553,7 +2553,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 		.start = start,
 		.end = end,
 		.arg.attributes = attributes,
-		.handler = kvm_arch_post_set_memory_attributes,
+		.handler = kvm_arch_post_set_vm_memory_attributes,
 		.on_lock = kvm_mmu_invalidate_end,
 		.may_block = true,
 	};
@@ -2563,12 +2563,12 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 
 	entry = attributes ? xa_mk_value(attributes) : NULL;
 
-	trace_kvm_vm_set_mem_attributes(start, end, attributes);
+	trace_kvm_set_vm_mem_attributes(start, end, attributes);
 
 	mutex_lock(&kvm->slots_lock);
 
 	/* Nothing to do if the entire range has the desired attributes. */
-	if (kvm_range_has_memory_attributes(kvm, start, end, ~0, attributes))
+	if (kvm_range_has_vm_memory_attributes(kvm, start, end, ~0, attributes))
 		goto out_unlock;
 
 	/*
@@ -2607,7 +2607,7 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
 	/* flags is currently not used. */
 	if (attrs->flags)
 		return -EINVAL;
-	if (attrs->attributes & ~kvm_supported_mem_attributes(kvm))
+	if (attrs->attributes & ~kvm_supported_vm_mem_attributes(kvm))
 		return -EINVAL;
 	if (attrs->size == 0 || attrs->address + attrs->size < attrs->address)
 		return -EINVAL;
@@ -2624,7 +2624,7 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
 	 */
 	BUILD_BUG_ON(sizeof(attrs->attributes) != sizeof(unsigned long));
 
-	return kvm_vm_set_mem_attributes(kvm, start, end, attrs->attributes);
+	return kvm_set_vm_mem_attributes(kvm, start, end, attrs->attributes);
 }
 #endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
 
@@ -4945,7 +4945,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
 		return 1;
 #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 	case KVM_CAP_MEMORY_ATTRIBUTES:
-		return kvm_supported_mem_attributes(kvm);
+		return kvm_supported_vm_mem_attributes(kvm);
 #endif
 #ifdef CONFIG_KVM_GUEST_MEMFD
 	case KVM_CAP_GUEST_MEMFD:

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 07/45] KVM: Rename kvm_mem_is_private() to kvm_is_private_gfn()

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Rename kvm_mem_is_private() to kvm_is_private_gfn() to prepare for in-place
conversion, where there will be two lookup functions,
kvm_vm_is_private_gfn() and kvm_gmem_is_private_gfn().

This renaming allows consistent prefixing of "vm" vs "gmem" for
kvm_*_is_private_gfn(), as opposed to kvm_gmem_mem_is_private(), which
looks like a typo.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 arch/x86/kvm/mmu/mmu.c   | 12 ++++++------
 arch/x86/kvm/svm/sev.c   |  2 +-
 include/linux/kvm_host.h |  4 ++--
 virt/kvm/guest_memfd.c   |  2 +-
 4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 10e59507d252f..62f751952ad8a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3421,7 +3421,7 @@ int kvm_mmu_max_mapping_level(struct kvm *kvm, struct kvm_page_fault *fault,
 		is_private = fault->is_private;
 	} else {
 		max_level = PG_LEVEL_NUM;
-		is_private = kvm_mem_is_private(kvm, gfn);
+		is_private = kvm_is_private_gfn(kvm, gfn);
 	}
 
 	max_level = min(max_level, max_huge_page_level);
@@ -3634,13 +3634,13 @@ static bool page_fault_can_be_fast(struct kvm *kvm, struct kvm_page_fault *fault
 	 * guest spinning on a #PF indefinitely, so don't attempt the fast path
 	 * in this case.
 	 *
-	 * Note that the kvm_mem_is_private() check might race with an
+	 * Note that the kvm_is_private_gfn() check might race with an
 	 * attribute update, but this will either result in the guest spinning
 	 * on RET_PF_SPURIOUS until the update completes, or an actual spurious
 	 * case might go down the slow path. Either case will resolve itself.
 	 */
 	if (kvm->arch.has_private_mem &&
-	    fault->is_private != kvm_mem_is_private(kvm, fault->gfn))
+	    fault->is_private != kvm_is_private_gfn(kvm, fault->gfn))
 		return false;
 
 	/*
@@ -4708,7 +4708,7 @@ static int kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,
 	 * Now that we have a snapshot of mmu_invalidate_seq we can check for a
 	 * private vs. shared mismatch.
 	 */
-	if (fault->is_private != kvm_mem_is_private(kvm, fault->gfn)) {
+	if (fault->is_private != kvm_is_private_gfn(kvm, fault->gfn)) {
 		kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
 		return -EFAULT;
 	}
@@ -5111,7 +5111,7 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
 
 	direct_bits = 0;
 	if (kvm_arch_has_private_mem(vcpu->kvm) &&
-	    kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(range->gpa)))
+	    kvm_is_private_gfn(vcpu->kvm, gpa_to_gfn(range->gpa)))
 		error_code |= PFERR_PRIVATE_ACCESS;
 	else
 		direct_bits = gfn_to_gpa(kvm_gfn_direct_bits(vcpu->kvm));
@@ -6584,7 +6584,7 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
 	if (IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) &&
 	    !(error_code & PFERR_RSVD_MASK) &&
 	    vcpu->kvm->arch.vm_type == KVM_X86_SW_PROTECTED_VM &&
-	    kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(cr2_or_gpa)))
+	    kvm_is_private_gfn(vcpu->kvm, gpa_to_gfn(cr2_or_gpa)))
 		error_code |= PFERR_PRIVATE_ACCESS;
 
 	r = RET_PF_INVALID;
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0a887f8e05d3a..dff684b88f153 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -5030,7 +5030,7 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
 	 * userspace via KVM_EXIT_MEMORY_FAULT events, however, so RMP faults
 	 * for shared pages should not end up here.
 	 */
-	if (!kvm_mem_is_private(kvm, gfn)) {
+	if (!kvm_is_private_gfn(kvm, gfn)) {
 		pr_warn_ratelimited("SEV: Unexpected RMP fault for non-private GPA 0x%llx\n",
 				    gpa);
 		return;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6ca81f5349db8..9b97266f61ec8 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2573,12 +2573,12 @@ bool kvm_arch_pre_set_vm_memory_attributes(struct kvm *kvm,
 bool kvm_arch_post_set_vm_memory_attributes(struct kvm *kvm,
 					    struct kvm_gfn_range *range);
 
-static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 {
 	return kvm_get_vm_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
 }
 #else
-static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 {
 	return false;
 }
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index e32ac2c28cbef..ce5efcacda36e 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -879,7 +879,7 @@ static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot,
 
 	folio_unlock(folio);
 
-	if (!kvm_mem_is_private(kvm, gfn)) {
+	if (!kvm_is_private_gfn(kvm, gfn)) {
 		ret = -EINVAL;
 		goto out_put_folio;
 	}

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 07/45] KVM: Rename kvm_mem_is_private() to kvm_is_private_gfn()

[Fuad Tabba]

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Ackerley Tng <ackerleytng@google.com>
>
> Rename kvm_mem_is_private() to kvm_is_private_gfn() to prepare for in-place
> conversion, where there will be two lookup functions,
> kvm_vm_is_private_gfn() and kvm_gmem_is_private_gfn().
>
> This renaming allows consistent prefixing of "vm" vs "gmem" for
> kvm_*_is_private_gfn(), as opposed to kvm_gmem_mem_is_private(), which
> looks like a typo.
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

Cheers,
/fuad

> ---
>  arch/x86/kvm/mmu/mmu.c   | 12 ++++++------
>  arch/x86/kvm/svm/sev.c   |  2 +-
>  include/linux/kvm_host.h |  4 ++--
>  virt/kvm/guest_memfd.c   |  2 +-
>  4 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 10e59507d252f..62f751952ad8a 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3421,7 +3421,7 @@ int kvm_mmu_max_mapping_level(struct kvm *kvm, struct kvm_page_fault *fault,
>                 is_private = fault->is_private;
>         } else {
>                 max_level = PG_LEVEL_NUM;
> -               is_private = kvm_mem_is_private(kvm, gfn);
> +               is_private = kvm_is_private_gfn(kvm, gfn);
>         }
>
>         max_level = min(max_level, max_huge_page_level);
> @@ -3634,13 +3634,13 @@ static bool page_fault_can_be_fast(struct kvm *kvm, struct kvm_page_fault *fault
>          * guest spinning on a #PF indefinitely, so don't attempt the fast path
>          * in this case.
>          *
> -        * Note that the kvm_mem_is_private() check might race with an
> +        * Note that the kvm_is_private_gfn() check might race with an
>          * attribute update, but this will either result in the guest spinning
>          * on RET_PF_SPURIOUS until the update completes, or an actual spurious
>          * case might go down the slow path. Either case will resolve itself.
>          */
>         if (kvm->arch.has_private_mem &&
> -           fault->is_private != kvm_mem_is_private(kvm, fault->gfn))
> +           fault->is_private != kvm_is_private_gfn(kvm, fault->gfn))
>                 return false;
>
>         /*
> @@ -4708,7 +4708,7 @@ static int kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,
>          * Now that we have a snapshot of mmu_invalidate_seq we can check for a
>          * private vs. shared mismatch.
>          */
> -       if (fault->is_private != kvm_mem_is_private(kvm, fault->gfn)) {
> +       if (fault->is_private != kvm_is_private_gfn(kvm, fault->gfn)) {
>                 kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
>                 return -EFAULT;
>         }
> @@ -5111,7 +5111,7 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
>
>         direct_bits = 0;
>         if (kvm_arch_has_private_mem(vcpu->kvm) &&
> -           kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(range->gpa)))
> +           kvm_is_private_gfn(vcpu->kvm, gpa_to_gfn(range->gpa)))
>                 error_code |= PFERR_PRIVATE_ACCESS;
>         else
>                 direct_bits = gfn_to_gpa(kvm_gfn_direct_bits(vcpu->kvm));
> @@ -6584,7 +6584,7 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
>         if (IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) &&
>             !(error_code & PFERR_RSVD_MASK) &&
>             vcpu->kvm->arch.vm_type == KVM_X86_SW_PROTECTED_VM &&
> -           kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(cr2_or_gpa)))
> +           kvm_is_private_gfn(vcpu->kvm, gpa_to_gfn(cr2_or_gpa)))
>                 error_code |= PFERR_PRIVATE_ACCESS;
>
>         r = RET_PF_INVALID;
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 0a887f8e05d3a..dff684b88f153 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -5030,7 +5030,7 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code)
>          * userspace via KVM_EXIT_MEMORY_FAULT events, however, so RMP faults
>          * for shared pages should not end up here.
>          */
> -       if (!kvm_mem_is_private(kvm, gfn)) {
> +       if (!kvm_is_private_gfn(kvm, gfn)) {
>                 pr_warn_ratelimited("SEV: Unexpected RMP fault for non-private GPA 0x%llx\n",
>                                     gpa);
>                 return;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 6ca81f5349db8..9b97266f61ec8 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2573,12 +2573,12 @@ bool kvm_arch_pre_set_vm_memory_attributes(struct kvm *kvm,
>  bool kvm_arch_post_set_vm_memory_attributes(struct kvm *kvm,
>                                             struct kvm_gfn_range *range);
>
> -static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
> +static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
>  {
>         return kvm_get_vm_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
>  }
>  #else
> -static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
> +static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
>  {
>         return false;
>  }
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index e32ac2c28cbef..ce5efcacda36e 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -879,7 +879,7 @@ static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot,
>
>         folio_unlock(folio);
>
> -       if (!kvm_mem_is_private(kvm, gfn)) {
> +       if (!kvm_is_private_gfn(kvm, gfn)) {
>                 ret = -EINVAL;
>                 goto out_put_folio;
>         }
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

Re: [PATCH v12 07/45] KVM: Rename kvm_mem_is_private() to kvm_is_private_gfn()

[Binbin Wu]

On 8/31/2026 8:25 AM, Ackerley Tng via B4 Relay wrote:
> From: Ackerley Tng <ackerleytng@google.com>
> 
> Rename kvm_mem_is_private() to kvm_is_private_gfn() to prepare for in-place
> conversion, where there will be two lookup functions,
> kvm_vm_is_private_gfn() and kvm_gmem_is_private_gfn().
> 
> This renaming allows consistent prefixing of "vm" vs "gmem" for
> kvm_*_is_private_gfn(), as opposed to kvm_gmem_mem_is_private(), which
> looks like a typo.
> 
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>

[PATCH v12 08/45] KVM: Provide generic interface for checking memory private/shared status

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Introduce a generic kvm_is_private_gfn() interface using a static call to
determine if a GFN is private. This allows the implementation for checking
a GFN's private/shared status to be set at runtime.

In preparation for choosing implementations between a guest_memfd lookup
and the existing VM attribute lookup, rename the existing
VM-attribute-based check to kvm_vm_is_private_gfn() to emphasize that it
looks up VM attributes.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 include/linux/kvm_host.h | 14 ++++++++++++--
 virt/kvm/kvm_main.c      | 15 +++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 9b97266f61ec8..3579feb631775 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2573,16 +2573,26 @@ bool kvm_arch_pre_set_vm_memory_attributes(struct kvm *kvm,
 bool kvm_arch_post_set_vm_memory_attributes(struct kvm *kvm,
 					    struct kvm_gfn_range *range);
 
-static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
+static inline bool kvm_vm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 {
 	return kvm_get_vm_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
 }
+#endif  /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
+
+#ifdef kvm_arch_has_private_mem
+typedef bool (kvm_is_private_gfn_t)(struct kvm *kvm, gfn_t gfn);
+DECLARE_STATIC_CALL(__kvm_is_private_gfn, kvm_is_private_gfn_t);
+
+static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
+{
+	return static_call(__kvm_is_private_gfn)(kvm, gfn);
+}
 #else
 static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 {
 	return false;
 }
-#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
+#endif /* kvm_arch_has_private_mem */
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 91d5af7d60d0f..78278730b2ae4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2628,6 +2628,20 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
 }
 #endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
 
+#ifdef kvm_arch_has_private_mem
+DEFINE_STATIC_CALL_RET0(__kvm_is_private_gfn, kvm_is_private_gfn_t);
+EXPORT_STATIC_CALL_GPL(__kvm_is_private_gfn);
+
+static void kvm_init_memory_attributes(void)
+{
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+	static_call_update(__kvm_is_private_gfn, kvm_vm_is_private_gfn);
+#endif
+}
+#else
+static void kvm_init_memory_attributes(void) { }
+#endif
+
 struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
 {
 	return __gfn_to_memslot(kvm_memslots(kvm), gfn);
@@ -6541,6 +6555,7 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
 	kvm_preempt_ops.sched_in = kvm_sched_in;
 	kvm_preempt_ops.sched_out = kvm_sched_out;
 
+	kvm_init_memory_attributes();
 	kvm_init_debug();
 
 	r = kvm_vfio_ops_init();

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 09/45] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Stub in global variable to enable in-place guest_memfd private<=>shared
memory conversion, which will eventually be exposed to userspace via a
module param, and wire up the __kvm_is_private_gfn() static call to the
guest_memfd version when in-place conversion is enabled, i.e. when gmem is
the sole authority on private vs. shared memory.

Cc: Fuad Tabba <tabba@google.com>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 Documentation/virt/kvm/api.rst |  7 +++++++
 include/linux/kvm_host.h       |  6 ++++++
 virt/kvm/guest_memfd.c         | 26 ++++++++++++++++++++++++++
 virt/kvm/kvm_main.c            | 12 +++++++++++-
 4 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index e0430cc750c9e..90a29424c54c8 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6382,6 +6382,11 @@ KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated
 on-demand.
 
 When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes
+userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the
+sole authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD`
+to find out more about the creation-time shared/private status.
+
+If in-place conversion is disabled, KVM selects shared vs. private, i.e consumes
 userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE
 state.  At VM creation time, all memory is shared, i.e. the PRIVATE attribute
 is '0' for all gfns.  Userspace can control whether memory is shared/private by
@@ -6429,6 +6434,8 @@ the state of a gfn/page as needed.
 
 The "flags" field is reserved for future extensions and must be '0'.
 
+.. _KVM_CREATE_GUEST_MEMFD:
+
 4.142 KVM_CREATE_GUEST_MEMFD
 ----------------------------
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3579feb631775..b0110143d2ff8 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2580,6 +2580,8 @@ static inline bool kvm_vm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 #endif  /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
 
 #ifdef kvm_arch_has_private_mem
+extern bool gmem_in_place_conversion;
+
 typedef bool (kvm_is_private_gfn_t)(struct kvm *kvm, gfn_t gfn);
 DECLARE_STATIC_CALL(__kvm_is_private_gfn, kvm_is_private_gfn_t);
 
@@ -2588,6 +2590,8 @@ static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 	return static_call(__kvm_is_private_gfn)(kvm, gfn);
 }
 #else
+#define gmem_in_place_conversion false
+
 static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 {
 	return false;
@@ -2595,6 +2599,8 @@ static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 #endif /* kvm_arch_has_private_mem */
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
+bool kvm_gmem_is_private_gfn(struct kvm *kvm, gfn_t gfn);
+
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
 		     gfn_t gfn, kvm_pfn_t *pfn, int *max_order);
 #else
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index ce5efcacda36e..cd966eef45b69 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -478,6 +478,32 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma)
 	return 0;
 }
 
+bool kvm_gmem_is_private_gfn(struct kvm *kvm, gfn_t gfn)
+{
+	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
+	struct inode *inode;
+
+	if (!slot)
+		return 0;
+
+	CLASS(gmem_get_file, file)(slot);
+	if (!file)
+		return 0;
+
+	inode = file_inode(file);
+
+	/*
+	 * Rely on the maple tree's internal RCU lock to ensure a stable result.
+	 * This result can become stale as soon as the lock is dropped, so the
+	 * caller _must_ protect consumption of private vs. shared either by
+	 * holding guest_memfd's invalidate lock for the entire duration, or by
+	 * checking mmu_invalidate_retry_gfn() under mmu_lock to serialize
+	 * against concurrent attribute updates.
+	 */
+	return kvm_gmem_is_private_mem(inode, kvm_gmem_get_index(slot, gfn));
+}
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_is_private_gfn);
+
 static struct file_operations kvm_gmem_fops = {
 	.mmap		= kvm_gmem_mmap,
 	.open		= generic_file_open,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 78278730b2ae4..46d2e123448c2 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -102,6 +102,10 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(halt_poll_ns_shrink);
 static bool __ro_after_init allow_unsafe_mappings;
 module_param(allow_unsafe_mappings, bool, 0444);
 
+#ifdef kvm_arch_has_private_mem
+bool __ro_after_init gmem_in_place_conversion = false;
+#endif
+
 /*
  * Ordering of locks:
  *
@@ -2423,6 +2427,9 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 static u64 kvm_supported_vm_mem_attributes(struct kvm *kvm)
 {
 #ifdef kvm_arch_has_private_mem
+	if (gmem_in_place_conversion)
+		return 0;
+
 	if (!kvm || kvm_arch_has_private_mem(kvm))
 		return KVM_MEMORY_ATTRIBUTE_PRIVATE;
 #endif
@@ -2634,8 +2641,11 @@ EXPORT_STATIC_CALL_GPL(__kvm_is_private_gfn);
 
 static void kvm_init_memory_attributes(void)
 {
+	if (gmem_in_place_conversion)
+		static_call_update(__kvm_is_private_gfn, kvm_gmem_is_private_gfn);
 #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
-	static_call_update(__kvm_is_private_gfn, kvm_vm_is_private_gfn);
+	else
+		static_call_update(__kvm_is_private_gfn, kvm_vm_is_private_gfn);
 #endif
 }
 #else

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 09/45] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion

[Fuad Tabba]

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Sean Christopherson <seanjc@google.com>
>
> Stub in global variable to enable in-place guest_memfd private<=>shared
> memory conversion, which will eventually be exposed to userspace via a
> module param, and wire up the __kvm_is_private_gfn() static call to the
> guest_memfd version when in-place conversion is enabled, i.e. when gmem is
> the sole authority on private vs. shared memory.
>
> Cc: Fuad Tabba <tabba@google.com>
> Cc: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Co-developed-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

Cheers,
/fuad


> ---
>  Documentation/virt/kvm/api.rst |  7 +++++++
>  include/linux/kvm_host.h       |  6 ++++++
>  virt/kvm/guest_memfd.c         | 26 ++++++++++++++++++++++++++
>  virt/kvm/kvm_main.c            | 12 +++++++++++-
>  4 files changed, 50 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index e0430cc750c9e..90a29424c54c8 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6382,6 +6382,11 @@ KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated
>  on-demand.
>
>  When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes
> +userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the
> +sole authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD`
> +to find out more about the creation-time shared/private status.
> +
> +If in-place conversion is disabled, KVM selects shared vs. private, i.e consumes
>  userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE
>  state.  At VM creation time, all memory is shared, i.e. the PRIVATE attribute
>  is '0' for all gfns.  Userspace can control whether memory is shared/private by
> @@ -6429,6 +6434,8 @@ the state of a gfn/page as needed.
>
>  The "flags" field is reserved for future extensions and must be '0'.
>
> +.. _KVM_CREATE_GUEST_MEMFD:
> +
>  4.142 KVM_CREATE_GUEST_MEMFD
>  ----------------------------
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 3579feb631775..b0110143d2ff8 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2580,6 +2580,8 @@ static inline bool kvm_vm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
>  #endif  /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
>
>  #ifdef kvm_arch_has_private_mem
> +extern bool gmem_in_place_conversion;
> +
>  typedef bool (kvm_is_private_gfn_t)(struct kvm *kvm, gfn_t gfn);
>  DECLARE_STATIC_CALL(__kvm_is_private_gfn, kvm_is_private_gfn_t);
>
> @@ -2588,6 +2590,8 @@ static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
>         return static_call(__kvm_is_private_gfn)(kvm, gfn);
>  }
>  #else
> +#define gmem_in_place_conversion false
> +
>  static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
>  {
>         return false;
> @@ -2595,6 +2599,8 @@ static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
>  #endif /* kvm_arch_has_private_mem */
>
>  #ifdef CONFIG_KVM_GUEST_MEMFD
> +bool kvm_gmem_is_private_gfn(struct kvm *kvm, gfn_t gfn);
> +
>  int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
>                      gfn_t gfn, kvm_pfn_t *pfn, int *max_order);
>  #else
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index ce5efcacda36e..cd966eef45b69 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -478,6 +478,32 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma)
>         return 0;
>  }
>
> +bool kvm_gmem_is_private_gfn(struct kvm *kvm, gfn_t gfn)
> +{
> +       struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
> +       struct inode *inode;
> +
> +       if (!slot)
> +               return 0;
> +
> +       CLASS(gmem_get_file, file)(slot);
> +       if (!file)
> +               return 0;
> +
> +       inode = file_inode(file);
> +
> +       /*
> +        * Rely on the maple tree's internal RCU lock to ensure a stable result.
> +        * This result can become stale as soon as the lock is dropped, so the
> +        * caller _must_ protect consumption of private vs. shared either by
> +        * holding guest_memfd's invalidate lock for the entire duration, or by
> +        * checking mmu_invalidate_retry_gfn() under mmu_lock to serialize
> +        * against concurrent attribute updates.
> +        */
> +       return kvm_gmem_is_private_mem(inode, kvm_gmem_get_index(slot, gfn));
> +}
> +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_is_private_gfn);
> +
>  static struct file_operations kvm_gmem_fops = {
>         .mmap           = kvm_gmem_mmap,
>         .open           = generic_file_open,
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 78278730b2ae4..46d2e123448c2 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -102,6 +102,10 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(halt_poll_ns_shrink);
>  static bool __ro_after_init allow_unsafe_mappings;
>  module_param(allow_unsafe_mappings, bool, 0444);
>
> +#ifdef kvm_arch_has_private_mem
> +bool __ro_after_init gmem_in_place_conversion = false;
> +#endif
> +
>  /*
>   * Ordering of locks:
>   *
> @@ -2423,6 +2427,9 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
>  static u64 kvm_supported_vm_mem_attributes(struct kvm *kvm)
>  {
>  #ifdef kvm_arch_has_private_mem
> +       if (gmem_in_place_conversion)
> +               return 0;
> +
>         if (!kvm || kvm_arch_has_private_mem(kvm))
>                 return KVM_MEMORY_ATTRIBUTE_PRIVATE;
>  #endif
> @@ -2634,8 +2641,11 @@ EXPORT_STATIC_CALL_GPL(__kvm_is_private_gfn);
>
>  static void kvm_init_memory_attributes(void)
>  {
> +       if (gmem_in_place_conversion)
> +               static_call_update(__kvm_is_private_gfn, kvm_gmem_is_private_gfn);
>  #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
> -       static_call_update(__kvm_is_private_gfn, kvm_vm_is_private_gfn);
> +       else
> +               static_call_update(__kvm_is_private_gfn, kvm_vm_is_private_gfn);
>  #endif
>  }
>  #else
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

Re: [PATCH v12 09/45] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion

[Binbin Wu]

On 8/31/2026 8:25 AM, Ackerley Tng via B4 Relay wrote:
> From: Sean Christopherson <seanjc@google.com>
> 
> Stub in global variable to enable in-place guest_memfd private<=>shared
> memory conversion, which will eventually be exposed to userspace via a
> module param, and wire up the __kvm_is_private_gfn() static call to the
> guest_memfd version when in-place conversion is enabled, i.e. when gmem is
> the sole authority on private vs. shared memory.
> 
> Cc: Fuad Tabba <tabba@google.com>
> Cc: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Co-developed-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>

One nit below.

> ---
>  Documentation/virt/kvm/api.rst |  7 +++++++
>  include/linux/kvm_host.h       |  6 ++++++
>  virt/kvm/guest_memfd.c         | 26 ++++++++++++++++++++++++++
>  virt/kvm/kvm_main.c            | 12 +++++++++++-
>  4 files changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index e0430cc750c9e..90a29424c54c8 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6382,6 +6382,11 @@ KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated
>  on-demand.
>  
>  When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes
> +userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the
> +sole authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD`
> +to find out more about the creation-time shared/private status.
> +
> +If in-place conversion is disabled, KVM selects shared vs. private, i.e consumes

Nit: i.e -> i.e.
>  userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE
>  state.  At VM creation time, all memory is shared, i.e. the PRIVATE attribute
>  is '0' for all gfns.  Userspace can control whether memory is shared/private by
> @@ -6429,6 +6434,8 @@ the state of a gfn/page as needed.
>  

[PATCH v12 10/45] KVM: Consolidate private memory and guest_memfd ifdeffery in kvm_host.h

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Move the kvm_arch_has_private_mem() stub and a few guest_memfd function
definitions/declarations "down" in kvm_host.h to utilize existing #ifdefs,
and so that related code is clustered together.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 include/linux/kvm_host.h | 37 ++++++++++++++++---------------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b0110143d2ff8..ab87effdd221f 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -722,27 +722,6 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
 }
 #endif
 
-#ifndef kvm_arch_has_private_mem
-static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
-{
-	return false;
-}
-#endif
-
-#ifdef CONFIG_KVM_GUEST_MEMFD
-bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm);
-
-static inline u64 kvm_gmem_get_supported_flags(struct kvm *kvm)
-{
-	u64 flags = GUEST_MEMFD_FLAG_MMAP;
-
-	if (!kvm || kvm_arch_supports_gmem_init_shared(kvm))
-		flags |= GUEST_MEMFD_FLAG_INIT_SHARED;
-
-	return flags;
-}
-#endif
-
 #ifndef kvm_arch_has_readonly_mem
 static inline bool kvm_arch_has_readonly_mem(struct kvm *kvm)
 {
@@ -2592,6 +2571,11 @@ static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 #else
 #define gmem_in_place_conversion false
 
+static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
+{
+	return false;
+}
+
 static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 {
 	return false;
@@ -2600,6 +2584,17 @@ static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
 bool kvm_gmem_is_private_gfn(struct kvm *kvm, gfn_t gfn);
+bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm);
+
+static inline u64 kvm_gmem_get_supported_flags(struct kvm *kvm)
+{
+	u64 flags = GUEST_MEMFD_FLAG_MMAP;
+
+	if (!kvm || kvm_arch_supports_gmem_init_shared(kvm))
+		flags |= GUEST_MEMFD_FLAG_INIT_SHARED;
+
+	return flags;
+}
 
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
 		     gfn_t gfn, kvm_pfn_t *pfn, int *max_order);

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 11/45] KVM: guest_memfd: Invalidate both SHARED and PRIVATE mappings for in-place conversions

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

When removing one or more folios from a guest_memfd instance, invalidate
both SHARED and PRIVATE mappings if in-place conversion is enabled, because
stating the obvious, KVM needs to ensure that all mappings to the folio(s)
are dropped.

Opportunistically rename the helper to capture that it returns a filter for
all gfns in anticipation of zapping only the previous mapping types on
conversion.  I.e. when doing in-place conversion to PRIVATE, only SHARED
mappings need to be zapped (ignoring that KVM would ideally not invalidate
ranges whose attributes aren't changing in the first place).

Note, precisely zapping only the possible mapping types when in-place
conversion is disabled is important for functional correctness, not just
for performance.  Specifically, if KVM zaps both when SHARED vs. PRIVATE is
tracked per-VM, then a PUNCH_HOLE operation on a PRIVATE guest_memfd will
incorrectly zap SHARED mappings that have nothing to do with that gmem
instance (because they're mapped via a VMA, not a gmem fd).

The incorrect over-zapping of SHARED memory that doesn't belong to the gmem
fd requesting the zapping will be resolved in a later patch, where, if
in-place conversion is enabled, KVM will use both shared and private memory
from the guest_memfd. If both shared and private memory are from the
guest_memfd, invalidation will only zap memory belonging to the given gmem
instance.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 virt/kvm/guest_memfd.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index cd966eef45b69..0afe1468d2d9d 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -139,8 +139,11 @@ static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index)
 	return folio;
 }
 
-static enum kvm_gfn_range_filter kvm_gmem_get_invalidate_filter(struct inode *inode)
+static enum kvm_gfn_range_filter kvm_gmem_get_all_gfns_filter(struct inode *inode)
 {
+	if (gmem_in_place_conversion)
+		return KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;
+
 	if (GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED)
 		return KVM_FILTER_SHARED;
 
@@ -191,11 +194,9 @@ static void __kvm_gmem_invalidate_start(struct gmem_file *f, pgoff_t start,
 static void kvm_gmem_invalidate_start(struct inode *inode, pgoff_t start,
 				      pgoff_t end)
 {
-	enum kvm_gfn_range_filter attr_filter;
+	enum kvm_gfn_range_filter attr_filter = kvm_gmem_get_all_gfns_filter(inode);
 	struct gmem_file *f;
 
-	attr_filter = kvm_gmem_get_invalidate_filter(inode);
-
 	kvm_gmem_for_each_file(f, inode)
 		__kvm_gmem_invalidate_start(f, start, end, attr_filter);
 }
@@ -347,7 +348,7 @@ static int kvm_gmem_release(struct inode *inode, struct file *file)
 	 * memory, as its lifetime is associated with the inode, not the file.
 	 */
 	__kvm_gmem_invalidate_start(f, 0, -1ul,
-				    kvm_gmem_get_invalidate_filter(inode));
+				    kvm_gmem_get_all_gfns_filter(inode));
 	__kvm_gmem_invalidate_end(f, 0, -1ul);
 
 	list_del(&f->entry);

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 11/45] KVM: guest_memfd: Invalidate both SHARED and PRIVATE mappings for in-place conversions

[Fuad Tabba]

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Sean Christopherson <seanjc@google.com>
>
> When removing one or more folios from a guest_memfd instance, invalidate
> both SHARED and PRIVATE mappings if in-place conversion is enabled, because
> stating the obvious, KVM needs to ensure that all mappings to the folio(s)
> are dropped.
>
> Opportunistically rename the helper to capture that it returns a filter for
> all gfns in anticipation of zapping only the previous mapping types on
> conversion.  I.e. when doing in-place conversion to PRIVATE, only SHARED
> mappings need to be zapped (ignoring that KVM would ideally not invalidate
> ranges whose attributes aren't changing in the first place).
>
> Note, precisely zapping only the possible mapping types when in-place
> conversion is disabled is important for functional correctness, not just
> for performance.  Specifically, if KVM zaps both when SHARED vs. PRIVATE is
> tracked per-VM, then a PUNCH_HOLE operation on a PRIVATE guest_memfd will
> incorrectly zap SHARED mappings that have nothing to do with that gmem
> instance (because they're mapped via a VMA, not a gmem fd).
>
> The incorrect over-zapping of SHARED memory that doesn't belong to the gmem
> fd requesting the zapping will be resolved in a later patch, where, if
> in-place conversion is enabled, KVM will use both shared and private memory
> from the guest_memfd. If both shared and private memory are from the
> guest_memfd, invalidation will only zap memory belonging to the given gmem
> instance.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

Cheers,
/fuad

> ---
>  virt/kvm/guest_memfd.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index cd966eef45b69..0afe1468d2d9d 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -139,8 +139,11 @@ static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index)
>         return folio;
>  }
>
> -static enum kvm_gfn_range_filter kvm_gmem_get_invalidate_filter(struct inode *inode)
> +static enum kvm_gfn_range_filter kvm_gmem_get_all_gfns_filter(struct inode *inode)
>  {
> +       if (gmem_in_place_conversion)
> +               return KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;
> +
>         if (GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED)
>                 return KVM_FILTER_SHARED;
>
> @@ -191,11 +194,9 @@ static void __kvm_gmem_invalidate_start(struct gmem_file *f, pgoff_t start,
>  static void kvm_gmem_invalidate_start(struct inode *inode, pgoff_t start,
>                                       pgoff_t end)
>  {
> -       enum kvm_gfn_range_filter attr_filter;
> +       enum kvm_gfn_range_filter attr_filter = kvm_gmem_get_all_gfns_filter(inode);
>         struct gmem_file *f;
>
> -       attr_filter = kvm_gmem_get_invalidate_filter(inode);
> -
>         kvm_gmem_for_each_file(f, inode)
>                 __kvm_gmem_invalidate_start(f, start, end, attr_filter);
>  }
> @@ -347,7 +348,7 @@ static int kvm_gmem_release(struct inode *inode, struct file *file)
>          * memory, as its lifetime is associated with the inode, not the file.
>          */
>         __kvm_gmem_invalidate_start(f, 0, -1ul,
> -                                   kvm_gmem_get_invalidate_filter(inode));
> +                                   kvm_gmem_get_all_gfns_filter(inode));
>         __kvm_gmem_invalidate_end(f, 0, -1ul);
>
>         list_del(&f->entry);
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

Re: [PATCH v12 11/45] KVM: guest_memfd: Invalidate both SHARED and PRIVATE mappings for in-place conversions

[Binbin Wu]

On 8/31/2026 8:25 AM, Ackerley Tng via B4 Relay wrote:
> From: Sean Christopherson <seanjc@google.com>
> 
> When removing one or more folios from a guest_memfd instance, invalidate
> both SHARED and PRIVATE mappings if in-place conversion is enabled, because
> stating the obvious, KVM needs to ensure that all mappings to the folio(s)
> are dropped.
> 
> Opportunistically rename the helper to capture that it returns a filter for
> all gfns in anticipation of zapping only the previous mapping types on
> conversion.  I.e. when doing in-place conversion to PRIVATE, only SHARED
> mappings need to be zapped (ignoring that KVM would ideally not invalidate
> ranges whose attributes aren't changing in the first place).
> 
> Note, precisely zapping only the possible mapping types when in-place
> conversion is disabled is important for functional correctness, not just
> for performance.  Specifically, if KVM zaps both when SHARED vs. PRIVATE is
> tracked per-VM, then a PUNCH_HOLE operation on a PRIVATE guest_memfd will
> incorrectly zap SHARED mappings that have nothing to do with that gmem
> instance (because they're mapped via a VMA, not a gmem fd).
> 
> The incorrect over-zapping of SHARED memory that doesn't belong to the gmem
> fd requesting the zapping will be resolved in a later patch, where, if
> in-place conversion is enabled, KVM will use both shared and private memory
> from the guest_memfd. If both shared and private memory are from the
> guest_memfd, invalidation will only zap memory belonging to the given gmem
> instance.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>

[PATCH v12 12/45] KVM: guest_memfd: Always fault from guest_memfd if in-place conversion is enabled

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

If a guest_memfd memslot is created but the guest_memfd does not have the
GUEST_MEMFD_FLAG_MMAP set, KVM still fulfils guest faults by looking up the
memslot's userspace_addr.

Set KVM_MEMSLOT_GMEM_ONLY if in-place conversion is enabled so that the
guest_memfd's memory will be used for both shared and private memory. With
in-place conversion, guest_memfd will be the only backing memory for the
memslot.

No validation is performed to require userspace_addr to be a mapping from
the associated guest_memfd because even after validation, userspace is free
to remap something else at the provided userspace_addr.

userspace_addr will still be used by functions like kvm_read_guest(), and
if userspace_addr does not match up with the corresponding memory in the
memslot's guest_memfd (whether userspace_addr points to the wrong offset or
some non-guest_memfd memory, etc), that is a user error.

Requiring both shared and private memory to come from the only associated
guest_memfd simplifies invalidation in stage 2 page tables. On a PUNCH_HOLE
operation on a guest_memfd, the invalidation is now guaranteed to be
invalidating only memory mapped from the given guest_memfd.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 Documentation/virt/kvm/api.rst | 22 ++++++++++++++--------
 virt/kvm/guest_memfd.c         |  2 +-
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 90a29424c54c8..668886f50024d 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6381,10 +6381,16 @@ mapping for userspace_addr is not required to be valid/populated at the time of
 KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated
 on-demand.
 
-When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes
-userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the
-sole authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD`
-to find out more about the creation-time shared/private status.
+When mapping a gfn into the guest, guest faults are always serviced from
+guest_memfd regardless of whether memory is shared or private.  KVM determines
+shared vs. private based on the state in guest_memfd, which is the sole
+authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD` to
+find out more about the creation-time shared/private status.
+
+userspace_addr is expected to be the mmap()-ed address corresponding to the
+right offset within the guest_memfd. Any mismatch between userspace_addr and
+guest_memfd is not validated and is a user error. userspace_addr is only used
+for host-side guest accesses such as kvm_read_guest().
 
 If in-place conversion is disabled, KVM selects shared vs. private, i.e consumes
 userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE
@@ -6490,10 +6496,10 @@ specified via KVM_CREATE_GUEST_MEMFD.  Currently defined flags:
                                page tables. Private memory cannot.
   ============================ ================================================
 
-When the KVM MMU performs a PFN lookup to service a guest fault and the backing
-guest_memfd has the GUEST_MEMFD_FLAG_MMAP set, then the fault will always be
-consumed from guest_memfd, regardless of whether it is a shared or a private
-fault.
+When the KVM MMU performs a PFN lookup to service a guest fault, the fault will
+always be consumed from guest_memfd, regardless of whether it is a shared or a
+private fault (unless in-place conversion is disabled and the backing
+guest_memfd does not have the GUEST_MEMFD_FLAG_MMAP flag set).
 
 See KVM_SET_USER_MEMORY_REGION2 for additional details.
 
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 0afe1468d2d9d..e41802944756b 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -746,7 +746,7 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
 	 */
 	WRITE_ONCE(slot->gmem.file, file);
 	slot->gmem.pgoff = start;
-	if (kvm_gmem_supports_mmap(inode))
+	if (gmem_in_place_conversion || kvm_gmem_supports_mmap(inode))
 		slot->flags |= KVM_MEMSLOT_GMEM_ONLY;
 
 	xa_store_range(&f->bindings, start, end - 1, slot, GFP_KERNEL);

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 12/45] KVM: guest_memfd: Always fault from guest_memfd if in-place conversion is enabled

[Fuad Tabba]

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Ackerley Tng <ackerleytng@google.com>
>
> If a guest_memfd memslot is created but the guest_memfd does not have the
> GUEST_MEMFD_FLAG_MMAP set, KVM still fulfils guest faults by looking up the
> memslot's userspace_addr.
>
> Set KVM_MEMSLOT_GMEM_ONLY if in-place conversion is enabled so that the
> guest_memfd's memory will be used for both shared and private memory. With
> in-place conversion, guest_memfd will be the only backing memory for the
> memslot.
>
> No validation is performed to require userspace_addr to be a mapping from
> the associated guest_memfd because even after validation, userspace is free
> to remap something else at the provided userspace_addr.
>
> userspace_addr will still be used by functions like kvm_read_guest(), and
> if userspace_addr does not match up with the corresponding memory in the
> memslot's guest_memfd (whether userspace_addr points to the wrong offset or
> some non-guest_memfd memory, etc), that is a user error.
>
> Requiring both shared and private memory to come from the only associated
> guest_memfd simplifies invalidation in stage 2 page tables. On a PUNCH_HOLE
> operation on a guest_memfd, the invalidation is now guaranteed to be
> invalidating only memory mapped from the given guest_memfd.
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

Cheers,
/fuad


> ---
>  Documentation/virt/kvm/api.rst | 22 ++++++++++++++--------
>  virt/kvm/guest_memfd.c         |  2 +-
>  2 files changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 90a29424c54c8..668886f50024d 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6381,10 +6381,16 @@ mapping for userspace_addr is not required to be valid/populated at the time of
>  KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated
>  on-demand.
>
> -When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes
> -userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the
> -sole authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD`
> -to find out more about the creation-time shared/private status.
> +When mapping a gfn into the guest, guest faults are always serviced from
> +guest_memfd regardless of whether memory is shared or private.  KVM determines
> +shared vs. private based on the state in guest_memfd, which is the sole
> +authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD` to
> +find out more about the creation-time shared/private status.
> +
> +userspace_addr is expected to be the mmap()-ed address corresponding to the
> +right offset within the guest_memfd. Any mismatch between userspace_addr and
> +guest_memfd is not validated and is a user error. userspace_addr is only used
> +for host-side guest accesses such as kvm_read_guest().
>
>  If in-place conversion is disabled, KVM selects shared vs. private, i.e consumes
>  userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE
> @@ -6490,10 +6496,10 @@ specified via KVM_CREATE_GUEST_MEMFD.  Currently defined flags:
>                                 page tables. Private memory cannot.
>    ============================ ================================================
>
> -When the KVM MMU performs a PFN lookup to service a guest fault and the backing
> -guest_memfd has the GUEST_MEMFD_FLAG_MMAP set, then the fault will always be
> -consumed from guest_memfd, regardless of whether it is a shared or a private
> -fault.
> +When the KVM MMU performs a PFN lookup to service a guest fault, the fault will
> +always be consumed from guest_memfd, regardless of whether it is a shared or a
> +private fault (unless in-place conversion is disabled and the backing
> +guest_memfd does not have the GUEST_MEMFD_FLAG_MMAP flag set).
>
>  See KVM_SET_USER_MEMORY_REGION2 for additional details.
>
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 0afe1468d2d9d..e41802944756b 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -746,7 +746,7 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
>          */
>         WRITE_ONCE(slot->gmem.file, file);
>         slot->gmem.pgoff = start;
> -       if (kvm_gmem_supports_mmap(inode))
> +       if (gmem_in_place_conversion || kvm_gmem_supports_mmap(inode))
>                 slot->flags |= KVM_MEMSLOT_GMEM_ONLY;
>
>         xa_store_range(&f->bindings, start, end - 1, slot, GFP_KERNEL);
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

Re: [PATCH v12 12/45] KVM: guest_memfd: Always fault from guest_memfd if in-place conversion is enabled

[Yan Zhao]

On Sun, Aug 30, 2026 at 05:25:13PM -0700, Ackerley Tng via B4 Relay wrote:
> From: Ackerley Tng <ackerleytng@google.com>
> 
> If a guest_memfd memslot is created but the guest_memfd does not have the
> GUEST_MEMFD_FLAG_MMAP set, KVM still fulfils guest faults by looking up the
> memslot's userspace_addr.
> 
> Set KVM_MEMSLOT_GMEM_ONLY if in-place conversion is enabled so that the
> guest_memfd's memory will be used for both shared and private memory. With
> in-place conversion, guest_memfd will be the only backing memory for the
> memslot.
> 
> No validation is performed to require userspace_addr to be a mapping from
> the associated guest_memfd because even after validation, userspace is free
> to remap something else at the provided userspace_addr.
> 
> userspace_addr will still be used by functions like kvm_read_guest(), and
> if userspace_addr does not match up with the corresponding memory in the
> memslot's guest_memfd (whether userspace_addr points to the wrong offset or
> some non-guest_memfd memory, etc), that is a user error.
> 
> Requiring both shared and private memory to come from the only associated
> guest_memfd simplifies invalidation in stage 2 page tables. On a PUNCH_HOLE
> operation on a guest_memfd, the invalidation is now guaranteed to be
> invalidating only memory mapped from the given guest_memfd.
> 
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> ---
>  Documentation/virt/kvm/api.rst | 22 ++++++++++++++--------
>  virt/kvm/guest_memfd.c         |  2 +-
>  2 files changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 90a29424c54c8..668886f50024d 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6381,10 +6381,16 @@ mapping for userspace_addr is not required to be valid/populated at the time of
>  KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated
>  on-demand.
>  
> -When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes
> -userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the
> -sole authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD`
> -to find out more about the creation-time shared/private status.
> +When mapping a gfn into the guest, guest faults are always serviced from
> +guest_memfd regardless of whether memory is shared or private.  KVM determines
> +shared vs. private based on the state in guest_memfd, which is the sole
> +authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD` to
> +find out more about the creation-time shared/private status.
> +
> +userspace_addr is expected to be the mmap()-ed address corresponding to the
> +right offset within the guest_memfd. Any mismatch between userspace_addr and
> +guest_memfd is not validated and is a user error. userspace_addr is only used
> +for host-side guest accesses such as kvm_read_guest().
>  
>  If in-place conversion is disabled, KVM selects shared vs. private, i.e consumes
>  userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE
> @@ -6490,10 +6496,10 @@ specified via KVM_CREATE_GUEST_MEMFD.  Currently defined flags:
>                                 page tables. Private memory cannot.
>    ============================ ================================================
>  
> -When the KVM MMU performs a PFN lookup to service a guest fault and the backing
> -guest_memfd has the GUEST_MEMFD_FLAG_MMAP set, then the fault will always be
> -consumed from guest_memfd, regardless of whether it is a shared or a private
> -fault.
> +When the KVM MMU performs a PFN lookup to service a guest fault, the fault will
> +always be consumed from guest_memfd, regardless of whether it is a shared or a
> +private fault (unless in-place conversion is disabled and the backing
> +guest_memfd does not have the GUEST_MEMFD_FLAG_MMAP flag set).
>  
>  See KVM_SET_USER_MEMORY_REGION2 for additional details.
>  
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 0afe1468d2d9d..e41802944756b 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -746,7 +746,7 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
>  	 */
>  	WRITE_ONCE(slot->gmem.file, file);
>  	slot->gmem.pgoff = start;
> -	if (kvm_gmem_supports_mmap(inode))
> +	if (gmem_in_place_conversion || kvm_gmem_supports_mmap(inode))
>  		slot->flags |= KVM_MEMSLOT_GMEM_ONLY;
I like this change, which actually enforces in-place conversion -- when
gmem_in_place_conversion is true, if userspace sets slot->userspace_addr to a
different backend, the host and guest will no longer be able to access the same
backend.

However, since gmem_in_place_conversion is globally and statically specified, it
essentially disables the coexistence of VMs using out-of-place conversions when
gmem_in_place_conversion is true. Previously, VMs using out-of-place conversions
could still boot successfully as long as they switched to using per-gmem memory
attributes. Is this change intended?

On a separate note, is kvm_gmem_supports_mmap() still a necessary requirement
for setting KVM_MEMSLOT_GMEM_ONLY? When gmem_in_place_conversion is false, if
userspace mmap()s the gmem but sets slot->userspace_addr to a different backend,
should the KVM_MEMSLOT_GMEM_ONLY flag still be set?

>  
>  	xa_store_range(&f->bindings, start, end - 1, slot, GFP_KERNEL);
> 
> -- 
> 2.55.0.897.gb25b4bd76c-goog
> 
> 

Re: [PATCH v12 12/45] KVM: guest_memfd: Always fault from guest_memfd if in-place conversion is enabled

[Binbin Wu]

On 8/31/2026 8:25 AM, Ackerley Tng via B4 Relay wrote:
> From: Ackerley Tng <ackerleytng@google.com>
> 
> If a guest_memfd memslot is created but the guest_memfd does not have the
> GUEST_MEMFD_FLAG_MMAP set, KVM still fulfils guest faults by looking up the
> memslot's userspace_addr.
> 
> Set KVM_MEMSLOT_GMEM_ONLY if in-place conversion is enabled so that the
> guest_memfd's memory will be used for both shared and private memory. With
> in-place conversion, guest_memfd will be the only backing memory for the
> memslot.
> 
> No validation is performed to require userspace_addr to be a mapping from
> the associated guest_memfd because even after validation, userspace is free
> to remap something else at the provided userspace_addr.
> 
> userspace_addr will still be used by functions like kvm_read_guest(), and
> if userspace_addr does not match up with the corresponding memory in the
> memslot's guest_memfd (whether userspace_addr points to the wrong offset or
> some non-guest_memfd memory, etc), that is a user error.
> 
> Requiring both shared and private memory to come from the only associated
> guest_memfd simplifies invalidation in stage 2 page tables. On a PUNCH_HOLE
> operation on a guest_memfd, the invalidation is now guaranteed to be
> invalidating only memory mapped from the given guest_memfd.
> 
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>

[PATCH v12 13/45] KVM: guest_memfd: Pass mapping type filter to invalidation helper

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Accept the mapping type filter as a parameter in the invalidation start
helper instead of querying it internally. This allows callers to specify
which mappings (shared, private, or both) should be invalidated.

In the next patch, the conversion process will use this new parameter to
invalidate mappings only when they're different from the target state of
the conversion, i.e. invalidate only shared mappings on a shared to private
conversion and not both.

No functional change intended.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 virt/kvm/guest_memfd.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index e41802944756b..e19de803149c2 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -192,13 +192,13 @@ static void __kvm_gmem_invalidate_start(struct gmem_file *f, pgoff_t start,
 }
 
 static void kvm_gmem_invalidate_start(struct inode *inode, pgoff_t start,
-				      pgoff_t end)
+				      pgoff_t end,
+				      enum kvm_gfn_range_filter filter)
 {
-	enum kvm_gfn_range_filter attr_filter = kvm_gmem_get_all_gfns_filter(inode);
 	struct gmem_file *f;
 
 	kvm_gmem_for_each_file(f, inode)
-		__kvm_gmem_invalidate_start(f, start, end, attr_filter);
+		__kvm_gmem_invalidate_start(f, start, end, filter);
 }
 
 static void __kvm_gmem_invalidate_end(struct gmem_file *f, pgoff_t start,
@@ -224,6 +224,7 @@ static void kvm_gmem_invalidate_end(struct inode *inode, pgoff_t start,
 
 static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 {
+	enum kvm_gfn_range_filter filter = kvm_gmem_get_all_gfns_filter(inode);
 	pgoff_t start = offset >> PAGE_SHIFT;
 	pgoff_t end = (offset + len) >> PAGE_SHIFT;
 
@@ -233,7 +234,7 @@ static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 	 */
 	filemap_invalidate_lock(inode->i_mapping);
 
-	kvm_gmem_invalidate_start(inode, start, end);
+	kvm_gmem_invalidate_start(inode, start, end, filter);
 
 	truncate_inode_pages_range(inode->i_mapping, offset, offset + len - 1);
 
@@ -522,6 +523,8 @@ static int kvm_gmem_migrate_folio(struct address_space *mapping,
 
 static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *folio)
 {
+	struct inode *inode = mapping->host;
+	enum kvm_gfn_range_filter filter;
 	pgoff_t start, end;
 
 	filemap_invalidate_lock_shared(mapping);
@@ -529,7 +532,8 @@ static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *fol
 	start = folio->index;
 	end = start + folio_nr_pages(folio);
 
-	kvm_gmem_invalidate_start(mapping->host, start, end);
+	filter = kvm_gmem_get_all_gfns_filter(inode);
+	kvm_gmem_invalidate_start(inode, start, end, filter);
 
 	/*
 	 * Do not truncate the range, what action is taken in response to the

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 13/45] KVM: guest_memfd: Pass mapping type filter to invalidation helper

[Fuad Tabba]

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Ackerley Tng <ackerleytng@google.com>
>
> Accept the mapping type filter as a parameter in the invalidation start
> helper instead of querying it internally. This allows callers to specify
> which mappings (shared, private, or both) should be invalidated.
>
> In the next patch, the conversion process will use this new parameter to
> invalidate mappings only when they're different from the target state of
> the conversion, i.e. invalidate only shared mappings on a shared to private
> conversion and not both.
>
> No functional change intended.
>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

Cheers,
/fuad


> ---
>  virt/kvm/guest_memfd.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index e41802944756b..e19de803149c2 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -192,13 +192,13 @@ static void __kvm_gmem_invalidate_start(struct gmem_file *f, pgoff_t start,
>  }
>
>  static void kvm_gmem_invalidate_start(struct inode *inode, pgoff_t start,
> -                                     pgoff_t end)
> +                                     pgoff_t end,
> +                                     enum kvm_gfn_range_filter filter)
>  {
> -       enum kvm_gfn_range_filter attr_filter = kvm_gmem_get_all_gfns_filter(inode);
>         struct gmem_file *f;
>
>         kvm_gmem_for_each_file(f, inode)
> -               __kvm_gmem_invalidate_start(f, start, end, attr_filter);
> +               __kvm_gmem_invalidate_start(f, start, end, filter);
>  }
>
>  static void __kvm_gmem_invalidate_end(struct gmem_file *f, pgoff_t start,
> @@ -224,6 +224,7 @@ static void kvm_gmem_invalidate_end(struct inode *inode, pgoff_t start,
>
>  static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
>  {
> +       enum kvm_gfn_range_filter filter = kvm_gmem_get_all_gfns_filter(inode);
>         pgoff_t start = offset >> PAGE_SHIFT;
>         pgoff_t end = (offset + len) >> PAGE_SHIFT;
>
> @@ -233,7 +234,7 @@ static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
>          */
>         filemap_invalidate_lock(inode->i_mapping);
>
> -       kvm_gmem_invalidate_start(inode, start, end);
> +       kvm_gmem_invalidate_start(inode, start, end, filter);
>
>         truncate_inode_pages_range(inode->i_mapping, offset, offset + len - 1);
>
> @@ -522,6 +523,8 @@ static int kvm_gmem_migrate_folio(struct address_space *mapping,
>
>  static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *folio)
>  {
> +       struct inode *inode = mapping->host;
> +       enum kvm_gfn_range_filter filter;
>         pgoff_t start, end;
>
>         filemap_invalidate_lock_shared(mapping);
> @@ -529,7 +532,8 @@ static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *fol
>         start = folio->index;
>         end = start + folio_nr_pages(folio);
>
> -       kvm_gmem_invalidate_start(mapping->host, start, end);
> +       filter = kvm_gmem_get_all_gfns_filter(inode);
> +       kvm_gmem_invalidate_start(inode, start, end, filter);
>
>         /*
>          * Do not truncate the range, what action is taken in response to the
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

Re: [PATCH v12 13/45] KVM: guest_memfd: Pass mapping type filter to invalidation helper

[Binbin Wu]

On 8/31/2026 8:25 AM, Ackerley Tng via B4 Relay wrote:
> From: Ackerley Tng <ackerleytng@google.com>
> 
> Accept the mapping type filter as a parameter in the invalidation start
> helper instead of querying it internally. This allows callers to specify
> which mappings (shared, private, or both) should be invalidated.
> 
> In the next patch, the conversion process will use this new parameter to
> invalidate mappings only when they're different from the target state of
> the conversion, i.e. invalidate only shared mappings on a shared to private
> conversion and not both.
> 
> No functional change intended.
> 
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>

[PATCH v12 14/45] KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Add a new ioctl (and matching struct), KVM_SET_MEMORY_ATTRIBUTES2, using
the same base ioctl number (0xd2), but with R/W semantics for the kernel
instead of just read semantics.  "Officially" documenting that KVM writes
to the payload will allow KVM to support partial/incremental conversions,
instead of all-or-nothing updates (which requires complex unwinding), by
recording the failing offset if an error occurs.

Opportunistically add a new struct as well, even though KVM could squeeze
the error offset into "struct kvm_memory_attributes", as there's no cost to
doing so in practice.  Pad the struct with a pile of extra space to try and
avoid ending up with "struct kvm_memory_attributes3" in the future.  Use
the same layout for the fields common to version 1 of the struct, e.g. to
ease upgrading userspace, and to provide flexibility if KVM ever adds
support for KVM_SET_MEMORY_ATTRIBUTES2 at VM scope.

Introduce KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES to advertise the
availability of the KVM_SET_MEMORY_ATTRIBUTES2 ioctl.

Update the KVM API documentation to define the new ioctl and its behavior,
and add the necessary UAPI definitions and capability checks.

The process of setting memory attributes has a clear point of no return
because, for CoCo VMs, zapping stage 2 page tables is a destructive
operation. Unlike regular VMs, where re-faulting pages into the stage 2
page tables merely incurs a performance penalty, CoCo guests must
(re-):accept pages after every fault. To preserve CoCo security guarantees,
guests will not accept pages they did not explicitly request faults
for. Consequently, during memory conversions, any operation that could
cause the process to abort must be completed before the stage 2 page tables
are zapped.

Zap only the ranges that are not already in the requested state to avoid
inadvertently destroying (CoCo) data. ARM CCA guests will try to mark the
entire DRAM as private at boot. If there are no shared pages at all, the
to-private conversion can be skipped, but the existence of a single shared
page would require the conversion process to proceed, and if it proceeds,
zapping both shared and private pages would destroy data and break the
guest.

Co-developed-by: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Suggested-by: Michael Roth <michael.roth@amd.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 Documentation/virt/kvm/api.rst |  71 +++++++++++++++++++++++-
 include/uapi/linux/kvm.h       |  15 ++++++
 virt/kvm/guest_memfd.c         | 119 +++++++++++++++++++++++++++++++++++++++++
 virt/kvm/kvm_main.c            |  23 +++++---
 4 files changed, 219 insertions(+), 9 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 668886f50024d..4dbf452f6e809 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -117,7 +117,7 @@ description:
       x86 includes both i386 and x86_64.
 
   Type:
-      system, vm, or vcpu.
+      system, vm, vcpu or guest_memfd.
 
   Parameters:
       what parameters are accepted by the ioctl.
@@ -6385,7 +6385,9 @@ When mapping a gfn into the guest, guest faults are always serviced from
 guest_memfd regardless of whether memory is shared or private.  KVM determines
 shared vs. private based on the state in guest_memfd, which is the sole
 authority on private vs. shared memory.  See :ref:`KVM_CREATE_GUEST_MEMFD` to
-find out more about the creation-time shared/private status.
+find out more about the creation-time shared/private status.  Userspace can
+control whether memory is shared/private by toggling
+KVM_MEMORY_ATTRIBUTE_PRIVATE via :ref:`KVM_SET_MEMORY_ATTRIBUTES2` as needed.
 
 userspace_addr is expected to be the mmap()-ed address corresponding to the
 right offset within the guest_memfd. Any mismatch between userspace_addr and
@@ -6404,6 +6406,8 @@ S390:
 Returns -EINVAL if the VM has the KVM_VM_S390_UCONTROL flag set.
 Returns -EINVAL if called on a protected VM.
 
+.. _KVM_SET_MEMORY_ATTRIBUTES:
+
 4.141 KVM_SET_MEMORY_ATTRIBUTES
 -------------------------------
 
@@ -6440,6 +6444,8 @@ the state of a gfn/page as needed.
 
 The "flags" field is reserved for future extensions and must be '0'.
 
+See also: :ref:`KVM_SET_MEMORY_ATTRIBUTES2`.
+
 .. _KVM_CREATE_GUEST_MEMFD:
 
 4.142 KVM_CREATE_GUEST_MEMFD
@@ -6599,6 +6605,67 @@ KVM_S390_KEYOP_SSKE
   Sets the storage key for the guest address ``guest_addr`` to the key
   specified in ``key``, returning the previous value in ``key``.
 
+.. _KVM_SET_MEMORY_ATTRIBUTES2:
+
+4.145 KVM_SET_MEMORY_ATTRIBUTES2
+---------------------------------
+
+:Capability: KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES
+:Architectures: all
+:Type: guest_memfd ioctl
+:Parameters: struct kvm_memory_attributes2 (in)
+:Returns: 0 on success, <0 on error
+
+Errors:
+
+  ========== ===============================================================
+  EINVAL     The specified `offset` or `size` was invalid (e.g. not
+             page aligned, causes an overflow, or size is zero).
+  EFAULT     The parameter address was invalid.
+  ENOMEM     Ran out of memory trying to track private/shared state
+  ========== ===============================================================
+
+KVM_SET_MEMORY_ATTRIBUTES2 is an extension to
+KVM_SET_MEMORY_ATTRIBUTES that supports returning (writing) values to
+userspace.  The original (pre-extension) fields are shared with
+KVM_SET_MEMORY_ATTRIBUTES identically.
+
+Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
+
+::
+
+  struct kvm_memory_attributes2 {
+	union {
+		__u64 address;
+		__u64 offset;
+	};
+	__u64 size;
+	__u64 attributes;
+	__u64 flags;
+	__u64 reserved[12];
+  };
+
+  #define KVM_MEMORY_ATTRIBUTE_PRIVATE           (1ULL << 3)
+
+Set attributes for a range of offsets within a guest_memfd to
+KVM_MEMORY_ATTRIBUTE_PRIVATE to limit the specified guest_memfd backed
+memory range for guest use. Even if KVM_CAP_GUEST_MEMFD_MMAP is
+supported, after a successful call to set
+KVM_MEMORY_ATTRIBUTE_PRIVATE, the requested range will not be mappable
+into host userspace and will only be mappable by the guest.
+
+To allow the range to be mappable into host userspace again, call
+KVM_SET_MEMORY_ATTRIBUTES2 on the guest_memfd again with
+KVM_MEMORY_ATTRIBUTE_PRIVATE unset.
+
+KVM does not directly manipulate the memory contents of pages during
+attribute updates. However, the process of setting these attributes,
+which includes operations such as unmapping pages from the host or
+stage-2 page tables, may result in side effects on memory contents
+that vary across different trusted firmware implementations.
+
+See also: :ref:`KVM_SET_MEMORY_ATTRIBUTES`.
+
 4.145 KVM_PPC_GET_COMPAT_CAPS
 -----------------------------
 :Capability: KVM_CAP_PPC_COMPAT_CAPS
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ac2d77d149635..ac371a50041c9 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -999,6 +999,7 @@ struct kvm_enable_cap {
 #define KVM_CAP_S390_HPAGE_2G 249
 #define KVM_CAP_PPC_COMPAT_CAPS 250
 #define KVM_CAP_ARM_PMU_V3_STRICT 251
+#define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 252
 
 struct kvm_irq_routing_irqchip {
 	__u32 irqchip;
@@ -1653,6 +1654,20 @@ struct kvm_memory_attributes {
 	__u64 flags;
 };
 
+/* Available with KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES */
+#define KVM_SET_MEMORY_ATTRIBUTES2              _IOWR(KVMIO,  0xd2, struct kvm_memory_attributes2)
+
+struct kvm_memory_attributes2 {
+	union {
+		__u64 address;
+		__u64 offset;
+	};
+	__u64 size;
+	__u64 attributes;
+	__u64 flags;
+	__u64 reserved[12];
+};
+
 #define KVM_MEMORY_ATTRIBUTE_PRIVATE           (1ULL << 3)
 
 #define KVM_CREATE_GUEST_MEMFD	_IOWR(KVMIO,  0xd4, struct kvm_create_guest_memfd)
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index e19de803149c2..803c7cdbbe0f6 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -506,11 +506,130 @@ bool kvm_gmem_is_private_gfn(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_is_private_gfn);
 
+/*
+ * Preallocate memory for attributes to be stored on a maple tree, pointed to
+ * by mas.  Adjacent ranges with attributes identical to the new attributes
+ * will be merged.  Also sets mas's bounds up for storing attributes.
+ *
+ * This maintains the invariant that ranges with the same attributes will
+ * always be merged.
+ */
+static int kvm_gmem_mas_preallocate(struct ma_state *mas, u64 attributes,
+				    pgoff_t start, size_t nr_pages)
+{
+	pgoff_t end = start + nr_pages;
+	pgoff_t last = end - 1;
+	void *entry;
+
+	/* Try extending range. entry is NULL on overflow/wrap-around. */
+	mas_set(mas, end);
+	entry = mas_find(mas, end);
+	if (entry && xa_to_value(entry) == attributes)
+		last = mas->last;
+
+	if (start > 0) {
+		mas_set(mas, start - 1);
+		entry = mas_find(mas, start - 1);
+		if (entry && xa_to_value(entry) == attributes)
+			start = mas->index;
+	}
+
+	mas_set_range(mas, start, last);
+	return mas_preallocate(mas, xa_mk_value(attributes), GFP_KERNEL);
+}
+
+static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
+				     size_t nr_pages, uint64_t attrs)
+{
+	bool to_private = attrs & KVM_MEMORY_ATTRIBUTE_PRIVATE;
+	struct address_space *mapping = inode->i_mapping;
+	struct gmem_inode *gi = GMEM_I(inode);
+	enum kvm_gfn_range_filter filter;
+	pgoff_t end = start + nr_pages;
+	struct maple_tree *mt;
+	struct ma_state mas;
+	int r;
+
+	mt = &gi->attributes;
+
+	filemap_invalidate_lock(mapping);
+
+	mas_init(&mas, mt, start);
+	r = kvm_gmem_mas_preallocate(&mas, attrs, start, nr_pages);
+	if (r)
+		goto out;
+
+	/*
+	 * From this point on guest_memfd has performed necessary
+	 * checks and can proceed to do guest-breaking changes.
+	 */
+
+	filter = to_private ? KVM_FILTER_SHARED : KVM_FILTER_PRIVATE;
+	kvm_gmem_invalidate_start(inode, start, end, filter);
+	mas_store_prealloc(&mas, xa_mk_value(attrs));
+	kvm_gmem_invalidate_end(inode, start, end);
+out:
+	filemap_invalidate_unlock(mapping);
+	return r;
+}
+
+static long kvm_gmem_set_attributes(struct file *file, void __user *argp)
+{
+	struct gmem_file *f = file->private_data;
+	struct inode *inode = file_inode(file);
+	struct kvm_memory_attributes2 attrs;
+	size_t nr_pages;
+	pgoff_t index;
+	int i;
+
+	if (copy_from_user(&attrs, argp, sizeof(attrs)))
+		return -EFAULT;
+
+	if (attrs.flags)
+		return -EINVAL;
+	for (i = 0; i < ARRAY_SIZE(attrs.reserved); i++) {
+		if (attrs.reserved[i])
+			return -EINVAL;
+	}
+	if (!kvm_arch_has_private_mem(f->kvm))
+		return -EINVAL;
+	if (attrs.attributes & ~KVM_MEMORY_ATTRIBUTE_PRIVATE)
+		return -EINVAL;
+	if (attrs.size == 0 || attrs.offset + attrs.size < attrs.offset)
+		return -EINVAL;
+	if (!PAGE_ALIGNED(attrs.offset) || !PAGE_ALIGNED(attrs.size))
+		return -EINVAL;
+
+	if (attrs.offset >= i_size_read(inode) ||
+	    attrs.offset + attrs.size > i_size_read(inode))
+		return -EINVAL;
+
+	nr_pages = attrs.size >> PAGE_SHIFT;
+	index = attrs.offset >> PAGE_SHIFT;
+	return __kvm_gmem_set_attributes(inode, index, nr_pages,
+					 attrs.attributes);
+}
+
+static long kvm_gmem_ioctl(struct file *file, unsigned int ioctl,
+			   unsigned long arg)
+{
+	switch (ioctl) {
+	case KVM_SET_MEMORY_ATTRIBUTES2:
+		if (!gmem_in_place_conversion)
+			return -ENOTTY;
+
+		return kvm_gmem_set_attributes(file, (void __user *)arg);
+	default:
+		return -ENOTTY;
+	}
+}
+
 static struct file_operations kvm_gmem_fops = {
 	.mmap		= kvm_gmem_mmap,
 	.open		= generic_file_open,
 	.release	= kvm_gmem_release,
 	.fallocate	= kvm_gmem_fallocate,
+	.unlocked_ioctl	= kvm_gmem_ioctl,
 };
 
 static int kvm_gmem_migrate_folio(struct address_space *mapping,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 46d2e123448c2..1ea8198821917 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2423,18 +2423,22 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 }
 #endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
 
+#ifdef kvm_arch_has_private_mem
+static u64 kvm_supports_private_mem(struct kvm *kvm)
+{
+	return !kvm || kvm_arch_has_private_mem(kvm);
+}
+#else
+#define kvm_supports_private_mem(kvm) false
+#endif
+
 #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 static u64 kvm_supported_vm_mem_attributes(struct kvm *kvm)
 {
-#ifdef kvm_arch_has_private_mem
-	if (gmem_in_place_conversion)
+	if (gmem_in_place_conversion || !kvm_supports_private_mem(kvm))
 		return 0;
 
-	if (!kvm || kvm_arch_has_private_mem(kvm))
-		return KVM_MEMORY_ATTRIBUTE_PRIVATE;
-#endif
-
-	return 0;
+	return KVM_MEMORY_ATTRIBUTE_PRIVATE;
 }
 
 /*
@@ -4976,6 +4980,11 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
 		return 1;
 	case KVM_CAP_GUEST_MEMFD_FLAGS:
 		return kvm_gmem_get_supported_flags(kvm);
+	case KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES:
+		if (!gmem_in_place_conversion || !kvm_supports_private_mem(kvm))
+			return 0;
+
+		return KVM_MEMORY_ATTRIBUTE_PRIVATE;
 #endif
 	default:
 		break;

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 14/45] KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2

[Fuad Tabba]

Hi Ackerley,

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Ackerley Tng <ackerleytng@google.com>
...
> +.. _KVM_SET_MEMORY_ATTRIBUTES2:
> +
> +4.145 KVM_SET_MEMORY_ATTRIBUTES2

This section number collides with the existing 4.145 (KVM_PPC_GET_COMPAT_CAPS)
below, so api.rst ends up with two 4.145 sections. One of them needs
renumbering.

...
>  4.145 KVM_PPC_GET_COMPAT_CAPS

Cheers,
/fuad

[PATCH v12 15/45] KVM: guest_memfd: Ensure pages are not in use before conversion

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

When converting memory to private in guest_memfd, it is necessary to ensure
that the pages are not currently being accessed by any other part of the
kernel or userspace to avoid any current user writing to guest private
memory.

guest_memfd checks for any outstanding references to determine whether a
page is still in use. The only expected references after unmapping the
range requested for conversion are those that are held by guest_memfd
itself.

Update the kvm_memory_attributes2 structure to include an error_offset
field. This allows KVM to report the exact offset where a conversion
failed. If the safety check fails, return -EAGAIN and copy the error_offset
back to userspace so that it can potentially retry the operation or handle
the failure gracefully.

Update documentation to document the error_offset field and the possible
-EAGAIN error.

Suggested-by: David Hildenbrand <david@kernel.org>
Co-developed-by: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 Documentation/virt/kvm/api.rst | 19 +++++++++--
 include/uapi/linux/kvm.h       |  3 +-
 virt/kvm/guest_memfd.c         | 77 +++++++++++++++++++++++++++++++++++++++---
 3 files changed, 91 insertions(+), 8 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 4dbf452f6e809..25cb15970f1ae 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6613,7 +6613,7 @@ KVM_S390_KEYOP_SSKE
 :Capability: KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES
 :Architectures: all
 :Type: guest_memfd ioctl
-:Parameters: struct kvm_memory_attributes2 (in)
+:Parameters: struct kvm_memory_attributes2 (in/out)
 :Returns: 0 on success, <0 on error
 
 Errors:
@@ -6622,6 +6622,8 @@ Errors:
   EINVAL     The specified `offset` or `size` was invalid (e.g. not
              page aligned, causes an overflow, or size is zero).
   EFAULT     The parameter address was invalid.
+  EAGAIN     Some page within requested range had unexpected refcounts. The
+             offset of the page will be returned in `error_offset`.
   ENOMEM     Ran out of memory trying to track private/shared state
   ========== ===============================================================
 
@@ -6635,6 +6637,7 @@ Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
 ::
 
   struct kvm_memory_attributes2 {
+	/* in */
 	union {
 		__u64 address;
 		__u64 offset;
@@ -6642,7 +6645,9 @@ Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
 	__u64 size;
 	__u64 attributes;
 	__u64 flags;
-	__u64 reserved[12];
+	/* out */
+	__u64 error_offset;
+	__u64 reserved[11];
   };
 
   #define KVM_MEMORY_ATTRIBUTE_PRIVATE           (1ULL << 3)
@@ -6664,6 +6669,16 @@ which includes operations such as unmapping pages from the host or
 stage-2 page tables, may result in side effects on memory contents
 that vary across different trusted firmware implementations.
 
+If this ioctl returns -EAGAIN, the offset of the page with unexpected
+refcounts will be returned in ``error_offset``. This can occur if
+there are transient refcounts on the pages, taken by other parts of
+the kernel.
+
+Userspace is expected to figure out how to remove all known refcounts
+on the shared pages, such as refcounts taken by get_user_pages(), and
+try the ioctl again. A possible source of these long term refcounts is
+if the guest_memfd memory was pinned in IOMMU page tables.
+
 See also: :ref:`KVM_SET_MEMORY_ATTRIBUTES`.
 
 4.145 KVM_PPC_GET_COMPAT_CAPS
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ac371a50041c9..8dff2fc1972e9 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1665,7 +1665,8 @@ struct kvm_memory_attributes2 {
 	__u64 size;
 	__u64 attributes;
 	__u64 flags;
-	__u64 reserved[12];
+	__u64 error_offset;
+	__u64 reserved[11];
 };
 
 #define KVM_MEMORY_ATTRIBUTE_PRIVATE           (1ULL << 3)
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 803c7cdbbe0f6..fe02c47c85fb5 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -538,8 +538,46 @@ static int kvm_gmem_mas_preallocate(struct ma_state *mas, u64 attributes,
 	return mas_preallocate(mas, xa_mk_value(attributes), GFP_KERNEL);
 }
 
+static bool kvm_gmem_has_outstanding_references(struct inode *inode,
+						pgoff_t start, size_t nr_pages,
+						pgoff_t *err_index)
+{
+	struct address_space *mapping = inode->i_mapping;
+	pgoff_t last = start + nr_pages - 1;
+	bool has_outstanding = false;
+	struct folio_batch fbatch;
+	pgoff_t next;
+	int i;
+
+	folio_batch_init(&fbatch);
+
+	next = start;
+	while (has_outstanding && filemap_get_folios(mapping, &next, last, &fbatch)) {
+		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
+			struct folio *folio = fbatch.folios[i];
+
+			/*
+			 * Outstanding references are anything other than those
+			 * from the page cache, plus 1 temporary reference held
+			 * by filemap_get_folios() in the folio batch.
+			 */
+			if (folio_ref_count(folio) != folio_nr_pages(folio) + 1) {
+				has_outstanding = true;
+				*err_index = max(start, folio->index);
+				break;
+			}
+		}
+
+		folio_batch_release(&fbatch);
+		cond_resched();
+	}
+
+	return has_outstanding;
+}
+
 static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
-				     size_t nr_pages, uint64_t attrs)
+				     size_t nr_pages, uint64_t attrs,
+				     pgoff_t *err_index)
 {
 	bool to_private = attrs & KVM_MEMORY_ATTRIBUTE_PRIVATE;
 	struct address_space *mapping = inode->i_mapping;
@@ -556,8 +594,28 @@ static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
 
 	mas_init(&mas, mt, start);
 	r = kvm_gmem_mas_preallocate(&mas, attrs, start, nr_pages);
-	if (r)
+	if (r) {
+		*err_index = start;
 		goto out;
+	}
+
+	if (to_private) {
+		/*
+		 * Forcefully unmap the pages from all userspace page tables,
+		 * and then verify there are no outstanding references, e.g.
+		 * acquired via GUP or similar.  Tell userspace to try again if
+		 * there are outstanding references and hope that whatever has
+		 * pinned the page will put its reference "soon".
+		 */
+		unmap_mapping_pages(mapping, start, nr_pages, false);
+
+		if (kvm_gmem_has_outstanding_references(inode, start, nr_pages,
+							err_index)) {
+			mas_destroy(&mas);
+			r = -EAGAIN;
+			goto out;
+		}
+	}
 
 	/*
 	 * From this point on guest_memfd has performed necessary
@@ -578,9 +636,10 @@ static long kvm_gmem_set_attributes(struct file *file, void __user *argp)
 	struct gmem_file *f = file->private_data;
 	struct inode *inode = file_inode(file);
 	struct kvm_memory_attributes2 attrs;
+	pgoff_t err_index;
 	size_t nr_pages;
 	pgoff_t index;
-	int i;
+	int i, r;
 
 	if (copy_from_user(&attrs, argp, sizeof(attrs)))
 		return -EFAULT;
@@ -606,8 +665,16 @@ static long kvm_gmem_set_attributes(struct file *file, void __user *argp)
 
 	nr_pages = attrs.size >> PAGE_SHIFT;
 	index = attrs.offset >> PAGE_SHIFT;
-	return __kvm_gmem_set_attributes(inode, index, nr_pages,
-					 attrs.attributes);
+	r = __kvm_gmem_set_attributes(inode, index, nr_pages, attrs.attributes,
+				      &err_index);
+	if (r) {
+		attrs.error_offset = ((uint64_t)err_index) << PAGE_SHIFT;
+
+		if (copy_to_user(argp, &attrs, sizeof(attrs)))
+			return -EFAULT;
+	}
+
+	return r;
 }
 
 static long kvm_gmem_ioctl(struct file *file, unsigned int ioctl,

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 15/45] KVM: guest_memfd: Ensure pages are not in use before conversion

[Fuad Tabba]

Hi Ackerley,

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Ackerley Tng <ackerleytng@google.com>
>
> When converting memory to private in guest_memfd, it is necessary to ensure
> that the pages are not currently being accessed by any other part of the
> kernel or userspace to avoid any current user writing to guest private
> memory.
>
> guest_memfd checks for any outstanding references to determine whether a
> page is still in use. The only expected references after unmapping the
> range requested for conversion are those that are held by guest_memfd
> itself.
>
> Update the kvm_memory_attributes2 structure to include an error_offset
> field. This allows KVM to report the exact offset where a conversion
> failed. If the safety check fails, return -EAGAIN and copy the error_offset
> back to userspace so that it can potentially retry the operation or handle
> the failure gracefully.
>
> Update documentation to document the error_offset field and the possible
> -EAGAIN error.
>
> Suggested-by: David Hildenbrand <david@kernel.org>
> Co-developed-by: Vishal Annapurve <vannapurve@google.com>
> Signed-off-by: Vishal Annapurve <vannapurve@google.com>
> Reviewed-by: Fuad Tabba <tabba@google.com>
> Tested-by: Shivank Garg <shivankg@amd.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> ---
>  Documentation/virt/kvm/api.rst | 19 +++++++++--
>  include/uapi/linux/kvm.h       |  3 +-
>  virt/kvm/guest_memfd.c         | 77 +++++++++++++++++++++++++++++++++++++++---
>  3 files changed, 91 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 4dbf452f6e809..25cb15970f1ae 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6613,7 +6613,7 @@ KVM_S390_KEYOP_SSKE
>  :Capability: KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES
>  :Architectures: all
>  :Type: guest_memfd ioctl
> -:Parameters: struct kvm_memory_attributes2 (in)
> +:Parameters: struct kvm_memory_attributes2 (in/out)
>  :Returns: 0 on success, <0 on error
>
>  Errors:
> @@ -6622,6 +6622,8 @@ Errors:
>    EINVAL     The specified `offset` or `size` was invalid (e.g. not
>               page aligned, causes an overflow, or size is zero).
>    EFAULT     The parameter address was invalid.
> +  EAGAIN     Some page within requested range had unexpected refcounts. The
> +             offset of the page will be returned in `error_offset`.
>    ENOMEM     Ran out of memory trying to track private/shared state
>    ========== ===============================================================
>
> @@ -6635,6 +6637,7 @@ Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
>  ::
>
>    struct kvm_memory_attributes2 {
> +       /* in */
>         union {
>                 __u64 address;
>                 __u64 offset;
> @@ -6642,7 +6645,9 @@ Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
>         __u64 size;
>         __u64 attributes;
>         __u64 flags;
> -       __u64 reserved[12];
> +       /* out */
> +       __u64 error_offset;
> +       __u64 reserved[11];
>    };
>
>    #define KVM_MEMORY_ATTRIBUTE_PRIVATE           (1ULL << 3)
> @@ -6664,6 +6669,16 @@ which includes operations such as unmapping pages from the host or
>  stage-2 page tables, may result in side effects on memory contents
>  that vary across different trusted firmware implementations.
>
> +If this ioctl returns -EAGAIN, the offset of the page with unexpected
> +refcounts will be returned in ``error_offset``. This can occur if
> +there are transient refcounts on the pages, taken by other parts of
> +the kernel.
> +
> +Userspace is expected to figure out how to remove all known refcounts
> +on the shared pages, such as refcounts taken by get_user_pages(), and
> +try the ioctl again. A possible source of these long term refcounts is
> +if the guest_memfd memory was pinned in IOMMU page tables.
> +
>  See also: :ref:`KVM_SET_MEMORY_ATTRIBUTES`.
>
>  4.145 KVM_PPC_GET_COMPAT_CAPS
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index ac371a50041c9..8dff2fc1972e9 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1665,7 +1665,8 @@ struct kvm_memory_attributes2 {
>         __u64 size;
>         __u64 attributes;
>         __u64 flags;
> -       __u64 reserved[12];
> +       __u64 error_offset;
> +       __u64 reserved[11];
>  };
>
>  #define KVM_MEMORY_ATTRIBUTE_PRIVATE           (1ULL << 3)
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 803c7cdbbe0f6..fe02c47c85fb5 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -538,8 +538,46 @@ static int kvm_gmem_mas_preallocate(struct ma_state *mas, u64 attributes,
>         return mas_preallocate(mas, xa_mk_value(attributes), GFP_KERNEL);
>  }
>
> +static bool kvm_gmem_has_outstanding_references(struct inode *inode,
> +                                               pgoff_t start, size_t nr_pages,
> +                                               pgoff_t *err_index)
> +{
> +       struct address_space *mapping = inode->i_mapping;
> +       pgoff_t last = start + nr_pages - 1;
> +       bool has_outstanding = false;
> +       struct folio_batch fbatch;
> +       pgoff_t next;
> +       int i;
> +
> +       folio_batch_init(&fbatch);
> +
> +       next = start;
> +       while (has_outstanding && filemap_get_folios(mapping, &next, last, &fbatch)) {

has_outstanding starts as false, so the loop never runs and the function
always returns false. The outstanding-reference check is dead at this
patch, so a to-private conversion would not be rejected even when a page
still has an outstanding reference.

It's fixed later in "KVM: guest_memfd: Handle lru_add fbatch refcounts
during conversion safety check", which changes the condition to
!has_outstanding. I think that fix belongs in this patch, so the check
works when it is introduced and the series bisects cleanly.

Missed it on the previous review, but with this fixed it still holds.

Cheers,
/fuad



> +               for (i = 0; i < folio_batch_count(&fbatch); ++i) {
> +                       struct folio *folio = fbatch.folios[i];
> +
> +                       /*
> +                        * Outstanding references are anything other than those
> +                        * from the page cache, plus 1 temporary reference held
> +                        * by filemap_get_folios() in the folio batch.
> +                        */
> +                       if (folio_ref_count(folio) != folio_nr_pages(folio) + 1) {
> +                               has_outstanding = true;
> +                               *err_index = max(start, folio->index);
> +                               break;
> +                       }
> +               }
> +
> +               folio_batch_release(&fbatch);
> +               cond_resched();
> +       }
> +
> +       return has_outstanding;
> +}
> +
>  static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
> -                                    size_t nr_pages, uint64_t attrs)
> +                                    size_t nr_pages, uint64_t attrs,
> +                                    pgoff_t *err_index)
>  {
>         bool to_private = attrs & KVM_MEMORY_ATTRIBUTE_PRIVATE;
>         struct address_space *mapping = inode->i_mapping;
> @@ -556,8 +594,28 @@ static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
>
>         mas_init(&mas, mt, start);
>         r = kvm_gmem_mas_preallocate(&mas, attrs, start, nr_pages);
> -       if (r)
> +       if (r) {
> +               *err_index = start;
>                 goto out;
> +       }
> +
> +       if (to_private) {
> +               /*
> +                * Forcefully unmap the pages from all userspace page tables,
> +                * and then verify there are no outstanding references, e.g.
> +                * acquired via GUP or similar.  Tell userspace to try again if
> +                * there are outstanding references and hope that whatever has
> +                * pinned the page will put its reference "soon".
> +                */
> +               unmap_mapping_pages(mapping, start, nr_pages, false);
> +
> +               if (kvm_gmem_has_outstanding_references(inode, start, nr_pages,
> +                                                       err_index)) {
> +                       mas_destroy(&mas);
> +                       r = -EAGAIN;
> +                       goto out;
> +               }
> +       }
>
>         /*
>          * From this point on guest_memfd has performed necessary
> @@ -578,9 +636,10 @@ static long kvm_gmem_set_attributes(struct file *file, void __user *argp)
>         struct gmem_file *f = file->private_data;
>         struct inode *inode = file_inode(file);
>         struct kvm_memory_attributes2 attrs;
> +       pgoff_t err_index;
>         size_t nr_pages;
>         pgoff_t index;
> -       int i;
> +       int i, r;
>
>         if (copy_from_user(&attrs, argp, sizeof(attrs)))
>                 return -EFAULT;
> @@ -606,8 +665,16 @@ static long kvm_gmem_set_attributes(struct file *file, void __user *argp)
>
>         nr_pages = attrs.size >> PAGE_SHIFT;
>         index = attrs.offset >> PAGE_SHIFT;
> -       return __kvm_gmem_set_attributes(inode, index, nr_pages,
> -                                        attrs.attributes);
> +       r = __kvm_gmem_set_attributes(inode, index, nr_pages, attrs.attributes,
> +                                     &err_index);
> +       if (r) {
> +               attrs.error_offset = ((uint64_t)err_index) << PAGE_SHIFT;
> +
> +               if (copy_to_user(argp, &attrs, sizeof(attrs)))
> +                       return -EFAULT;
> +       }
> +
> +       return r;
>  }
>
>  static long kvm_gmem_ioctl(struct file *file, unsigned int ioctl,
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

Re: [PATCH v12 15/45] KVM: guest_memfd: Ensure pages are not in use before conversion

[Sean Christopherson]

On Tue, Sep 01, 2026, Fuad Tabba wrote:
> > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> > index 803c7cdbbe0f6..fe02c47c85fb5 100644
> > --- a/virt/kvm/guest_memfd.c
> > +++ b/virt/kvm/guest_memfd.c
> > @@ -538,8 +538,46 @@ static int kvm_gmem_mas_preallocate(struct ma_state *mas, u64 attributes,
> >         return mas_preallocate(mas, xa_mk_value(attributes), GFP_KERNEL);
> >  }
> >
> > +static bool kvm_gmem_has_outstanding_references(struct inode *inode,
> > +                                               pgoff_t start, size_t nr_pages,
> > +                                               pgoff_t *err_index)
> > +{
> > +       struct address_space *mapping = inode->i_mapping;
> > +       pgoff_t last = start + nr_pages - 1;
> > +       bool has_outstanding = false;
> > +       struct folio_batch fbatch;
> > +       pgoff_t next;
> > +       int i;
> > +
> > +       folio_batch_init(&fbatch);
> > +
> > +       next = start;
> > +       while (has_outstanding && filemap_get_folios(mapping, &next, last, &fbatch)) {
> 
> has_outstanding starts as false, so the loop never runs and the function
> always returns false. The outstanding-reference check is dead at this
> patch, so a to-private conversion would not be rejected even when a page
> still has an outstanding reference.
> 
> It's fixed later in "KVM: guest_memfd: Handle lru_add fbatch refcounts
> during conversion safety check", which changes the condition to
> !has_outstanding. I think that fix belongs in this patch, so the check
> works when it is introduced and the series bisects cleanly.

Why even bother with has_outstanding?  Avoiding it requires copy+pasting
folio_batch_release(), but it's less code and IMO the end result is a lot easier
to follow:

	struct address_space *mapping = inode->i_mapping;
	pgoff_t last = start + nr_pages - 1;
	struct folio_batch fbatch;
	pgoff_t next;
	int i;

	folio_batch_init(&fbatch);

	next = start;
	while (filemap_get_folios(mapping, &next, last, &fbatch)) {
		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
			struct folio *folio = fbatch.folios[i];

			/*
			 * Outstanding references are anything other than those
			 * from the page cache, plus 1 temporary reference held
			 * by filemap_get_folios() in the folio batch.
			 */
			if (folio_ref_count(folio) != folio_nr_pages(folio) + 1) {
				*err_index = max(start, folio->index);
				folio_batch_release(&fbatch);
				return true;
			}
		}

		folio_batch_release(&fbatch);
		cond_resched();
	}

	return false;

and then we end up with:

	enum lru_cache_drained drained = LRU_CACHE_NOT_DRAINED;
	struct address_space *mapping = inode->i_mapping;
	pgoff_t last = start + nr_pages - 1;
	struct folio_batch fbatch;
	pgoff_t next;
	int i;

	folio_batch_init(&fbatch);

	next = start;
	while (filemap_get_folios(mapping, &next, last, &fbatch)) {
		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
			struct folio *folio = fbatch.folios[i];

			if (__folio_has_outstanding_references(folio, &drained)) {
				*err_index = max(start, folio->index);
				folio_batch_release(&fbatch);
				return true;
			}
		}

		folio_batch_release(&fbatch);
		cond_resched();
	}

	return false;

Re: [PATCH v12 15/45] KVM: guest_memfd: Ensure pages are not in use before conversion

[Sean Christopherson]

On Tue, Sep 01, 2026, Sean Christopherson wrote:
> On Tue, Sep 01, 2026, Fuad Tabba wrote:
> > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> > > index 803c7cdbbe0f6..fe02c47c85fb5 100644
> > > --- a/virt/kvm/guest_memfd.c
> > > +++ b/virt/kvm/guest_memfd.c
> > > @@ -538,8 +538,46 @@ static int kvm_gmem_mas_preallocate(struct ma_state *mas, u64 attributes,
> > >         return mas_preallocate(mas, xa_mk_value(attributes), GFP_KERNEL);
> > >  }
> > >
> > > +static bool kvm_gmem_has_outstanding_references(struct inode *inode,
> > > +                                               pgoff_t start, size_t nr_pages,
> > > +                                               pgoff_t *err_index)
> > > +{
> > > +       struct address_space *mapping = inode->i_mapping;
> > > +       pgoff_t last = start + nr_pages - 1;
> > > +       bool has_outstanding = false;
> > > +       struct folio_batch fbatch;
> > > +       pgoff_t next;
> > > +       int i;
> > > +
> > > +       folio_batch_init(&fbatch);
> > > +
> > > +       next = start;
> > > +       while (has_outstanding && filemap_get_folios(mapping, &next, last, &fbatch)) {
> > 
> > has_outstanding starts as false, so the loop never runs and the function
> > always returns false. The outstanding-reference check is dead at this
> > patch, so a to-private conversion would not be rejected even when a page
> > still has an outstanding reference.
> > 
> > It's fixed later in "KVM: guest_memfd: Handle lru_add fbatch refcounts
> > during conversion safety check", which changes the condition to
> > !has_outstanding. I think that fix belongs in this patch, so the check
> > works when it is introduced and the series bisects cleanly.

Wait, why are there even separate patches for this?  For all intents and purposes,
"Ensure pages are not in use before conversion" introduces a bug and then the bug
is fixed by "Handle lru_add fbatch refcounts during conversion safety check".
Just don't introduce the bug.

I also recommend splitting the export of lru_cache_drain_for_folio() to its own
patch so that it can be more easily Acked by mm/ folks.  If we want to squash it
with the KVM change, then that's trivial to do when applying.

> Why even bother with has_outstanding?  Avoiding it requires copy+pasting
> folio_batch_release(), but it's less code and IMO the end result is a lot easier
> to follow:
> 
> 	struct address_space *mapping = inode->i_mapping;
> 	pgoff_t last = start + nr_pages - 1;
> 	struct folio_batch fbatch;
> 	pgoff_t next;
> 	int i;
> 
> 	folio_batch_init(&fbatch);
> 
> 	next = start;
> 	while (filemap_get_folios(mapping, &next, last, &fbatch)) {
> 		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
> 			struct folio *folio = fbatch.folios[i];
> 
> 			/*
> 			 * Outstanding references are anything other than those
> 			 * from the page cache, plus 1 temporary reference held
> 			 * by filemap_get_folios() in the folio batch.
> 			 */
> 			if (folio_ref_count(folio) != folio_nr_pages(folio) + 1) {
> 				*err_index = max(start, folio->index);
> 				folio_batch_release(&fbatch);
> 				return true;
> 			}
> 		}
> 
> 		folio_batch_release(&fbatch);
> 		cond_resched();
> 	}
> 
> 	return false;
> 
> and then we end up with:
> 
> 	enum lru_cache_drained drained = LRU_CACHE_NOT_DRAINED;
> 	struct address_space *mapping = inode->i_mapping;
> 	pgoff_t last = start + nr_pages - 1;
> 	struct folio_batch fbatch;
> 	pgoff_t next;
> 	int i;
> 
> 	folio_batch_init(&fbatch);
> 
> 	next = start;
> 	while (filemap_get_folios(mapping, &next, last, &fbatch)) {
> 		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
> 			struct folio *folio = fbatch.folios[i];
> 
> 			if (__folio_has_outstanding_references(folio, &drained)) {
> 				*err_index = max(start, folio->index);
> 				folio_batch_release(&fbatch);
> 				return true;
> 			}
> 		}
> 
> 		folio_batch_release(&fbatch);
> 		cond_resched();
> 	}
> 
> 	return false;

[PATCH v12 16/45] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

When doing in-place conversion from PRIVATE to SHARED, immediately inform
arch code of the conversion for all allocated pages/folios, e.g. so that
arch code can put hardware metadata tables in the correct state.  Eagerly
updating the table for to SHARED conversions avoids having to implement
on-demand updates, e.g. when faulting in host userspace mappings.  Skip the
entire flow if the arch doesn't implement conversion callbacks, as getting
folios from the filemap is noticeably expensive, especially when converting
large chunks of memory.

Deliberately don't eagerly update the metadata table on conversions from
SHARED to PRIVATE, because assigning a page to a VM (versus "returning" it
to the host) requires the exact GFN associated with the page, i.e would
require walking the memslot bindings.  And because KVM *must* do on-demand
metadata updates when getting a PFN for KVM-internal usage, as that's the
only time a relevant memslot binding is guaranteed to exist.

Note!  Inform arch code of the conversion within the protection of the
invalidation sequence, to ensure that any existing mappings are dropped
before hardware is updated, and to ensure that new mappings can't be
established until after the conversion is complete.

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 arch/x86/include/asm/kvm-x86-ops.h |  2 +-
 arch/x86/include/asm/kvm_host.h    |  2 +-
 arch/x86/kvm/x86.c                 |  5 +++++
 include/linux/kvm_host.h           |  1 +
 virt/kvm/guest_memfd.c             | 42 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index e213c9ae3e301..67b43c167045b 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -150,7 +150,7 @@ KVM_X86_OP_OPTIONAL(alloc_apic_backing_page)
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
 KVM_X86_OP_OPTIONAL_RET0(gmem_make_private)
 #endif
-#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_RECLAIM
+#if defined(CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT) || defined(CONFIG_HAVE_KVM_ARCH_GMEM_RECLAIM)
 KVM_X86_OP_OPTIONAL(gmem_make_shared)
 #endif
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 744c1f6ff03ed..83e26ce45fb79 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1732,7 +1732,7 @@ struct kvm_x86_ops {
 	int (*gmem_make_private)(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 				 kvm_pfn_t nr_pages);
 #endif
-#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_RECLAIM
+#if defined(CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT) || defined(CONFIG_HAVE_KVM_ARCH_GMEM_RECLAIM)
 	void (*gmem_make_shared)(kvm_pfn_t pfn, kvm_pfn_t nr_pages);
 #endif
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2292249570314..75e03a2f79db2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10653,6 +10653,11 @@ int kvm_arch_gmem_make_private(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 {
 	return kvm_x86_call(gmem_make_private)(kvm, gfn, pfn, nr_pages);
 }
+
+void kvm_arch_gmem_make_shared(kvm_pfn_t pfn, kvm_pfn_t nr_pages)
+{
+	kvm_x86_call(gmem_make_shared)(pfn, nr_pages);
+}
 #endif
 
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_RECLAIM
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ab87effdd221f..485f18454eb45 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2610,6 +2610,7 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm,
 
 int kvm_arch_gmem_make_private(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 			       kvm_pfn_t nr_pages);
+void kvm_arch_gmem_make_shared(kvm_pfn_t pfn, kvm_pfn_t nr_pages);
 #ifndef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
 #define kvm_arch_has_gmem_convert() false
 #endif
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index fe02c47c85fb5..d14a7024bdc7b 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -575,6 +575,43 @@ static bool kvm_gmem_has_outstanding_references(struct inode *inode,
 	return has_outstanding;
 }
 
+#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
+static void kvm_gmem_make_shared(struct inode *inode, pgoff_t start, pgoff_t end)
+{
+	struct folio_batch fbatch;
+	pgoff_t next = start;
+	int i;
+
+	folio_batch_init(&fbatch);
+	while (filemap_get_folios(inode->i_mapping, &next, end - 1, &fbatch)) {
+		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
+			struct folio *folio = fbatch.folios[i];
+			pgoff_t start_index, end_index;
+			kvm_pfn_t start_pfn;
+			kvm_pfn_t nr_pages;
+
+			start_index = max(start, folio->index);
+			end_index = min(end, folio_next_index(folio));
+			/*
+			 * end_index is either in folio or points to
+			 * the first page of the next folio. Hence,
+			 * all pages in range [start_index, end_index)
+			 * are contiguous.
+			 */
+			start_pfn = folio_file_pfn(folio, start_index);
+			nr_pages = end_index - start_index;
+
+			kvm_arch_gmem_make_shared(start_pfn, nr_pages);
+		}
+
+		folio_batch_release(&fbatch);
+		cond_resched();
+	}
+}
+#else
+static void kvm_gmem_make_shared(struct inode *inode, pgoff_t start, pgoff_t end) {}
+#endif
+
 static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
 				     size_t nr_pages, uint64_t attrs,
 				     pgoff_t *err_index)
@@ -624,7 +661,12 @@ static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
 
 	filter = to_private ? KVM_FILTER_SHARED : KVM_FILTER_PRIVATE;
 	kvm_gmem_invalidate_start(inode, start, end, filter);
+
+	if (!to_private && kvm_arch_has_gmem_convert())
+		kvm_gmem_make_shared(inode, start, end);
+
 	mas_store_prealloc(&mas, xa_mk_value(attrs));
+
 	kvm_gmem_invalidate_end(inode, start, end);
 out:
 	filemap_invalidate_unlock(mapping);

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 17/45] KVM: guest_memfd: Return early if range already has requested attributes

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Provide a function to check that a range has given attributes.

Optimize setting memory attributes by returning early if all pages in the
requested range already have the requested attributes.

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 virt/kvm/guest_memfd.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index d14a7024bdc7b..ac8e0c6d6e942 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -98,6 +98,24 @@ static bool kvm_gmem_is_shared_mem(struct inode *inode, pgoff_t index)
 	return !kvm_gmem_is_private_mem(inode, index);
 }
 
+static bool kvm_gmem_range_has_attributes(struct inode *inode,
+					  pgoff_t index, size_t nr_pages,
+					  u64 attributes)
+{
+	struct maple_tree *mt = &GMEM_I(inode)->attributes;
+	pgoff_t end = index + nr_pages - 1;
+	void *entry;
+
+	lockdep_assert(mt_lock_is_held(mt));
+
+	mt_for_each(mt, entry, index, end) {
+		if (kvm_gmem_get_attributes(inode, entry) != attributes)
+			return false;
+	}
+
+	return true;
+}
+
 /*
  * Returns a locked folio on success.  The caller is responsible for
  * setting the up-to-date flag before the memory is mapped into the guest.
@@ -623,12 +641,15 @@ static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
 	pgoff_t end = start + nr_pages;
 	struct maple_tree *mt;
 	struct ma_state mas;
-	int r;
+	int r = 0;
 
 	mt = &gi->attributes;
 
 	filemap_invalidate_lock(mapping);
 
+	if (kvm_gmem_range_has_attributes(inode, start, nr_pages, attrs))
+		goto out;
+
 	mas_init(&mas, mt, start);
 	r = kvm_gmem_mas_preallocate(&mas, attrs, start, nr_pages);
 	if (r) {

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 18/45] KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

A guest_memfd folio has no outstanding references if guest_memfd holds the
only references on it. Any other references on the folio may indicate
another user, and guest_memfd cannot convert it to private if there may be
an existing host user.

A folio will have outstanding references if it is present in a per-CPU
lru_add fbatch. guest_memfd does not actually participate in LRU, but
freshly-allocated folios are still added to the lru_add fbatch for batch
LRU statistics processing.

A folio may also have extra refcounts if it is on the mlock fbatch.

These two known "usages" of the folio are handled by calling
lru_cache_drain_for_folio, which drains both the lru_add and mlock
fbatches. After draining, if the refcount is still elevated, then there are
truly outstanding references.

If the page may be dma pinned, DMA is using it and hence there are
outstanding references. folio_maybe_dma_pinned() can have false positives,
but that's only with a significant number of refcounts, at which point
draining LRU is not going to move the needle - it can still be concluded
that the folio has outstanding references.

If the page is still mapped after guest_memfd tried to unmap it earlier in
the conversion process, it also has outstanding references.

Return true and exit early to avoid unnecessary draining in these 2 cases.

Provide a drain status to only drain once ever while processing a batch of
folios.

Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Suggested-by: David Hildenbrand <david@kernel.org>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 mm/folio.c             |  2 ++
 virt/kvm/guest_memfd.c | 30 ++++++++++++++++++++++--------
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/mm/folio.c b/mm/folio.c
index c02dcea9c03c2..50a6dbe55998e 100644
--- a/mm/folio.c
+++ b/mm/folio.c
@@ -33,6 +33,7 @@
 #include <linux/page_idle.h>
 #include <linux/local_lock.h>
 #include <linux/buffer_head.h>
+#include <linux/kvm_types.h>
 
 #include "internal.h"
 #include "page_alloc.h"
@@ -926,6 +927,7 @@ void lru_cache_drain_for_folio(const struct folio *folio,
 			*drained = LRU_CACHE_DRAINED_ALL;
 	}
 }
+EXPORT_SYMBOL_FOR_KVM(lru_cache_drain_for_folio);
 
 atomic_t lru_disable_count = ATOMIC_INIT(0);
 
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index ac8e0c6d6e942..1fe935aaef36f 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -8,6 +8,7 @@
 #include <linux/mempolicy.h>
 #include <linux/pseudo_fs.h>
 #include <linux/pagemap.h>
+#include <linux/swap.h>
 
 #include "kvm_mm.h"
 #include "guest_memfd.h"
@@ -556,10 +557,28 @@ static int kvm_gmem_mas_preallocate(struct ma_state *mas, u64 attributes,
 	return mas_preallocate(mas, xa_mk_value(attributes), GFP_KERNEL);
 }
 
+static bool __folio_has_outstanding_references(struct folio *folio,
+					       enum lru_cache_drained *drained)
+{
+	if (folio_maybe_dma_pinned(folio) || folio_mapped(folio))
+		return true;
+
+	/* 1 reference held by filemap_get_folios() in the folio batch. */
+	lru_cache_drain_for_folio(folio, 1, drained);
+
+	/*
+	 * Outstanding references are anything other than those from the page
+	 * cache, plus 1 temporary reference held by filemap_get_folios() in the
+	 * folio batch.
+	 */
+	return folio_ref_count(folio) != folio_nr_pages(folio) + 1;
+}
+
 static bool kvm_gmem_has_outstanding_references(struct inode *inode,
 						pgoff_t start, size_t nr_pages,
 						pgoff_t *err_index)
 {
+	enum lru_cache_drained drained = LRU_CACHE_NOT_DRAINED;
 	struct address_space *mapping = inode->i_mapping;
 	pgoff_t last = start + nr_pages - 1;
 	bool has_outstanding = false;
@@ -570,17 +589,12 @@ static bool kvm_gmem_has_outstanding_references(struct inode *inode,
 	folio_batch_init(&fbatch);
 
 	next = start;
-	while (has_outstanding && filemap_get_folios(mapping, &next, last, &fbatch)) {
+	while (!has_outstanding && filemap_get_folios(mapping, &next, last, &fbatch)) {
 		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
 			struct folio *folio = fbatch.folios[i];
 
-			/*
-			 * Outstanding references are anything other than those
-			 * from the page cache, plus 1 temporary reference held
-			 * by filemap_get_folios() in the folio batch.
-			 */
-			if (folio_ref_count(folio) != folio_nr_pages(folio) + 1) {
-				has_outstanding = true;
+			has_outstanding = __folio_has_outstanding_references(folio, &drained);
+			if (has_outstanding) {
 				*err_index = max(start, folio->index);
 				break;
 			}

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 18/45] KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check

[Hugh Dickins]

On Sun, 30 Aug 2026, Ackerley Tng via B4 Relay wrote:

> From: Ackerley Tng <ackerleytng@google.com>
> 
> A guest_memfd folio has no outstanding references if guest_memfd holds the
> only references on it. Any other references on the folio may indicate
> another user, and guest_memfd cannot convert it to private if there may be
> an existing host user.
> 
> A folio will have outstanding references if it is present in a per-CPU
> lru_add fbatch. guest_memfd does not actually participate in LRU, but
> freshly-allocated folios are still added to the lru_add fbatch for batch
> LRU statistics processing.
> 
> A folio may also have extra refcounts if it is on the mlock fbatch.
> 
> These two known "usages" of the folio are handled by calling
> lru_cache_drain_for_folio, which drains both the lru_add and mlock
> fbatches. After draining, if the refcount is still elevated, then there are
> truly outstanding references.
> 
> If the page may be dma pinned, DMA is using it and hence there are
> outstanding references. folio_maybe_dma_pinned() can have false positives,
> but that's only with a significant number of refcounts, at which point
> draining LRU is not going to move the needle - it can still be concluded
> that the folio has outstanding references.
> 
> If the page is still mapped after guest_memfd tried to unmap it earlier in
> the conversion process, it also has outstanding references.
> 
> Return true and exit early to avoid unnecessary draining in these 2 cases.
> 
> Provide a drain status to only drain once ever while processing a batch of
> folios.
> 
> Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> Suggested-by: David Hildenbrand <david@kernel.org>
> Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
> Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> ---
>  mm/folio.c             |  2 ++
>  virt/kvm/guest_memfd.c | 30 ++++++++++++++++++++++--------
>  2 files changed, 24 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/folio.c b/mm/folio.c
> index c02dcea9c03c2..50a6dbe55998e 100644
> --- a/mm/folio.c
> +++ b/mm/folio.c
> @@ -33,6 +33,7 @@
>  #include <linux/page_idle.h>
>  #include <linux/local_lock.h>
>  #include <linux/buffer_head.h>
> +#include <linux/kvm_types.h>
>  
>  #include "internal.h"
>  #include "page_alloc.h"
> @@ -926,6 +927,7 @@ void lru_cache_drain_for_folio(const struct folio *folio,
>  			*drained = LRU_CACHE_DRAINED_ALL;
>  	}
>  }
> +EXPORT_SYMBOL_FOR_KVM(lru_cache_drain_for_folio);
>  
>  atomic_t lru_disable_count = ATOMIC_INIT(0);
>  

I don't mind about the virt/kvm/guest_memfd.c part of it, but I'm finding
a KVM patchset modifying mm/folio.c there hard to deal with: and notice
Sean also suggesting to separate this part out.

As you know, I've worked up a patchset "mm/fbatch: drain lru_add_drain()
and _all()" which finally removes the problem lru_cache_drain_for_folio()
works around. In the initial version posted a week ago, there was no
lru_cache_drain_for_folio() in the tree. Now 7.3-rc1 has it, so I
intended a replacement 13/25 in my series, giving you just an empty
inline lru_cache_drain_for_folio() stub (and enum lru_cache_drained)
in linux/swap.h.

But that won't work for you, if you're adding an EXPORT_SYMBOL_FOR_KVM()
in mm/folio.c, and of course conflicts with my removals (in context both
above and below your EXPORT line). It's easy for me to remove what's in
mm/gup.c and mm/folio.c, but I cannot remove what is not yet there.

I've wasted hours on this, hoping not to trouble either of you; but
seeing now that I shall have to rebase anyway (an unrelated mlock fix),
I'm electing to take the only clean way out: I'm going to submit this
mm/folio.c part of your patch to Andrew tonight (with a shorter Cc list!),
in the hope that it can be accelerated into 7.3-rc2 (or at least get an
mm-stable stable base-commit id) which we can both work off independently.

Whether that's acceptable to Ackerley and to Andrew, I don't know
(just as we don't know when either of our patchsets will go further),
but let me try.

Thanks,
Hugh

[PATCH v12 19/45] KVM: guest_memfd: Zero page while getting pfn

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Move the folio initialization logic from kvm_gmem_get_pfn() into
__kvm_gmem_get_pfn() to also zero pages if the page is to be used in
kvm_gmem_populate().

With in-place conversion, the existing data in a guest_memfd page can be
populated into guest memory through platform-specific ioctls.

Without first zeroing the page obtained using __kvm_gmem_get_pfn(), it
might contain uninitialized host memory, which would leak to the guest if
the populate completes.

guest_memfd pages are zeroed at most once in the page's entire lifetime
with guest_memfd, and that is tracked using the uptodate flag.

Zeroing the page in __kvm_gmem_get_pfn() is chosen over zeroing in
kvm_gmem_get_folio() since other flows, such as a future write() syscall,
can get a page, write to the page and then set page uptodate without
zeroing.

There may be some performance penalty due to redundant zeroing, but this
would pale in comparison to the cost of actually assigning the page to the
VM.

This aligns with the concept of zeroing before first use - the other place
where zeroing happens is in kvm_gmem_fault_user_mapping().

On populate failure, the page is not re-zeroed, since on SNP, if firmware
rejects a CPUID page, the expected CPUID values provided by firmware are
returned to userspace via page contents. More generally, page contents may
be modified on populate failure.

Don't mark the page uptodate again after populating, since the page would
already be marked uptodate before the post_populate() call.

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 virt/kvm/guest_memfd.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 1fe935aaef36f..5db578fdce6af 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -1105,6 +1105,11 @@ static struct folio *__kvm_gmem_get_pfn(struct file *file,
 		return ERR_PTR(-EHWPOISON);
 	}
 
+	if (!folio_test_uptodate(folio)) {
+		clear_highpage(folio_page(folio, 0));
+		folio_mark_uptodate(folio);
+	}
+
 	*pfn = folio_file_pfn(folio, index);
 	if (max_order)
 		*max_order = 0;
@@ -1133,11 +1138,6 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
 		goto out;
 	}
 
-	if (!folio_test_uptodate(folio)) {
-		clear_highpage(folio_page(folio, 0));
-		folio_mark_uptodate(folio);
-	}
-
 	if (kvm_arch_has_gmem_convert() &&
 	    kvm_gmem_is_private_mem(file_inode(file), index))
 		r = kvm_arch_gmem_make_private(kvm, gfn, *pfn,
@@ -1179,8 +1179,6 @@ static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot,
 	}
 
 	ret = post_populate(kvm, gfn, pfn, src_page, opaque);
-	if (!ret)
-		folio_mark_uptodate(folio);
 
 out_put_folio:
 	folio_put(folio);

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 20/45] KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE

[Ackerley Tng via B4 Relay]

From: Michael Roth <michael.roth@amd.com>

Make the source page for populating an SNP guest_memfd instance optional
if in-place conversion/population is enabled.  If KVM can convert the page
in-place, then it's possible for guest memory to be initialized directly
from userspace by mmap()'ing the guest_memfd and writing to it while the
corresponding GPA ranges are in a 'shared' state, before converting them
to the 'private' state expected by KVM_SEV_SNP_LAUNCH_UPDATE.

Update the handling/documentation for KVM_SEV_SNP_LAUNCH_UPDATE to allow
for 'uaddr' to be set to NULL when in-place conversion is enabled, which
SNP_LAUNCH_UPDATE will then use to determine when it should/shouldn't
copy in data from a separate memory location. Continue to enforce
non-NULL when PRIVATE is tracked per-VM, not per-guest_memfd.

Signed-off-by: Michael Roth <michael.roth@amd.com>
[Moved condition to snp_launch_update]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 Documentation/virt/kvm/x86/amd-memory-encryption.rst | 14 ++++++++++----
 arch/x86/kvm/svm/sev.c                               | 11 ++++++-----
 virt/kvm/kvm_main.c                                  |  1 +
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
index bd04a908a8dbd..5977fbe33b98c 100644
--- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
@@ -503,7 +503,8 @@ secrets.
 
 It is required that the GPA ranges initialized by this command have had the
 KVM_MEMORY_ATTRIBUTE_PRIVATE attribute set in advance. See the documentation
-for KVM_SET_MEMORY_ATTRIBUTES for more details on this aspect.
+for KVM_SET_MEMORY_ATTRIBUTES/KVM_SET_MEMORY_ATTRIBUTES2 for more details on
+this aspect.
 
 Upon success, this command is not guaranteed to have processed the entire
 range requested. Instead, the ``gfn_start``, ``uaddr``, and ``len`` fields of
@@ -511,9 +512,14 @@ range requested. Instead, the ``gfn_start``, ``uaddr``, and ``len`` fields of
 remaining range that has yet to be processed. The caller should continue
 calling this command until those fields indicate the entire range has been
 processed, e.g. ``len`` is 0, ``gfn_start`` is equal to the last GFN in the
-range plus 1, and ``uaddr`` is the last byte of the userspace-provided source
-buffer address plus 1. In the case where ``type`` is KVM_SEV_SNP_PAGE_TYPE_ZERO,
-``uaddr`` will be ignored completely.
+range plus 1, and ``uaddr`` (if specified) is the last byte of the
+userspace-provided source buffer address plus 1.
+
+In the case where ``type`` is KVM_SEV_SNP_PAGE_TYPE_ZERO, ``uaddr`` will be
+ignored completely. For all other page types, ``uaddr`` is optional if in-place
+conversion is enabled (i.e. when the data had been written directly to
+guest_memfd while the page was in the shared state) and is required if in-place
+conversion is disabled.
 
 Parameters (in): struct  kvm_sev_snp_launch_update
 
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index dff684b88f153..63e8cfa9bf559 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2400,7 +2400,7 @@ static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 	 */
 	if (ret && !snp_page_reclaim(kvm, pfn) &&
 	    sev_populate_args->type == KVM_SEV_SNP_PAGE_TYPE_CPUID &&
-	    sev_populate_args->fw_error == SEV_RET_INVALID_PARAM) {
+	    sev_populate_args->fw_error == SEV_RET_INVALID_PARAM && src_page) {
 		void *src_vaddr = kmap_local_page(src_page);
 		void *dst_vaddr = kmap_local_pfn(pfn);
 
@@ -2433,8 +2433,8 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	if (copy_from_user(&params, u64_to_user_ptr(argp->data), sizeof(params)))
 		return -EFAULT;
 
-	pr_debug("%s: GFN start 0x%llx length 0x%llx type %d flags %d\n", __func__,
-		 params.gfn_start, params.len, params.type, params.flags);
+	pr_debug("%s: GFN start 0x%llx length 0x%llx type %d flags %d src %llx\n", __func__,
+		 params.gfn_start, params.len, params.type, params.flags, params.uaddr);
 
 	if (!params.len || !PAGE_ALIGNED(params.len) || params.flags ||
 	    (params.type != KVM_SEV_SNP_PAGE_TYPE_NORMAL &&
@@ -2446,7 +2446,8 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
 
 	if (params.type == KVM_SEV_SNP_PAGE_TYPE_ZERO)
 		src = NULL;
-	else if (!params.uaddr || !PAGE_ALIGNED(params.uaddr))
+	else if ((!gmem_in_place_conversion && !params.uaddr) ||
+		 !PAGE_ALIGNED(params.uaddr))
 		return -EINVAL;
 	else
 		src = u64_to_user_ptr(params.uaddr);
@@ -2493,7 +2494,7 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
 
 	params.gfn_start += count;
 	params.len -= count * PAGE_SIZE;
-	if (params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO)
+	if (src && params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO)
 		params.uaddr += count * PAGE_SIZE;
 
 	if (copy_to_user(u64_to_user_ptr(argp->data), &params, sizeof(params)))
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1ea8198821917..05c518c9b8078 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -104,6 +104,7 @@ module_param(allow_unsafe_mappings, bool, 0444);
 
 #ifdef kvm_arch_has_private_mem
 bool __ro_after_init gmem_in_place_conversion = false;
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(gmem_in_place_conversion);
 #endif
 
 /*

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 21/45] KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Update tdx_gmem_post_populate() to handle cases where userspace requests
"no source page". To handle "no source page", populate (perform
TDH.MEM.PAGE.ADD) using memory in-place at the target PFN.

Allow "no source page" only when gmem_in_place_conversion is enabled,
because retroactively adding support for out-of-place conversion would mean
requiring a userspace update for a feature that's being deprecated.

Also, KVM supporting "no source page" without in-place conversion would
effectively be an obscure zero-page optimization that relies on the page
being zeroed when it is allocated by guest_memfd.

Rejecting "no source page" without in-place conversion scenario is valuable
for KVM developers since it helps newcomers understand what exactly is and
isn't possible.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Tested-by: Yan Zhao <yan.y.zhao@intel.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 Documentation/virt/kvm/x86/intel-tdx.rst | 4 ++++
 arch/x86/kvm/vmx/tdx.c                   | 8 +++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/Documentation/virt/kvm/x86/intel-tdx.rst b/Documentation/virt/kvm/x86/intel-tdx.rst
index 6a222e9d09541..d8d9409120e61 100644
--- a/Documentation/virt/kvm/x86/intel-tdx.rst
+++ b/Documentation/virt/kvm/x86/intel-tdx.rst
@@ -158,6 +158,10 @@ KVM_TDX_INIT_MEM_REGION
 Initialize @nr_pages TDX guest private memory starting from @gpa with userspace
 provided data from @source_addr. @source_addr must be PAGE_SIZE-aligned.
 
+If guest_memfd in-place conversion is enabled, pass 0 for @source_addr
+to represent "no source page". A source page is required if in-place
+conversion is not enabled or not supported.
+
 Note, before calling this sub command, memory attribute of the range
 [gpa, gpa + nr_pages] needs to be private.  Userspace can use
 KVM_SET_MEMORY_ATTRIBUTES to set the attribute.
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index b272c20586a74..7654a9f5fa128 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -3189,7 +3189,7 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 	if (KVM_BUG_ON(kvm_tdx->page_add_src, kvm))
 		return -EIO;
 
-	kvm_tdx->page_add_src = src_page;
+	kvm_tdx->page_add_src = src_page ?: pfn_to_page(pfn);
 	ret = kvm_tdp_mmu_map_private_pfn(arg->vcpu, gfn, pfn);
 	kvm_tdx->page_add_src = NULL;
 
@@ -3235,7 +3235,8 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c
 	if (copy_from_user(&region, u64_to_user_ptr(cmd->data), sizeof(region)))
 		return -EFAULT;
 
-	if (!PAGE_ALIGNED(region.source_addr) || !region.source_addr ||
+	if (!PAGE_ALIGNED(region.source_addr) ||
+	    (!gmem_in_place_conversion && !region.source_addr) ||
 	    !PAGE_ALIGNED(region.gpa) || !region.nr_pages ||
 	    region.gpa + (region.nr_pages << PAGE_SHIFT) <= region.gpa ||
 	    !vt_is_tdx_private_gpa(kvm, region.gpa) ||
@@ -3266,7 +3267,8 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c
 			break;
 		}
 
-		region.source_addr += PAGE_SIZE;
+		if (region.source_addr)
+			region.source_addr += PAGE_SIZE;
 		region.gpa += PAGE_SIZE;
 		region.nr_pages--;
 

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 22/45] KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Bury KVM_VM_MEMORY_ATTRIBUTES in x86 to discourage other architectures
from adding support for per-VM memory attributes, because tracking private
vs. shared memory on a per-VM basis is now deprecated in favor of tracking
on a per-guest_memfd basis, and while RWX memory attributes are on the
horizon, they too are expected to be x86-only.

This will also allow modifying KVM_VM_MEMORY_ATTRIBUTES to be
user-selectable (in x86) without creating weirdness in KVM's Kconfigs.
Now that guest_memfd supports in-place conversions, it's entirely possible
to run x86 CoCo VMs without support for KVM_VM_MEMORY_ATTRIBUTES.

Leave the code itself in common KVM so that it's trivial to undo this
change if new per-VM attributes do come along.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 arch/x86/kvm/Kconfig | 3 +++
 virt/kvm/Kconfig     | 3 ---
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 2f8e1b5a8a72c..abb108886733a 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -80,6 +80,9 @@ config KVM_WERROR
 
 	  If in doubt, say "N".
 
+config KVM_VM_MEMORY_ATTRIBUTES
+	bool
+
 config KVM_SW_PROTECTED_VM
 	bool "Enable support for KVM software-protected VMs"
 	depends on EXPERT
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index df575449d97b5..a0678ef8ee3f5 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -100,9 +100,6 @@ config KVM_ELIDE_TLB_FLUSH_IF_YOUNG
 config KVM_MMU_LOCKLESS_AGING
        bool
 
-config KVM_VM_MEMORY_ATTRIBUTES
-       bool
-
 config KVM_GUEST_MEMFD
        select XARRAY_MULTI
        bool

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 23/45] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Allow the user to disable KVM_VM_MEMORY_ATTRIBUTES even when KVM supports
PRIVATE and SHARED attributes, and expose gmem_in_place_conversion as a
module parameter when per-VM attributes are supported.  I.e. let userspace
enable in-place PRIVATE<=>SHARED conversion of guest_memfd pages.

Provide both a Kconfig option and a (conditional) module param so that
deployments that use a custom kernel can fully disable per-VM tracking,
while not forcing distros to ship two separate kernels in order to provide
backwards compatibility for downstream users.

Don't allow running VMs with mixed tracking for a given instance of KVM,
i.e. disallow toggling the module param after KVM is loaded, as the extra
complexity needed to handle per-VM behavior far outweighs any potential
benefit.  E.g. neither TDX nor SNP supports live migration, so in effect
the requirement is that existing deployments that want to support both the
old and the new models would need to tell their VMM which flavor of
tracking to use.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
[Define module_param only if CONFIG_KVM_VM_MEMORY_ATTRIBUTES is enabled]
Suggested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 25 +++++++++++++++++++++++++
 arch/x86/include/asm/kvm_host.h                 |  4 +++-
 arch/x86/kvm/Kconfig                            | 14 ++++++++++----
 virt/kvm/kvm_main.c                             |  5 ++++-
 4 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 68647ff4bdd24..b5719714458fb 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3156,6 +3156,31 @@ Kernel parameters
 	kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
 				   Default is false (don't support).
 
+	kvm.gmem_in_place_conversion=
+			[KVM] Controls whether KVM enables in-place conversion
+			support for guest_memfd and tracks the private/shared
+			state of memory per guest_memfd instead of per VM.
+
+			If enabled, KVM enables the KVM_SET_MEMORY_ATTRIBUTES2
+			ioctl on guest_memfd file descriptors and disables the
+			legacy VM-scoped KVM_SET_MEMORY_ATTRIBUTES ioctl for
+			private memory state tracking. Only the
+			KVM_MEMORY_ATTRIBUTE_PRIVATE attribute moves to
+			per-guest_memfd tracking; other attributes remain
+			per-VM.
+
+			This parameter toggles KVM's in-place conversion
+			capability support. Whether a VMM uses separate backends
+			or out-of-place memory management is determined by
+			userspace VMM design.
+
+			Note, this parameter is only available when
+			CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y. When
+			CONFIG_KVM_VM_MEMORY_ATTRIBUTES is not set, in-place
+			conversion is unconditionally enabled.
+
+			Default is Y (on).
+
 	kvm.nx_huge_pages=
 			[KVM] Controls the software workaround for the
 			X86_BUG_ITLB_MULTIHIT bug.
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 83e26ce45fb79..e840418427a1d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1851,7 +1851,9 @@ enum kvm_intr_type {
 	((vcpu) && (vcpu)->arch.handling_intr_from_guest && \
 	 (!!in_nmi() == ((vcpu)->arch.handling_intr_from_guest == KVM_HANDLING_NMI)))
 
-#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+#if defined(CONFIG_KVM_SW_PROTECTED_VM) ||	\
+    defined(CONFIG_KVM_INTEL_TDX) ||		\
+    defined(CONFIG_KVM_AMD_SEV)
 #define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem)
 #endif
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index abb108886733a..2c3c22aeafa54 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -81,13 +81,21 @@ config KVM_WERROR
 	  If in doubt, say "N".
 
 config KVM_VM_MEMORY_ATTRIBUTES
-	bool
+	bool "Enable per-VM PRIVATE vs. SHARED attributes (for CoCo VMs)"
+	depends on KVM_SW_PROTECTED_VM || KVM_INTEL_TDX || KVM_AMD_SEV
+	help
+	  Enable support for tracking PRIVATE vs. SHARED memory using per-VM
+	  memory attributes.  Using per-VM attributes is deprecated in favor of
+	  tracking PRIVATE state in guest_memfd.  Select this if you need to run
+	  CoCo VMs using a VMM that doesn't support guest_memfd memory
+	  attributes.
+
+	  If unsure, say N.
 
 config KVM_SW_PROTECTED_VM
 	bool "Enable support for KVM software-protected VMs"
 	depends on EXPERT
 	depends on KVM_X86 && X86_64
-	select KVM_VM_MEMORY_ATTRIBUTES
 	help
 	  Enable support for KVM software-protected VMs.  Currently, software-
 	  protected VMs are purely a development and testing vehicle for
@@ -138,7 +146,6 @@ config KVM_INTEL_TDX
 	bool "Intel Trust Domain Extensions (TDX) support"
 	default y
 	depends on INTEL_TDX_HOST
-	select KVM_VM_MEMORY_ATTRIBUTES
 	select HAVE_KVM_ARCH_GMEM_POPULATE
 	help
 	  Provides support for launching Intel Trust Domain Extensions (TDX)
@@ -162,7 +169,6 @@ config KVM_AMD_SEV
 	depends on KVM_AMD && X86_64
 	depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
 	select ARCH_HAS_CC_PLATFORM
-	select KVM_VM_MEMORY_ATTRIBUTES
 	select HAVE_KVM_ARCH_GMEM_CONVERT
 	select HAVE_KVM_ARCH_GMEM_RECLAIM
 	select HAVE_KVM_ARCH_GMEM_INVALIDATE
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 05c518c9b8078..929fd3e1a01e6 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -103,7 +103,10 @@ static bool __ro_after_init allow_unsafe_mappings;
 module_param(allow_unsafe_mappings, bool, 0444);
 
 #ifdef kvm_arch_has_private_mem
-bool __ro_after_init gmem_in_place_conversion = false;
+bool __ro_after_init gmem_in_place_conversion = !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES);
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+module_param(gmem_in_place_conversion, bool, 0444);
+#endif
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(gmem_in_place_conversion);
 #endif
 

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 23/45] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes

[Fuad Tabba]

Hi Sean, Ackerley,

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
...
> +       kvm.gmem_in_place_conversion=
> +                       [KVM] Controls whether KVM enables in-place conversion
> +                       support for guest_memfd and tracks the private/shared
> +                       state of memory per guest_memfd instead of per VM.
> +
> +                       If enabled, KVM enables the KVM_SET_MEMORY_ATTRIBUTES2
> +                       ioctl on guest_memfd file descriptors and disables the
> +                       legacy VM-scoped KVM_SET_MEMORY_ATTRIBUTES ioctl for
> +                       private memory state tracking. Only the
> +                       KVM_MEMORY_ATTRIBUTE_PRIVATE attribute moves to
> +                       per-guest_memfd tracking; other attributes remain
> +                       per-VM.
> +
> +                       This parameter toggles KVM's in-place conversion
> +                       capability support. Whether a VMM uses separate backends
> +                       or out-of-place memory management is determined by
> +                       userspace VMM design.
> +
> +                       Note, this parameter is only available when
> +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y. When
> +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES is not set, in-place
> +                       conversion is unconditionally enabled.
> +
> +                       Default is Y (on).

The parameter is only settable when CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y, and
in that config gmem_in_place_conversion initialises to
!IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES), i.e. N, not Y. Is the doc line
wrong, or is N-by-default not what was intended here?

Cheers,
/fuad

> +
>         kvm.nx_huge_pages=
>                         [KVM] Controls the software workaround for the
>                         X86_BUG_ITLB_MULTIHIT bug.
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 83e26ce45fb79..e840418427a1d 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1851,7 +1851,9 @@ enum kvm_intr_type {
>         ((vcpu) && (vcpu)->arch.handling_intr_from_guest && \
>          (!!in_nmi() == ((vcpu)->arch.handling_intr_from_guest == KVM_HANDLING_NMI)))
>
> -#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
> +#if defined(CONFIG_KVM_SW_PROTECTED_VM) ||     \
> +    defined(CONFIG_KVM_INTEL_TDX) ||           \
> +    defined(CONFIG_KVM_AMD_SEV)
>  #define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem)
>  #endif
>  #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index abb108886733a..2c3c22aeafa54 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -81,13 +81,21 @@ config KVM_WERROR
>           If in doubt, say "N".
>
>  config KVM_VM_MEMORY_ATTRIBUTES
> -       bool
> +       bool "Enable per-VM PRIVATE vs. SHARED attributes (for CoCo VMs)"
> +       depends on KVM_SW_PROTECTED_VM || KVM_INTEL_TDX || KVM_AMD_SEV
> +       help
> +         Enable support for tracking PRIVATE vs. SHARED memory using per-VM
> +         memory attributes.  Using per-VM attributes is deprecated in favor of
> +         tracking PRIVATE state in guest_memfd.  Select this if you need to run
> +         CoCo VMs using a VMM that doesn't support guest_memfd memory
> +         attributes.
> +
> +         If unsure, say N.
>
>  config KVM_SW_PROTECTED_VM
>         bool "Enable support for KVM software-protected VMs"
>         depends on EXPERT
>         depends on KVM_X86 && X86_64
> -       select KVM_VM_MEMORY_ATTRIBUTES
>         help
>           Enable support for KVM software-protected VMs.  Currently, software-
>           protected VMs are purely a development and testing vehicle for
> @@ -138,7 +146,6 @@ config KVM_INTEL_TDX
>         bool "Intel Trust Domain Extensions (TDX) support"
>         default y
>         depends on INTEL_TDX_HOST
> -       select KVM_VM_MEMORY_ATTRIBUTES
>         select HAVE_KVM_ARCH_GMEM_POPULATE
>         help
>           Provides support for launching Intel Trust Domain Extensions (TDX)
> @@ -162,7 +169,6 @@ config KVM_AMD_SEV
>         depends on KVM_AMD && X86_64
>         depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
>         select ARCH_HAS_CC_PLATFORM
> -       select KVM_VM_MEMORY_ATTRIBUTES
>         select HAVE_KVM_ARCH_GMEM_CONVERT
>         select HAVE_KVM_ARCH_GMEM_RECLAIM
>         select HAVE_KVM_ARCH_GMEM_INVALIDATE
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 05c518c9b8078..929fd3e1a01e6 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -103,7 +103,10 @@ static bool __ro_after_init allow_unsafe_mappings;
>  module_param(allow_unsafe_mappings, bool, 0444);
>
>  #ifdef kvm_arch_has_private_mem
> -bool __ro_after_init gmem_in_place_conversion = false;
> +bool __ro_after_init gmem_in_place_conversion = !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES);
> +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
> +module_param(gmem_in_place_conversion, bool, 0444);
> +#endif
>  EXPORT_SYMBOL_FOR_KVM_INTERNAL(gmem_in_place_conversion);
>  #endif
>
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

Re: [PATCH v12 23/45] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes

[Sean Christopherson]

On Tue, Sep 01, 2026, Fuad Tabba wrote:
> Hi Sean, Ackerley,
> 
> On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
> <devnull+ackerleytng.google.com@kernel.org> wrote:
> ...
> > +       kvm.gmem_in_place_conversion=
> > +                       [KVM] Controls whether KVM enables in-place conversion
> > +                       support for guest_memfd and tracks the private/shared
> > +                       state of memory per guest_memfd instead of per VM.
> > +
> > +                       If enabled, KVM enables the KVM_SET_MEMORY_ATTRIBUTES2
> > +                       ioctl on guest_memfd file descriptors and disables the
> > +                       legacy VM-scoped KVM_SET_MEMORY_ATTRIBUTES ioctl for
> > +                       private memory state tracking. Only the
> > +                       KVM_MEMORY_ATTRIBUTE_PRIVATE attribute moves to
> > +                       per-guest_memfd tracking; other attributes remain
> > +                       per-VM.
> > +
> > +                       This parameter toggles KVM's in-place conversion
> > +                       capability support. Whether a VMM uses separate backends
> > +                       or out-of-place memory management is determined by
> > +                       userspace VMM design.
> > +
> > +                       Note, this parameter is only available when
> > +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y. When
> > +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES is not set, in-place
> > +                       conversion is unconditionally enabled.
> > +
> > +                       Default is Y (on).
> 
> The parameter is only settable when CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y, and
> in that config gmem_in_place_conversion initialises to
> !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES), i.e. N, not Y. Is the doc line
> wrong, or is N-by-default not what was intended here?

The doc is wrong.  The intent is to maintain backwards compatibility with existing
deployments if KVM_VM_MEMORY_ATTRIBUTES=y.

> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 05c518c9b8078..929fd3e1a01e6 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -103,7 +103,10 @@ static bool __ro_after_init allow_unsafe_mappings;
> >  module_param(allow_unsafe_mappings, bool, 0444);
> >
> >  #ifdef kvm_arch_has_private_mem
> > -bool __ro_after_init gmem_in_place_conversion = false;
> > +bool __ro_after_init gmem_in_place_conversion = !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES);
> > +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
> > +module_param(gmem_in_place_conversion, bool, 0444);
> > +#endif
> >  EXPORT_SYMBOL_FOR_KVM_INTERNAL(gmem_in_place_conversion);
> >  #endif

Re: [PATCH v12 23/45] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes

[Fuad Tabba]

On Tue, 1 Sept 2026 at 19:26, Sean Christopherson <seanjc@google.com> wrote:
>
> On Tue, Sep 01, 2026, Fuad Tabba wrote:
> > Hi Sean, Ackerley,
> >
> > On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
> > <devnull+ackerleytng.google.com@kernel.org> wrote:
> > ...
> > > +       kvm.gmem_in_place_conversion=
> > > +                       [KVM] Controls whether KVM enables in-place conversion
> > > +                       support for guest_memfd and tracks the private/shared
> > > +                       state of memory per guest_memfd instead of per VM.
> > > +
> > > +                       If enabled, KVM enables the KVM_SET_MEMORY_ATTRIBUTES2
> > > +                       ioctl on guest_memfd file descriptors and disables the
> > > +                       legacy VM-scoped KVM_SET_MEMORY_ATTRIBUTES ioctl for
> > > +                       private memory state tracking. Only the
> > > +                       KVM_MEMORY_ATTRIBUTE_PRIVATE attribute moves to
> > > +                       per-guest_memfd tracking; other attributes remain
> > > +                       per-VM.
> > > +
> > > +                       This parameter toggles KVM's in-place conversion
> > > +                       capability support. Whether a VMM uses separate backends
> > > +                       or out-of-place memory management is determined by
> > > +                       userspace VMM design.
> > > +
> > > +                       Note, this parameter is only available when
> > > +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y. When
> > > +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES is not set, in-place
> > > +                       conversion is unconditionally enabled.
> > > +
> > > +                       Default is Y (on).
> >
> > The parameter is only settable when CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y, and
> > in that config gmem_in_place_conversion initialises to
> > !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES), i.e. N, not Y. Is the doc line
> > wrong, or is N-by-default not what was intended here?
>
> The doc is wrong.  The intent is to maintain backwards compatibility with existing
> deployments if KVM_VM_MEMORY_ATTRIBUTES=y.

That explains it. Thanks.
/fuad

>
> > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > > index 05c518c9b8078..929fd3e1a01e6 100644
> > > --- a/virt/kvm/kvm_main.c
> > > +++ b/virt/kvm/kvm_main.c
> > > @@ -103,7 +103,10 @@ static bool __ro_after_init allow_unsafe_mappings;
> > >  module_param(allow_unsafe_mappings, bool, 0444);
> > >
> > >  #ifdef kvm_arch_has_private_mem
> > > -bool __ro_after_init gmem_in_place_conversion = false;
> > > +bool __ro_after_init gmem_in_place_conversion = !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES);
> > > +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
> > > +module_param(gmem_in_place_conversion, bool, 0444);
> > > +#endif
> > >  EXPORT_SYMBOL_FOR_KVM_INTERNAL(gmem_in_place_conversion);
> > >  #endif

Re: [PATCH v12 23/45] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes

[Binbin Wu]

On 9/2/2026 2:26 AM, Sean Christopherson wrote:
> On Tue, Sep 01, 2026, Fuad Tabba wrote:
>> Hi Sean, Ackerley,
>>
>> On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
>> <devnull+ackerleytng.google.com@kernel.org> wrote:
>> ...
>>> +       kvm.gmem_in_place_conversion=
>>> +                       [KVM] Controls whether KVM enables in-place conversion
>>> +                       support for guest_memfd and tracks the private/shared
>>> +                       state of memory per guest_memfd instead of per VM.
>>> +
>>> +                       If enabled, KVM enables the KVM_SET_MEMORY_ATTRIBUTES2
>>> +                       ioctl on guest_memfd file descriptors and disables the
>>> +                       legacy VM-scoped KVM_SET_MEMORY_ATTRIBUTES ioctl for
>>> +                       private memory state tracking. Only the
>>> +                       KVM_MEMORY_ATTRIBUTE_PRIVATE attribute moves to
>>> +                       per-guest_memfd tracking; other attributes remain
>>> +                       per-VM.
>>> +
>>> +                       This parameter toggles KVM's in-place conversion
>>> +                       capability support. Whether a VMM uses separate backends
>>> +                       or out-of-place memory management is determined by
>>> +                       userspace VMM design.
>>> +
>>> +                       Note, this parameter is only available when
>>> +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y. When
>>> +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES is not set, in-place
>>> +                       conversion is unconditionally enabled.
>>> +
>>> +                       Default is Y (on).
>>
>> The parameter is only settable when CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y, and
>> in that config gmem_in_place_conversion initialises to
>> !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES), i.e. N, not Y. Is the doc line
>> wrong, or is N-by-default not what was intended here?
> 
> The doc is wrong.  The intent is to maintain backwards compatibility with existing
> deployments if KVM_VM_MEMORY_ATTRIBUTES=y.
> 

Will it result in the situation that kernel builds with CONFIG_KVM_VM_MEMORY_ATTRIBUTES
enabled by default for backwards compatibility, which requires users to explicitly enable 
gmem_in_place_conversion by the kernel option? Then it effectively disables
gmem_in_place_conversion by default.

But I guess it's OK for CSPs since they know what they want.


>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>>> index 05c518c9b8078..929fd3e1a01e6 100644
>>> --- a/virt/kvm/kvm_main.c
>>> +++ b/virt/kvm/kvm_main.c
>>> @@ -103,7 +103,10 @@ static bool __ro_after_init allow_unsafe_mappings;
>>>  module_param(allow_unsafe_mappings, bool, 0444);
>>>
>>>  #ifdef kvm_arch_has_private_mem
>>> -bool __ro_after_init gmem_in_place_conversion = false;
>>> +bool __ro_after_init gmem_in_place_conversion = !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES);
>>> +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
>>> +module_param(gmem_in_place_conversion, bool, 0444);
>>> +#endif
>>>  EXPORT_SYMBOL_FOR_KVM_INTERNAL(gmem_in_place_conversion);
>>>  #endif
> 

Re: [PATCH v12 23/45] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes

[Sean Christopherson]

On Wed, Sep 02, 2026, Binbin Wu wrote:
> On 9/2/2026 2:26 AM, Sean Christopherson wrote:
> > On Tue, Sep 01, 2026, Fuad Tabba wrote:
> >> Hi Sean, Ackerley,
> >>
> >> On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
> >> <devnull+ackerleytng.google.com@kernel.org> wrote:
> >> ...
> >>> +       kvm.gmem_in_place_conversion=
> >>> +                       [KVM] Controls whether KVM enables in-place conversion
> >>> +                       support for guest_memfd and tracks the private/shared
> >>> +                       state of memory per guest_memfd instead of per VM.
> >>> +
> >>> +                       If enabled, KVM enables the KVM_SET_MEMORY_ATTRIBUTES2
> >>> +                       ioctl on guest_memfd file descriptors and disables the
> >>> +                       legacy VM-scoped KVM_SET_MEMORY_ATTRIBUTES ioctl for
> >>> +                       private memory state tracking. Only the
> >>> +                       KVM_MEMORY_ATTRIBUTE_PRIVATE attribute moves to
> >>> +                       per-guest_memfd tracking; other attributes remain
> >>> +                       per-VM.
> >>> +
> >>> +                       This parameter toggles KVM's in-place conversion
> >>> +                       capability support. Whether a VMM uses separate backends
> >>> +                       or out-of-place memory management is determined by
> >>> +                       userspace VMM design.
> >>> +
> >>> +                       Note, this parameter is only available when
> >>> +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y. When
> >>> +                       CONFIG_KVM_VM_MEMORY_ATTRIBUTES is not set, in-place
> >>> +                       conversion is unconditionally enabled.
> >>> +
> >>> +                       Default is Y (on).
> >>
> >> The parameter is only settable when CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y, and
> >> in that config gmem_in_place_conversion initialises to
> >> !IS_ENABLED(CONFIG_KVM_VM_MEMORY_ATTRIBUTES), i.e. N, not Y. Is the doc line
> >> wrong, or is N-by-default not what was intended here?
> > 
> > The doc is wrong.  The intent is to maintain backwards compatibility with existing
> > deployments if KVM_VM_MEMORY_ATTRIBUTES=y.
> > 
> 
> Will it result in the situation that kernel builds with CONFIG_KVM_VM_MEMORY_ATTRIBUTES
> enabled by default for backwards compatibility, which requires users to explicitly enable 
> gmem_in_place_conversion by the kernel option? Then it effectively disables
> gmem_in_place_conversion by default.

Yes.  My intent/expectation is that the only reason to build with
CONFIG_KVM_VM_MEMORY_ATTRIBUTES=y is for backwards compatibility, and so it makes
sense to have the existing behavior be the default.  If a deployment only wants
the new behavior, then it can simply build with CONFIG_KVM_VM_MEMORY_ATTRIBUTES=n.

Folks that want only the new behavior but are using a distro/pre-built kernel will
need to manually enable in-place conversion, but that's not too onerous, and it's
simply not feasible to provide defaults that work for every possible scenario.

> But I guess it's OK for CSPs since they know what they want.

Yep.

[PATCH v12 24/45] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Now that guest_memfd supports tracking private vs. shared within gmem
itself, allow userspace to specify INIT_SHARED on a guest_memfd instance
for x86 Confidential Computing (CoCo) VMs, so long as in-place conversion
is enabled, i.e. when it's actually possible for a guest_memfd instance to
contain shared memory.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 arch/x86/kvm/x86.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 75e03a2f79db2..c081e4b9b25de 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10637,14 +10637,15 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
 }
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
-/*
- * KVM doesn't yet support initializing guest_memfd memory as shared for VMs
- * with private memory (the private vs. shared tracking needs to be moved into
- * guest_memfd).
- */
 bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm)
 {
-	return !kvm_arch_has_private_mem(kvm);
+	/*
+	 * INIT_SHARED is supported if in-place conversion is enabled, or if
+	 * the VM doesn't support private memory.  If the VM has private memory
+	 * and in-place conversion is disabled, then guest_memfd can _only_ be
+	 * used for private memory.
+	 */
+	return gmem_in_place_conversion || !kvm_arch_has_private_mem(kvm);
 }
 
 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 25/45] KVM: selftests: Create gmem fd before "regular" fd when adding memslot

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

When adding a memslot associated with a guest_memfd instance, create/dup
the guest_memfd before creating the "normal" backing file.  This will allow
dup'ing the gmem fd as the normal fd when guest_memfd supports mmap(),
i.e. to make guest_memfd the _only_ backing source for the memslot.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 45 +++++++++++++++---------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 9ddc047d5c275..3413d45e34faf 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1077,6 +1077,29 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 	if (alignment > 1)
 		region->mmap_size += alignment;
 
+	if (flags & KVM_MEM_GUEST_MEMFD) {
+		if (guest_memfd < 0) {
+			u32 guest_memfd_flags = 0;
+
+			TEST_ASSERT(!guest_memfd_offset,
+				    "Offset must be zero when creating new guest_memfd");
+			guest_memfd = vm_create_guest_memfd(vm, mem_size, guest_memfd_flags);
+		} else {
+			/*
+			 * Install a unique fd for each memslot so that the fd
+			 * can be closed when the region is deleted without
+			 * needing to track if the fd is owned by the framework
+			 * or by the caller.
+			 */
+			guest_memfd = kvm_dup(guest_memfd);
+		}
+
+		region->region.guest_memfd = guest_memfd;
+		region->region.guest_memfd_offset = guest_memfd_offset;
+	} else {
+		region->region.guest_memfd = -1;
+	}
+
 	region->fd = -1;
 	if (backing_src_is_shared(src_type))
 		region->fd = kvm_memfd_alloc(region->mmap_size,
@@ -1106,28 +1129,6 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 
 	region->backing_src_type = src_type;
 
-	if (flags & KVM_MEM_GUEST_MEMFD) {
-		if (guest_memfd < 0) {
-			u32 guest_memfd_flags = 0;
-			TEST_ASSERT(!guest_memfd_offset,
-				    "Offset must be zero when creating new guest_memfd");
-			guest_memfd = vm_create_guest_memfd(vm, mem_size, guest_memfd_flags);
-		} else {
-			/*
-			 * Install a unique fd for each memslot so that the fd
-			 * can be closed when the region is deleted without
-			 * needing to track if the fd is owned by the framework
-			 * or by the caller.
-			 */
-			guest_memfd = kvm_dup(guest_memfd);
-		}
-
-		region->region.guest_memfd = guest_memfd;
-		region->region.guest_memfd_offset = guest_memfd_offset;
-	} else {
-		region->region.guest_memfd = -1;
-	}
-
 	region->unused_phy_pages = sparsebit_alloc();
 	if (vm_arch_has_protected_memory(vm))
 		region->protected_phy_pages = sparsebit_alloc();

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 26/45] KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset}

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Rename local variables and function parameters for the guest memory file
descriptor and its offset to use a "gmem_" prefix instead of
"guest_memfd_".

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/include/kvm_util.h |  6 +++---
 tools/testing/selftests/kvm/lib/kvm_util.c     | 26 +++++++++++++-------------
 2 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 5a7a455b53875..cf49a84de02e8 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -690,17 +690,17 @@ int __vm_set_user_memory_region(struct kvm_vm *vm, u32 slot, u32 flags,
 				gpa_t gpa, u64 size, void *hva);
 void vm_set_user_memory_region2(struct kvm_vm *vm, u32 slot, u32 flags,
 				gpa_t gpa, u64 size, void *hva,
-				u32 guest_memfd, u64 guest_memfd_offset);
+				u32 gmem_fd, u64 gmem_offset);
 int __vm_set_user_memory_region2(struct kvm_vm *vm, u32 slot, u32 flags,
 				 gpa_t gpa, u64 size, void *hva,
-				 u32 guest_memfd, u64 guest_memfd_offset);
+				 u32 gmem_fd, u64 gmem_offset);
 
 void vm_userspace_mem_region_add(struct kvm_vm *vm,
 				 enum vm_mem_backing_src_type src_type,
 				 gpa_t gpa, u32 slot, u64 npages, u32 flags);
 void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 		gpa_t gpa, u32 slot, u64 npages, u32 flags,
-		int guest_memfd_fd, u64 guest_memfd_offset);
+		int gmem_fd, u64 gmem_offset);
 
 #ifndef vm_arch_has_protected_memory
 static inline bool vm_arch_has_protected_memory(struct kvm_vm *vm)
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 3413d45e34faf..af501a27211a2 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -970,7 +970,7 @@ void vm_set_user_memory_region(struct kvm_vm *vm, u32 slot, u32 flags,
 
 int __vm_set_user_memory_region2(struct kvm_vm *vm, u32 slot, u32 flags,
 				 gpa_t gpa, u64 size, void *hva,
-				 u32 guest_memfd, u64 guest_memfd_offset)
+				 u32 gmem_fd, u64 gmem_offset)
 {
 	struct kvm_userspace_memory_region2 region = {
 		.slot = slot,
@@ -978,8 +978,8 @@ int __vm_set_user_memory_region2(struct kvm_vm *vm, u32 slot, u32 flags,
 		.guest_phys_addr = gpa,
 		.memory_size = size,
 		.userspace_addr = (uintptr_t)hva,
-		.guest_memfd = guest_memfd,
-		.guest_memfd_offset = guest_memfd_offset,
+		.guest_memfd = gmem_fd,
+		.guest_memfd_offset = gmem_offset,
 	};
 
 	TEST_REQUIRE_SET_USER_MEMORY_REGION2();
@@ -989,10 +989,10 @@ int __vm_set_user_memory_region2(struct kvm_vm *vm, u32 slot, u32 flags,
 
 void vm_set_user_memory_region2(struct kvm_vm *vm, u32 slot, u32 flags,
 				gpa_t gpa, u64 size, void *hva,
-				u32 guest_memfd, u64 guest_memfd_offset)
+				u32 gmem_fd, u64 gmem_offset)
 {
 	int ret = __vm_set_user_memory_region2(vm, slot, flags, gpa, size, hva,
-					       guest_memfd, guest_memfd_offset);
+					       gmem_fd, gmem_offset);
 
 	TEST_ASSERT(!ret, "KVM_SET_USER_MEMORY_REGION2 failed, errno = %d (%s)",
 		    errno, strerror(errno));
@@ -1002,7 +1002,7 @@ void vm_set_user_memory_region2(struct kvm_vm *vm, u32 slot, u32 flags,
 /* FIXME: This thing needs to be ripped apart and rewritten. */
 void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 		gpa_t gpa, u32 slot, u64 npages, u32 flags,
-		int guest_memfd, u64 guest_memfd_offset)
+		int gmem_fd, u64 gmem_offset)
 {
 	int ret;
 	struct userspace_mem_region *region;
@@ -1078,12 +1078,12 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 		region->mmap_size += alignment;
 
 	if (flags & KVM_MEM_GUEST_MEMFD) {
-		if (guest_memfd < 0) {
-			u32 guest_memfd_flags = 0;
+		if (gmem_fd < 0) {
+			u32 gmem_flags = 0;
 
-			TEST_ASSERT(!guest_memfd_offset,
+			TEST_ASSERT(!gmem_offset,
 				    "Offset must be zero when creating new guest_memfd");
-			guest_memfd = vm_create_guest_memfd(vm, mem_size, guest_memfd_flags);
+			gmem_fd = vm_create_guest_memfd(vm, mem_size, gmem_flags);
 		} else {
 			/*
 			 * Install a unique fd for each memslot so that the fd
@@ -1091,11 +1091,11 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 			 * needing to track if the fd is owned by the framework
 			 * or by the caller.
 			 */
-			guest_memfd = kvm_dup(guest_memfd);
+			gmem_fd = kvm_dup(gmem_fd);
 		}
 
-		region->region.guest_memfd = guest_memfd;
-		region->region.guest_memfd_offset = guest_memfd_offset;
+		region->region.guest_memfd = gmem_fd;
+		region->region.guest_memfd_offset = gmem_offset;
 	} else {
 		region->region.guest_memfd = -1;
 	}

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 27/45] KVM: selftests: Add support for mmap() on guest_memfd in core library

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Accept gmem_flags in vm_mem_add() to be able to create a guest_memfd within
vm_mem_add().

When vm_mem_add() is used to set up a guest_memfd for a memslot, set up the
provided (or created) gmem_fd as the fd for the user memory region. This
makes it available to be mmap()-ed from just like fds from other memory
sources.

For guest_memfds, mmap() using gmem_offset instead of 0 all the time.

Always use MAP_SHARED if mmap-ing from guest_memfd instead of reading flag
from the configured src_type, which doesn't include guest_memfd.

Add a kvm_slot_to_fd() helper to provide convenient access to the file
descriptor of a memslot.

Update existing callers of vm_mem_add() to pass 0 for gmem_flags to
preserve existing behavior.

Signed-off-by: Sean Christopherson <seanjc@google.com>
[mmap() with gmem_offset, and always with MAP_SHARED.]
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/include/kvm_util.h     |  7 +++++-
 tools/testing/selftests/kvm/lib/kvm_util.c         | 28 ++++++++++++----------
 .../kvm/x86/private_mem_conversions_test.c         |  2 +-
 3 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index cf49a84de02e8..a091c495442a1 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -700,7 +700,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 				 gpa_t gpa, u32 slot, u64 npages, u32 flags);
 void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 		gpa_t gpa, u32 slot, u64 npages, u32 flags,
-		int gmem_fd, u64 gmem_offset);
+		int gmem_fd, u64 gmem_offset, u64 gmem_flags);
 
 #ifndef vm_arch_has_protected_memory
 static inline bool vm_arch_has_protected_memory(struct kvm_vm *vm)
@@ -732,6 +732,11 @@ void *addr_gva2hva(struct kvm_vm *vm, gva_t gva);
 gpa_t addr_hva2gpa(struct kvm_vm *vm, void *hva);
 void *addr_gpa2alias(struct kvm_vm *vm, gpa_t gpa);
 
+static inline int kvm_slot_to_fd(struct kvm_vm *vm, u32 slot)
+{
+	return memslot2region(vm, slot)->fd;
+}
+
 #ifndef vcpu_arch_put_guest
 #define vcpu_arch_put_guest(mem, val) do { (mem) = (val); } while (0)
 #endif
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index af501a27211a2..08d0bbcd421ea 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1002,12 +1002,14 @@ void vm_set_user_memory_region2(struct kvm_vm *vm, u32 slot, u32 flags,
 /* FIXME: This thing needs to be ripped apart and rewritten. */
 void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 		gpa_t gpa, u32 slot, u64 npages, u32 flags,
-		int gmem_fd, u64 gmem_offset)
+		int gmem_fd, u64 gmem_offset, u64 gmem_flags)
 {
 	int ret;
 	struct userspace_mem_region *region;
 	size_t backing_src_pagesz = get_backing_src_pagesz(src_type);
+	int mmap_flags = vm_mem_backing_src_alias(src_type)->flag;
 	size_t mem_size = npages * vm->page_size;
+	off_t mmap_offset = 0;
 	size_t alignment = 1;
 
 	TEST_REQUIRE_SET_USER_MEMORY_REGION2();
@@ -1079,8 +1081,6 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 
 	if (flags & KVM_MEM_GUEST_MEMFD) {
 		if (gmem_fd < 0) {
-			u32 gmem_flags = 0;
-
 			TEST_ASSERT(!gmem_offset,
 				    "Offset must be zero when creating new guest_memfd");
 			gmem_fd = vm_create_guest_memfd(vm, mem_size, gmem_flags);
@@ -1101,13 +1101,17 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 	}
 
 	region->fd = -1;
-	if (backing_src_is_shared(src_type))
+	if (flags & KVM_MEM_GUEST_MEMFD && gmem_flags & GUEST_MEMFD_FLAG_MMAP) {
+		region->fd = kvm_dup(gmem_fd);
+		mmap_flags = MAP_SHARED;
+		mmap_offset = gmem_offset;
+	} else if (backing_src_is_shared(src_type)) {
 		region->fd = kvm_memfd_alloc(region->mmap_size,
 					     src_type == VM_MEM_SRC_SHARED_HUGETLB);
+	}
 
-	region->mmap_start = kvm_mmap(region->mmap_size, PROT_READ | PROT_WRITE,
-				      vm_mem_backing_src_alias(src_type)->flag,
-				      region->fd);
+	region->mmap_start = __kvm_mmap(region->mmap_size, PROT_READ | PROT_WRITE,
+					mmap_flags, region->fd, mmap_offset);
 
 	TEST_ASSERT(!is_backing_src_hugetlb(src_type) ||
 		    region->mmap_start == align_ptr_up(region->mmap_start, backing_src_pagesz),
@@ -1153,10 +1157,10 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 
 	/* If shared memory, create an alias. */
 	if (region->fd >= 0) {
-		region->mmap_alias = kvm_mmap(region->mmap_size,
-					      PROT_READ | PROT_WRITE,
-					      vm_mem_backing_src_alias(src_type)->flag,
-					      region->fd);
+		region->mmap_alias = __kvm_mmap(region->mmap_size,
+						PROT_READ | PROT_WRITE,
+						mmap_flags, region->fd,
+						mmap_offset);
 
 		/* Align host alias address */
 		region->host_alias = align_ptr_up(region->mmap_alias, alignment);
@@ -1167,7 +1171,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 				 enum vm_mem_backing_src_type src_type,
 				 gpa_t gpa, u32 slot, u64 npages, u32 flags)
 {
-	vm_mem_add(vm, src_type, gpa, slot, npages, flags, -1, 0);
+	vm_mem_add(vm, src_type, gpa, slot, npages, flags, -1, 0, 0);
 }
 
 /*
diff --git a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
index 3aa0673f79f33..f3de2a4ab0551 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -399,7 +399,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_v
 	for (i = 0; i < nr_memslots; i++)
 		vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i,
 			   BASE_DATA_SLOT + i, slot_size / vm->page_size,
-			   KVM_MEM_GUEST_MEMFD, memfd, slot_size * i);
+			   KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, 0);
 
 	for (i = 0; i < nr_vcpus; i++) {
 		gpa_t gpa =  BASE_DATA_GPA + i * per_cpu_size;

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 28/45] KVM: selftests: Add selftests global for guest memory attributes capability

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Add a global variable, kvm_has_gmem_attributes, to make the result of
checking for KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES available to all tests.

kvm_has_gmem_attributes is true if guest_memfd tracks memory attributes, as
opposed to VM-level tracking.

This global variable is synced to the guest for testing convenience, to
avoid introducing subtle bugs when host/guest state is desynced.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/include/test_util.h | 2 ++
 tools/testing/selftests/kvm/lib/kvm_util.c      | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index a6a3e16578959..d5825211f2727 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -116,6 +116,8 @@ struct kvm_random_state {
 extern u32 kvm_random_seed;
 extern struct kvm_random_state kvm_rng;
 
+extern bool kvm_has_gmem_attributes;
+
 struct kvm_random_state new_kvm_random_state(u32 seed);
 u32 kvm_random_u32(struct kvm_random_state *state);
 
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 08d0bbcd421ea..cd468b2bb8343 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -32,6 +32,8 @@ static void kvm_seed_rng(u32 seed)
 	kvm_rng = new_kvm_random_state(kvm_random_seed);
 }
 
+bool kvm_has_gmem_attributes;
+
 static size_t vcpu_mmap_sz(void);
 
 int __open_path_or_exit(const char *path, int flags, const char *enoent_help)
@@ -527,6 +529,7 @@ struct kvm_vm *__vm_create(struct vm_shape shape, u32 nr_runnable_vcpus,
 		kvm_seed_rng(kvm_random_seed);
 
 	sync_global_to_guest(vm, kvm_rng);
+	sync_global_to_guest(vm, kvm_has_gmem_attributes);
 
 	kvm_arch_vm_post_create(vm, nr_runnable_vcpus);
 
@@ -2311,6 +2314,8 @@ void __attribute((constructor)) kvm_selftest_init(void)
 	srandom(time(0));
 	kvm_seed_rng(random());
 
+	kvm_has_gmem_attributes = kvm_has_cap(KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES);
+
 	kvm_selftest_arch_init();
 }
 

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 29/45] KVM: selftests: Add helpers for calling ioctls on guest_memfd

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Add helper functions to kvm_util.h to support calling ioctls, specifically
KVM_SET_MEMORY_ATTRIBUTES2, on a guest_memfd file descriptor.

Introduce gmem_ioctl() and __gmem_ioctl() macros, modeled after the
existing vm_ioctl() helpers, to provide a standard way to call ioctls
on a guest_memfd.

Add gmem_set_memory_attributes() and its derivatives (gmem_set_private(),
gmem_set_shared()) to set memory attributes on a guest_memfd region.
Also provide "__" variants that return the ioctl error code instead of
aborting the test. These helpers will be used by upcoming guest_memfd
tests.

To avoid code duplication, factor out the check for supported memory
attributes into a new macro, TEST_ASSERT_SUPPORTED_ATTRIBUTES, and use
it in both the existing vm_set_memory_attributes() and the new
gmem_set_memory_attributes() helpers.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/include/kvm_util.h | 94 +++++++++++++++++++++++---
 1 file changed, 86 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index a091c495442a1..575032e9791d2 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -392,6 +392,16 @@ static __always_inline void static_assert_is_vcpu(struct kvm_vcpu *vcpu) { }
 	__TEST_ASSERT_VM_VCPU_IOCTL(!ret, #cmd, ret, (vcpu)->vm);	\
 })
 
+#define __gmem_ioctl(gmem_fd, cmd, arg)				\
+	kvm_do_ioctl(gmem_fd, cmd, arg)
+
+#define gmem_ioctl(gmem_fd, cmd, arg)				\
+({								\
+	int ret = __gmem_ioctl(gmem_fd, cmd, arg);		\
+								\
+	TEST_ASSERT(!ret, __KVM_IOCTL_ERROR(#cmd, ret));	\
+})
+
 /*
  * Looks up and returns the value corresponding to the capability
  * (KVM_CAP_*) given by cap.
@@ -418,8 +428,16 @@ static inline void vm_enable_cap(struct kvm_vm *vm, u32 cap, u64 arg0)
 	vm_ioctl(vm, KVM_ENABLE_CAP, &enable_cap);
 }
 
+/*
+ * KVM_SET_MEMORY_ATTRIBUTES{,2} overwrites _all_ attributes.  These
+ * flows need significant enhancements to support multiple attributes.
+ */
+#define TEST_ASSERT_SUPPORTED_ATTRIBUTES(attributes)				\
+	TEST_ASSERT(!(attributes) || (attributes) == KVM_MEMORY_ATTRIBUTE_PRIVATE,	\
+		    "Update me to support multiple attributes!")
+
 static inline void vm_set_memory_attributes(struct kvm_vm *vm, gpa_t gpa,
-					    u64 size, u64 attributes)
+					    size_t size, u64 attributes)
 {
 	struct kvm_memory_attributes attr = {
 		.attributes = attributes,
@@ -428,17 +446,11 @@ static inline void vm_set_memory_attributes(struct kvm_vm *vm, gpa_t gpa,
 		.flags = 0,
 	};
 
-	/*
-	 * KVM_SET_MEMORY_ATTRIBUTES overwrites _all_ attributes.  These flows
-	 * need significant enhancements to support multiple attributes.
-	 */
-	TEST_ASSERT(!attributes || attributes == KVM_MEMORY_ATTRIBUTE_PRIVATE,
-		    "Update me to support multiple attributes!");
+	TEST_ASSERT_SUPPORTED_ATTRIBUTES(attributes);
 
 	vm_ioctl(vm, KVM_SET_MEMORY_ATTRIBUTES, &attr);
 }
 
-
 static inline void vm_mem_set_private(struct kvm_vm *vm, gpa_t gpa,
 				      u64 size)
 {
@@ -451,6 +463,72 @@ static inline void vm_mem_set_shared(struct kvm_vm *vm, gpa_t gpa,
 	vm_set_memory_attributes(vm, gpa, size, 0);
 }
 
+static inline int __gmem_set_memory_attributes(int fd, u64 offset,
+					       size_t size, u64 attributes,
+					       u64 *error_offset)
+{
+	struct kvm_memory_attributes2 attr = {
+		.attributes = attributes,
+		.offset = offset,
+		.size = size,
+		.flags = 0,
+		.error_offset = 0,
+	};
+	int r;
+
+	r = __gmem_ioctl(fd, KVM_SET_MEMORY_ATTRIBUTES2, &attr);
+
+	/* Copy error_offset regardless of r so caller can check. */
+	if (error_offset)
+		*error_offset = attr.error_offset;
+
+	return r;
+}
+
+static inline int __gmem_set_private(int fd, u64 offset, size_t size,
+				     u64 *error_offset)
+{
+	return __gmem_set_memory_attributes(fd, offset, size,
+					    KVM_MEMORY_ATTRIBUTE_PRIVATE,
+					    error_offset);
+}
+
+static inline int __gmem_set_shared(int fd, u64 offset, size_t size,
+				    u64 *error_offset)
+{
+	return __gmem_set_memory_attributes(fd, offset, size, 0,
+					    error_offset);
+}
+
+static inline void gmem_set_memory_attributes(int fd, u64 offset,
+					      size_t size, u64 attributes)
+{
+	struct kvm_memory_attributes2 attr = {
+		.attributes = attributes,
+		.offset = offset,
+		.size = size,
+		.flags = 0,
+	};
+
+	TEST_ASSERT_SUPPORTED_ATTRIBUTES(attributes);
+
+	__TEST_REQUIRE(kvm_check_cap(KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES) > 0,
+		       "No valid attributes for guest_memfd ioctl!");
+
+	gmem_ioctl(fd, KVM_SET_MEMORY_ATTRIBUTES2, &attr);
+}
+
+static inline void gmem_set_private(int fd, u64 offset, size_t size)
+{
+	gmem_set_memory_attributes(fd, offset, size,
+				   KVM_MEMORY_ATTRIBUTE_PRIVATE);
+}
+
+static inline void gmem_set_shared(int fd, u64 offset, size_t size)
+{
+	gmem_set_memory_attributes(fd, offset, size, 0);
+}
+
 void vm_guest_mem_fallocate(struct kvm_vm *vm, gpa_t gpa, u64 size,
 			    bool punch_hole);
 

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 30/45] KVM: selftests: Test basic single-page conversion flow

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Add a selftest for the guest_memfd memory attribute conversion ioctls.
The test starts the guest_memfd as all-private (the default state), and
verifies the basic flow of converting a single page to shared and then back
to private.

Add infrastructure that supports extensions to other conversion flow
tests. This infrastructure will be used in upcoming patches for other
conversion tests.

Add test as an x86-specific test since guest_memfd's testing
vehicle (KVM_X86_SW_PROTECTED_VM) is x86-specific.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>

---
v10: Updated __GMEM_CONVERSION_TEST macro to avoid potential macro argument
     reuse
---
 tools/testing/selftests/kvm/Makefile.kvm           |   1 +
 .../kvm/x86/guest_memfd_conversions_test.c         | 200 +++++++++++++++++++++
 2 files changed, 201 insertions(+)

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 96bab7002d39e..239bc61ea384f 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -155,6 +155,7 @@ TEST_GEN_PROGS_x86 += x86/max_vcpuid_cap_test
 TEST_GEN_PROGS_x86 += x86/triple_fault_event_test
 TEST_GEN_PROGS_x86 += x86/recalc_apic_map_test
 TEST_GEN_PROGS_x86 += x86/aperfmperf_test
+TEST_GEN_PROGS_x86 += x86/guest_memfd_conversions_test
 TEST_GEN_PROGS_x86 += access_tracking_perf_test
 TEST_GEN_PROGS_x86 += coalesced_io_test
 TEST_GEN_PROGS_x86 += dirty_log_perf_test
diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
new file mode 100644
index 0000000000000..77f95d49349ce
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2024, Google LLC.
+ */
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <linux/align.h>
+#include <linux/kvm.h>
+#include <linux/sizes.h>
+
+#include "kvm_util.h"
+#include "kselftest_harness.h"
+#include "test_util.h"
+#include "ucall_common.h"
+
+FIXTURE(gmem_conversions) {
+	struct kvm_vcpu *vcpu;
+	int gmem_fd;
+	/* HVA of the first byte of the memory mmap()-ed from gmem_fd. */
+	char *mem;
+};
+
+typedef FIXTURE_DATA(gmem_conversions) test_data_t;
+
+FIXTURE_SETUP(gmem_conversions) { }
+
+static size_t page_size;
+
+static void guest_do_rmw(void);
+#define GUEST_MEMFD_SHARING_TEST_GVA 0x90000000ULL
+
+/*
+ * Defer setup until the individual test is invoked so that tests can specify
+ * the number of pages and flags for the guest_memfd instance.
+ */
+static void gmem_conversions_do_setup(test_data_t *t, int nr_pages,
+				      int gmem_flags)
+{
+	const struct vm_shape shape = {
+		.mode = VM_MODE_DEFAULT,
+		.type = KVM_X86_SW_PROTECTED_VM,
+	};
+	/*
+	 * Use high GPA above APIC_DEFAULT_PHYS_BASE to avoid clashing with
+	 * APIC_DEFAULT_PHYS_BASE.
+	 */
+	const gpa_t gpa = SZ_4G;
+	const u32 slot = 1;
+	struct kvm_vm *vm;
+
+	vm = __vm_create_shape_with_one_vcpu(shape, &t->vcpu, nr_pages, guest_do_rmw);
+
+	vm_mem_add(vm, VM_MEM_SRC_SHMEM, gpa, slot, nr_pages,
+		   KVM_MEM_GUEST_MEMFD, -1, 0, gmem_flags);
+
+	t->gmem_fd = kvm_slot_to_fd(vm, slot);
+	t->mem = addr_gpa2hva(vm, gpa);
+	virt_map(vm, GUEST_MEMFD_SHARING_TEST_GVA, gpa, nr_pages);
+}
+
+static void gmem_conversions_do_teardown(test_data_t *t)
+{
+	/* No need to close gmem_fd, it's owned by the VM structure. */
+	kvm_vm_free(t->vcpu->vm);
+}
+
+FIXTURE_TEARDOWN(gmem_conversions)
+{
+	gmem_conversions_do_teardown(self);
+}
+
+/*
+ * In these test definition macros, __nr_pages and nr_pages is used to set up
+ * the total number of pages in the guest_memfd under test. This will be
+ * available in the test definitions as nr_pages.
+ */
+
+#define __GMEM_CONVERSION_TEST(test, __nr_pages, flags)				\
+static void __gmem_conversions_##test(test_data_t *t, int nr_pages);		\
+										\
+TEST_F(gmem_conversions, test)							\
+{										\
+	const int nr = (__nr_pages);						\
+										\
+	gmem_conversions_do_setup(self, nr, flags);				\
+	__gmem_conversions_##test(self, nr);					\
+}										\
+static void __gmem_conversions_##test(test_data_t *t, int nr_pages)		\
+
+#define GMEM_CONVERSION_TEST(test, __nr_pages, flags)				\
+	__GMEM_CONVERSION_TEST(test, __nr_pages, (flags) | GUEST_MEMFD_FLAG_MMAP)
+
+#define __GMEM_CONVERSION_TEST_INIT_PRIVATE(test, __nr_pages)			\
+	GMEM_CONVERSION_TEST(test, __nr_pages, 0)
+
+#define GMEM_CONVERSION_TEST_INIT_PRIVATE(test)					\
+	__GMEM_CONVERSION_TEST_INIT_PRIVATE(test, 1)
+
+struct guest_check_data {
+	void *mem;
+	char expected_val;
+	char write_val;
+};
+static struct guest_check_data guest_data;
+
+static void guest_do_rmw(void)
+{
+	for (;;) {
+		char *mem = READ_ONCE(guest_data.mem);
+
+		GUEST_ASSERT_EQ(READ_ONCE(*mem), READ_ONCE(guest_data.expected_val));
+		WRITE_ONCE(*mem, READ_ONCE(guest_data.write_val));
+
+		GUEST_SYNC(0);
+	}
+}
+
+static void run_guest_do_rmw(struct kvm_vcpu *vcpu, u64 pgoff,
+			     char expected_val, char write_val)
+{
+	struct ucall uc;
+	int r;
+
+	guest_data.mem = (void *)GUEST_MEMFD_SHARING_TEST_GVA + pgoff * page_size;
+	guest_data.expected_val = expected_val;
+	guest_data.write_val = write_val;
+	sync_global_to_guest(vcpu->vm, guest_data);
+
+	do {
+		r = __vcpu_run(vcpu);
+	} while (r == -1 && errno == EINTR);
+
+	TEST_ASSERT_EQ(r, 0);
+
+	switch (get_ucall(vcpu, &uc)) {
+	case UCALL_ABORT:
+		REPORT_GUEST_ASSERT(uc);
+	case UCALL_SYNC:
+		break;
+	default:
+		TEST_FAIL("Unexpected ucall %lu", uc.cmd);
+	}
+}
+
+static void host_do_rmw(char *mem, u64 pgoff, char expected_val,
+			char write_val)
+{
+	TEST_ASSERT_EQ(READ_ONCE(mem[pgoff * page_size]), expected_val);
+	WRITE_ONCE(mem[pgoff * page_size], write_val);
+}
+
+static void test_private(test_data_t *t, u64 pgoff, char starting_val,
+			 char write_val)
+{
+	TEST_EXPECT_SIGBUS(WRITE_ONCE(t->mem[pgoff * page_size], write_val));
+	run_guest_do_rmw(t->vcpu, pgoff, starting_val, write_val);
+	TEST_EXPECT_SIGBUS(READ_ONCE(t->mem[pgoff * page_size]));
+}
+
+static void test_convert_to_private(test_data_t *t, u64 pgoff,
+				    char starting_val, char write_val)
+{
+	gmem_set_private(t->gmem_fd, pgoff * page_size, page_size);
+	test_private(t, pgoff, starting_val, write_val);
+}
+
+static void test_shared(test_data_t *t, u64 pgoff, char starting_val,
+			char host_write_val, char write_val)
+{
+	host_do_rmw(t->mem, pgoff, starting_val, host_write_val);
+	run_guest_do_rmw(t->vcpu, pgoff, host_write_val, write_val);
+	TEST_ASSERT_EQ(READ_ONCE(t->mem[pgoff * page_size]), write_val);
+}
+
+static void test_convert_to_shared(test_data_t *t, u64 pgoff,
+				   char starting_val, char host_write_val,
+				   char write_val)
+{
+	gmem_set_shared(t->gmem_fd, pgoff * page_size, page_size);
+	test_shared(t, pgoff, starting_val, host_write_val, write_val);
+}
+
+GMEM_CONVERSION_TEST_INIT_PRIVATE(init_private)
+{
+	test_private(t, 0, 0, 'A');
+	test_convert_to_shared(t, 0, 'A', 'B', 'C');
+	test_convert_to_private(t, 0, 'C', 'E');
+}
+
+int main(int argc, char *argv[])
+{
+	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
+	TEST_REQUIRE(kvm_check_cap(KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES) &
+		     KVM_MEMORY_ATTRIBUTE_PRIVATE);
+
+	page_size = getpagesize();
+
+	return test_harness_run(argc, argv);
+}

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 31/45] KVM: selftests: Test conversion flow when INIT_SHARED

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Add a test case to verify that conversions between private and shared
memory work correctly when the memory is initially created as shared.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../selftests/kvm/x86/guest_memfd_conversions_test.c        | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index 77f95d49349ce..4c20d3d8e9349 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -97,6 +97,12 @@ static void __gmem_conversions_##test(test_data_t *t, int nr_pages)		\
 #define GMEM_CONVERSION_TEST_INIT_PRIVATE(test)					\
 	__GMEM_CONVERSION_TEST_INIT_PRIVATE(test, 1)
 
+#define __GMEM_CONVERSION_TEST_INIT_SHARED(test, __nr_pages)			\
+	GMEM_CONVERSION_TEST(test, __nr_pages, GUEST_MEMFD_FLAG_INIT_SHARED)
+
+#define GMEM_CONVERSION_TEST_INIT_SHARED(test)					\
+	__GMEM_CONVERSION_TEST_INIT_SHARED(test, 1)
+
 struct guest_check_data {
 	void *mem;
 	char expected_val;
@@ -188,6 +194,13 @@ GMEM_CONVERSION_TEST_INIT_PRIVATE(init_private)
 	test_convert_to_private(t, 0, 'C', 'E');
 }
 
+GMEM_CONVERSION_TEST_INIT_SHARED(init_shared)
+{
+	test_shared(t, 0, 0, 'A', 'B');
+	test_convert_to_private(t, 0, 'B', 'C');
+	test_convert_to_shared(t, 0, 'C', 'D', 'E');
+}
+
 int main(int argc, char *argv[])
 {
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 32/45] KVM: selftests: Test conversion precision in guest_memfd

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

The existing guest_memfd conversion tests only use single-page memory
regions. This provides no coverage for multi-page guest_memfd objects,
specifically whether KVM correctly handles the page index for conversion
operations. An incorrect implementation could, for example, always operate
on the first page regardless of the index provided.

Add a new test case to verify that conversions between private and shared
memory correctly target the specified page within a multi-page guest_memfd.

This test also verifies the precision of memory conversions by converting a
single page and then iterating through all other pages to ensure they
remain in their original state.

To support this test, add a new GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED
macro that handles setting up and tearing down the VM for each page
iteration. The teardown logic is adjusted to prevent a double-free in this
new scenario.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>

---

v10: Update macro GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED to avoid
     potential macro argument reuse
---
 .../kvm/x86/guest_memfd_conversions_test.c         | 67 ++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index 4c20d3d8e9349..a8d89df53e46d 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -61,8 +61,13 @@ static void gmem_conversions_do_setup(test_data_t *t, int nr_pages,
 
 static void gmem_conversions_do_teardown(test_data_t *t)
 {
+	/* Use NULL to avoid second free in FIXTURE_TEARDOWN (multipage tests). */
+	if (!t->vcpu)
+		return;
+
 	/* No need to close gmem_fd, it's owned by the VM structure. */
 	kvm_vm_free(t->vcpu->vm);
+	t->vcpu = NULL;
 }
 
 FIXTURE_TEARDOWN(gmem_conversions)
@@ -103,6 +108,30 @@ static void __gmem_conversions_##test(test_data_t *t, int nr_pages)		\
 #define GMEM_CONVERSION_TEST_INIT_SHARED(test)					\
 	__GMEM_CONVERSION_TEST_INIT_SHARED(test, 1)
 
+/*
+ * Repeats test over nr_pages in a guest_memfd of size nr_pages, providing each
+ * test iteration with test_page, the index of the page under test in
+ * guest_memfd. test_page takes values 0..(nr_pages - 1) inclusive.
+ */
+#define GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(test, __nr_pages)		\
+static void __gmem_conversions_multipage_##test(test_data_t *t, int nr_pages,	\
+						const int test_page);		\
+										\
+TEST_F(gmem_conversions, test)							\
+{										\
+	const u64 flags = GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_INIT_SHARED; \
+	const int nr = (__nr_pages);						\
+	int i;									\
+										\
+	for (i = 0; i < nr; ++i) {						\
+		gmem_conversions_do_setup(self, nr, flags);			\
+		__gmem_conversions_multipage_##test(self, nr, i);		\
+		gmem_conversions_do_teardown(self);				\
+	}									\
+}										\
+static void __gmem_conversions_multipage_##test(test_data_t *t, int nr_pages,	\
+						const int test_page)
+
 struct guest_check_data {
 	void *mem;
 	char expected_val;
@@ -201,6 +230,44 @@ GMEM_CONVERSION_TEST_INIT_SHARED(init_shared)
 	test_convert_to_shared(t, 0, 'C', 'D', 'E');
 }
 
+GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(indexing, 4)
+{
+	int i;
+
+	/* Get a char that varies with both i and n. */
+#define combine(x, n) (((x) << 4) + (n))
+#define i_(n) (combine(i, n))
+#define t_(n) (combine(test_page, n))
+
+	/*
+	 * Start with the highest index, to catch any errors when, perhaps, the
+	 * first page is returned even for the last index.
+	 */
+	for (i = nr_pages - 1; i >= 0; --i)
+		test_shared(t, i, 0, i_(0), i_(2));
+
+	test_convert_to_private(t, test_page, t_(2), t_(3));
+
+	for (i = 0; i < nr_pages; ++i) {
+		if (i == test_page)
+			test_private(t, test_page, t_(3), t_(4));
+		else
+			test_shared(t, i, i_(2), i_(3), i_(4));
+	}
+
+	test_convert_to_shared(t, test_page, t_(4), t_(5), t_(6));
+
+	for (i = 0; i < nr_pages; ++i) {
+		char expected = i == test_page ? t_(6) : i_(4);
+
+		test_shared(t, i, expected, i_(7), i_(8));
+	}
+
+#undef t_
+#undef i_
+#undef combine
+}
+
 int main(int argc, char *argv[])
 {
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 33/45] KVM: selftests: Test conversion before allocation

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Add two test cases to the guest_memfd conversions selftest to cover
the scenario where a conversion is requested before any memory has been
allocated in the guest_memfd region.

The KVM_SET_MEMORY_ATTRIBUTES2 ioctl can be called on a memory region at
any time. If the guest had not yet faulted in any pages for that region,
the kernel must record the conversion request and apply the requested state
when the pages are eventually allocated.

The new tests cover both conversion directions.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../selftests/kvm/x86/guest_memfd_conversions_test.c       | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index a8d89df53e46d..f46f1530a94b9 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -268,6 +268,20 @@ GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(indexing, 4)
 #undef combine
 }
 
+/*
+ * Test that even if there are no folios yet, conversion requests are recorded
+ * in guest_memfd.
+ */
+GMEM_CONVERSION_TEST_INIT_SHARED(before_allocation_shared)
+{
+	test_convert_to_private(t, 0, 0, 'A');
+}
+
+GMEM_CONVERSION_TEST_INIT_PRIVATE(before_allocation_private)
+{
+	test_convert_to_shared(t, 0, 0, 'A', 'B');
+}
+
 int main(int argc, char *argv[])
 {
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 34/45] KVM: selftests: Convert with allocated folios in different layouts

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Add a guest_memfd selftest to verify that memory conversions work
correctly with allocated folios in different layouts.

By iterating through which pages are initially faulted, the test covers
various layouts of contiguous allocated and unallocated regions, exercising
conversion with different range layouts.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../kvm/x86/guest_memfd_conversions_test.c         | 30 ++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index f46f1530a94b9..acdff2d154046 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -282,6 +282,36 @@ GMEM_CONVERSION_TEST_INIT_PRIVATE(before_allocation_private)
 	test_convert_to_shared(t, 0, 0, 'A', 'B');
 }
 
+/*
+ * Test that when some of the folios in the conversion range are allocated,
+ * conversion requests are handled correctly in guest_memfd.  Vary the ranges
+ * allocated before conversion, using test_page, to cover various layouts of
+ * contiguous allocated and unallocated regions.
+ */
+GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(unallocated_folios, 8)
+{
+	const int second_page_to_fault = 4;
+	int i;
+
+	/*
+	 * Fault 2 of the pages to test filemap range operations except when
+	 * test_page == second_page_to_fault.
+	 */
+	host_do_rmw(t->mem, test_page, 0, 'A');
+	if (test_page != second_page_to_fault)
+		host_do_rmw(t->mem, second_page_to_fault, 0, 'A');
+
+	gmem_set_private(t->gmem_fd, 0, nr_pages * page_size);
+	for (i = 0; i < nr_pages; ++i) {
+		char expected = (i == test_page || i == second_page_to_fault) ? 'A' : 0;
+
+		test_private(t, i, expected, 'B');
+	}
+
+	for (i = 0; i < nr_pages; ++i)
+		test_convert_to_shared(t, i, 'B', 'C', 'D');
+}
+
 int main(int argc, char *argv[])
 {
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 35/45] KVM: selftests: Test that truncation does not change shared/private status

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Add a test to verify that deallocating a page in a guest memfd region via
fallocate() with FALLOC_FL_PUNCH_HOLE does not alter the shared or private
status of the corresponding memory range.

When a page backing a guest memfd mapping is deallocated, e.g., by punching
a hole or truncating the file, and then subsequently faulted back in, the
new page must inherit the correct shared/private status tracked by
guest_memfd.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../selftests/kvm/x86/guest_memfd_conversions_test.c       | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index acdff2d154046..b7a54d2a90928 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -10,6 +10,7 @@
 #include <linux/sizes.h>
 
 #include "kvm_util.h"
+#include "kvm_syscalls.h"
 #include "kselftest_harness.h"
 #include "test_util.h"
 #include "ucall_common.h"
@@ -312,6 +313,19 @@ GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(unallocated_folios, 8)
 		test_convert_to_shared(t, i, 'B', 'C', 'D');
 }
 
+/* Truncation should not affect shared/private status. */
+GMEM_CONVERSION_TEST_INIT_SHARED(truncate)
+{
+	host_do_rmw(t->mem, 0, 0, 'A');
+	kvm_fallocate(t->gmem_fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+	host_do_rmw(t->mem, 0, 0, 'A');
+
+	test_convert_to_private(t, 0, 'A', 'B');
+
+	kvm_fallocate(t->gmem_fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+	test_private(t, 0, 0, 'A');
+}
+
 int main(int argc, char *argv[])
 {
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 36/45] KVM: selftests: Test that shared/private status is consistent across processes

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Add a test to verify that a guest_memfd's shared/private status is
consistent across processes, and that any shared pages previously mapped in
any process are unmapped from all processes.

The test forks a child process after creating the shared guest_memfd
region so that the second process exists alongside the main process for the
entire test.

The processes then take turns to access memory to check that the
shared/private status is consistent across processes.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../kvm/x86/guest_memfd_conversions_test.c         | 118 +++++++++++++++++++++
 1 file changed, 118 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index b7a54d2a90928..a972a09c5c6e5 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -2,7 +2,9 @@
 /*
  * Copyright (c) 2024, Google LLC.
  */
+#include <pthread.h>
 #include <sys/mman.h>
+#include <time.h>
 #include <unistd.h>
 
 #include <linux/align.h>
@@ -326,6 +328,122 @@ GMEM_CONVERSION_TEST_INIT_SHARED(truncate)
 	test_private(t, 0, 0, 'A');
 }
 
+/* Test that shared/private memory protections work and are seen from any process. */
+GMEM_CONVERSION_TEST_INIT_SHARED(forked_accesses)
+{
+	enum test_state {
+		STATE_INIT,
+		STATE_CHECK_SHARED,
+		STATE_DONE_CHECKING_SHARED,
+		STATE_CHECK_PRIVATE,
+		STATE_DONE_CHECKING_PRIVATE,
+	};
+
+	struct sync_state {
+		pthread_mutex_t mutex;
+		pthread_cond_t cond;
+		enum test_state step;
+	} *sync;
+
+	pthread_mutexattr_t mattr;
+	pthread_condattr_t cattr;
+	pid_t child_pid, parent_pid;
+	int status;
+
+	sync = kvm_mmap(sizeof(*sync), PROT_READ | PROT_WRITE,
+			MAP_SHARED | MAP_ANONYMOUS, -1);
+
+	pthread_mutexattr_init(&mattr);
+	pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
+	pthread_mutex_init(&sync->mutex, &mattr);
+	pthread_mutexattr_destroy(&mattr);
+
+	pthread_condattr_init(&cattr);
+	pthread_condattr_setpshared(&cattr, PTHREAD_PROCESS_SHARED);
+	pthread_cond_init(&sync->cond, &cattr);
+	pthread_condattr_destroy(&cattr);
+
+	sync->step = STATE_INIT;
+
+#define TEST_STATE_AWAIT(__state)						\
+	do {									\
+		pthread_mutex_lock(&sync->mutex);				\
+		while (sync->step != (__state)) {				\
+			struct timespec ts, stop;				\
+			int ret;						\
+										\
+			clock_gettime(CLOCK_REALTIME, &ts);			\
+			stop = timespec_add_ns(ts, 100 * 1000000UL);		\
+										\
+			ret = pthread_cond_timedwait(&sync->cond, &sync->mutex, &stop); \
+			if (ret == ETIMEDOUT) {					\
+				bool alive = (child_pid == 0) ?			\
+					     (getppid() == parent_pid) :		\
+					     (waitpid(child_pid, NULL, WNOHANG) == 0); \
+				TEST_ASSERT(alive, "Other process exited prematurely"); \
+			} else {						\
+				TEST_ASSERT(!ret, "pthread_cond_timedwait failed"); \
+			}							\
+		}								\
+		pthread_mutex_unlock(&sync->mutex);				\
+	} while (0)
+
+#define TEST_STATE_SET(__state)							\
+	do {									\
+		pthread_mutex_lock(&sync->mutex);				\
+		sync->step = (__state);						\
+		pthread_cond_broadcast(&sync->cond);				\
+		pthread_mutex_unlock(&sync->mutex);				\
+	} while (0)
+
+	parent_pid = getpid();
+	child_pid = fork();
+	TEST_ASSERT(child_pid != -1, "fork failed");
+
+	if (child_pid == 0) {
+		const char inconsequential = 0xdd;
+
+		TEST_STATE_AWAIT(STATE_CHECK_SHARED);
+
+		/*
+		 * This maps the pages into the child process as well, and tests
+		 * that the conversion process will unmap the guest_memfd memory
+		 * from all processes.
+		 */
+		host_do_rmw(t->mem, 0, 0xB, 0xC);
+
+		TEST_STATE_SET(STATE_DONE_CHECKING_SHARED);
+		TEST_STATE_AWAIT(STATE_CHECK_PRIVATE);
+
+		TEST_EXPECT_SIGBUS(READ_ONCE(t->mem[0]));
+		TEST_EXPECT_SIGBUS(WRITE_ONCE(t->mem[0], inconsequential));
+
+		TEST_STATE_SET(STATE_DONE_CHECKING_PRIVATE);
+		exit(0);
+	}
+
+	test_shared(t, 0, 0, 0xA, 0xB);
+
+	TEST_STATE_SET(STATE_CHECK_SHARED);
+	TEST_STATE_AWAIT(STATE_DONE_CHECKING_SHARED);
+
+	test_convert_to_private(t, 0, 0xC, 0xD);
+
+	TEST_STATE_SET(STATE_CHECK_PRIVATE);
+	TEST_STATE_AWAIT(STATE_DONE_CHECKING_PRIVATE);
+
+	TEST_ASSERT_EQ(waitpid(child_pid, &status, 0), child_pid);
+	TEST_ASSERT(WIFEXITED(status) && WEXITSTATUS(status) == 0,
+		    "Child exited with unexpected status");
+
+	pthread_mutex_destroy(&sync->mutex);
+	pthread_cond_destroy(&sync->cond);
+	kvm_munmap(sync, sizeof(*sync));
+
+#undef TEST_STATE_SET
+#undef TEST_STATE_AWAIT
+}
+
 int main(int argc, char *argv[])
 {
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 37/45] KVM: selftests: Add helpers to pin pages with CONFIG_GUP_TEST

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Add helper functions to allow KVM selftests to pin memory using
CONFIG_GUP_TEST. This is useful for creating test scenarios where some page
has an increased refcount, such as when testing guest_memfd in-place
conversion.

The helpers open /sys/kernel/debug/gup_test and invoke the
PIN_LONGTERM_TEST_START and PIN_LONGTERM_TEST_STOP ioctls. Since this
functionality depends on the kernel being built with CONFIG_GUP_TEST,
provide stub implementations that trigger a test failure if the
configuration is missing.

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/include/kvm_util.h |  3 +++
 tools/testing/selftests/kvm/lib/kvm_util.c     | 25 +++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 575032e9791d2..3cfe243d7c8b0 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -1206,6 +1206,9 @@ static inline int pin_self_to_any_cpu(void)
 	return pin_task_to_any_cpu(pthread_self());
 }
 
+void pin_pages(void *vaddr, uint64_t size);
+void unpin_pages(void);
+
 void kvm_print_vcpu_pinning_help(void);
 void kvm_parse_vcpu_pinning(const char *pcpus_string, u32 vcpu_to_pcpu[],
 			    int nr_vcpus);
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index cd468b2bb8343..b1456ed76e27e 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -19,6 +19,8 @@
 #include <unistd.h>
 #include <linux/kernel.h>
 
+#include "../../../../../mm/gup_test.h"
+
 #define KVM_UTIL_MIN_PFN	2
 
 u32 kvm_random_seed;
@@ -645,6 +647,29 @@ int __pin_task_to_cpu(pthread_t task, int cpu)
 	return pthread_setaffinity_np(task, sizeof(cpuset), &cpuset);
 }
 
+static int gup_test_fd = -1;
+
+void pin_pages(void *vaddr, uint64_t size)
+{
+	const struct pin_longterm_test args = {
+		.addr = (uint64_t)vaddr,
+		.size = size,
+		.flags = PIN_LONGTERM_TEST_FLAG_USE_WRITE,
+	};
+
+	gup_test_fd = __open_path_or_exit("/sys/kernel/debug/gup_test", O_RDWR,
+					  "Is CONFIG_GUP_TEST enabled?");
+
+	TEST_ASSERT_EQ(ioctl(gup_test_fd, PIN_LONGTERM_TEST_START, &args), 0);
+}
+
+void unpin_pages(void)
+{
+	TEST_ASSERT_EQ(ioctl(gup_test_fd, PIN_LONGTERM_TEST_STOP), 0);
+
+	kvm_free_fd(gup_test_fd);
+}
+
 static u32 parse_pcpu(const char *cpu_str, const cpu_set_t *allowed_mask)
 {
 	u32 pcpu = atoi_non_negative("CPU number", cpu_str);

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 38/45] KVM: selftests: Test conversion with elevated page refcount

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Add a selftest to verify that converting a shared guest_memfd page to a
private page fails if the page has an elevated reference count.

When KVM converts a shared page to a private one, it expects the page to
have a reference count equal to the reference counts taken by the
filemap. If another kernel subsystem holds a reference to the page, the
conversion must be aborted.

The test asserts that both bulk and single-page conversion attempts
correctly fail with EAGAIN for the pinned page. After the page is unpinned,
the test verifies that subsequent conversions succeed.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../kvm/x86/guest_memfd_conversions_test.c         | 56 ++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index a972a09c5c6e5..e1c84df0f0596 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -444,6 +444,62 @@ GMEM_CONVERSION_TEST_INIT_SHARED(forked_accesses)
 #undef TEST_STATE_AWAIT
 }
 
+static void test_convert_to_private_fails(test_data_t *t, u64 pgoff,
+					  size_t nr_pages,
+					  u64 expected_error_offset)
+{
+	/* +1 to make it anything but expected_error_offset. */
+	u64 error_offset = expected_error_offset + 1;
+	u64 offset = pgoff * page_size;
+	int ret;
+
+	do {
+		ret = __gmem_set_private(t->gmem_fd, offset,
+					 nr_pages * page_size, &error_offset);
+	} while (ret == -1 && errno == EINTR);
+	TEST_ASSERT(ret == -1 && errno == EAGAIN,
+		    "Wanted EAGAIN on page %lu, got %d (ret = %d)", pgoff,
+		    errno, ret);
+	TEST_ASSERT_EQ(error_offset, expected_error_offset);
+}
+
+GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(elevated_refcount, 4)
+{
+	int i;
+
+	pin_pages(t->mem + test_page * page_size, page_size);
+
+	for (i = 0; i < nr_pages; i++)
+		test_shared(t, i, 0, 'A', 'B');
+
+	/*
+	 * Converting in bulk should fail as long any page in the range has
+	 * unexpected refcounts.
+	 */
+	test_convert_to_private_fails(t, 0, nr_pages, test_page * page_size);
+
+	for (i = 0; i < nr_pages; i++) {
+		/*
+		 * Converting page-wise should also fail as long any page in the
+		 * range has unexpected refcounts.
+		 */
+		if (i == test_page)
+			test_convert_to_private_fails(t, i, 1, test_page * page_size);
+		else
+			test_convert_to_private(t, i, 'B', 'C');
+	}
+
+	unpin_pages();
+
+	gmem_set_private(t->gmem_fd, 0, nr_pages * page_size);
+
+	for (i = 0; i < nr_pages; i++) {
+		char expected = i == test_page ? 'B' : 'C';
+
+		test_private(t, i, expected, 'D');
+	}
+}
+
 int main(int argc, char *argv[])
 {
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 39/45] KVM: selftests: Reset shared memory after hole-punching

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

private_mem_conversions_test used to reset the shared memory that was used
for the test to an initial pattern at the end of each test iteration. Then,
it would punch out the pages, which would zero memory.

Without in-place conversion, the resetting would write shared memory, and
hole-punching will zero private memory, hence resetting the test to the
state at the beginning of the for loop.

With in-place conversion, resetting writes memory as shared, and
hole-punching zeroes the same physical memory, hence undoing the reset
done before the hole punch.

Move the resetting after the hole-punching, and reset the entire
PER_CPU_DATA_SIZE instead of just the tested range.

With in-place conversion, this zeroes and then resets the same physical
memory. Without in-place conversion, the private memory is zeroed, and the
shared memory is reset to init_p.

This is sufficient since at each test stage, the memory is assumed to start
as shared, and private memory is always assumed to start zeroed. Conversion
zeroes memory, so the future test stages will work as expected.

Fixes: 43f623f350ce1 ("KVM: selftests: Add x86-only selftest for private memory conversions")
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/x86/private_mem_conversions_test.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
index f3de2a4ab0551..cf50e9a332c5b 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -202,15 +202,18 @@ static void guest_test_explicit_conversion(u64 base_gpa, bool do_fallocate)
 		guest_sync_shared(gpa, size, p3, p4);
 		memcmp_g(gpa, p4, size);
 
-		/* Reset the shared memory back to the initial pattern. */
-		memset((void *)gpa, init_p, size);
-
 		/*
 		 * Free (via PUNCH_HOLE) *all* private memory so that the next
 		 * iteration starts from a clean slate, e.g. with respect to
 		 * whether or not there are pages/folios in guest_mem.
 		 */
 		guest_map_shared(base_gpa, PER_CPU_DATA_SIZE, true);
+
+		/*
+		 * Hole-punching above zeroed private memory. Reset shared
+		 * memory in preparation for the next GUEST_STAGE.
+		 */
+		memset((void *)base_gpa, init_p, PER_CPU_DATA_SIZE);
 	}
 }
 

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 40/45] KVM: selftests: Provide function to look up guest_memfd details from gpa

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Introduce a new helper, kvm_gpa_to_guest_memfd(), to find the
guest_memfd-related details of a memory region that contains a given guest
physical address (GPA).

The function returns the file descriptor for the memfd, the offset into
the file that corresponds to the GPA, and the number of bytes remaining
in the region from that GPA.

kvm_gpa_to_guest_memfd() was factored out from vm_guest_mem_fallocate();
refactor vm_guest_mem_fallocate() to use the new helper.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/include/kvm_util.h |  3 +++
 tools/testing/selftests/kvm/lib/kvm_util.c     | 37 ++++++++++++++++----------
 2 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 3cfe243d7c8b0..795c9eb311071 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -428,6 +428,9 @@ static inline void vm_enable_cap(struct kvm_vm *vm, u32 cap, u64 arg0)
 	vm_ioctl(vm, KVM_ENABLE_CAP, &enable_cap);
 }
 
+int kvm_gpa_to_guest_memfd(struct kvm_vm *vm, gpa_t gpa, off_t *fd_offset,
+			   size_t *nr_bytes);
+
 /*
  * KVM_SET_MEMORY_ATTRIBUTES{,2} overwrites _all_ attributes.  These
  * flows need significant enhancements to support multiple attributes.
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index b1456ed76e27e..1188d0a6c0a5f 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1332,27 +1332,20 @@ void vm_guest_mem_fallocate(struct kvm_vm *vm, u64 base, u64 size,
 			    bool punch_hole)
 {
 	const int mode = FALLOC_FL_KEEP_SIZE | (punch_hole ? FALLOC_FL_PUNCH_HOLE : 0);
-	struct userspace_mem_region *region;
 	u64 end = base + size;
-	gpa_t gpa, len;
 	off_t fd_offset;
-	int ret;
+	int fd, ret;
+	size_t len;
+	gpa_t gpa;
 
 	for (gpa = base; gpa < end; gpa += len) {
-		u64 offset;
-
-		region = userspace_mem_region_find(vm, gpa, gpa);
-		TEST_ASSERT(region && region->region.flags & KVM_MEM_GUEST_MEMFD,
-			    "Private memory region not found for GPA 0x%lx", gpa);
+		fd = kvm_gpa_to_guest_memfd(vm, gpa, &fd_offset, &len);
+		len = min(end - gpa, len);
 
-		offset = gpa - region->region.guest_phys_addr;
-		fd_offset = region->region.guest_memfd_offset + offset;
-		len = min_t(u64, end - gpa, region->region.memory_size - offset);
-
-		ret = fallocate(region->region.guest_memfd, mode, fd_offset, len);
+		ret = fallocate(fd, mode, fd_offset, len);
 		TEST_ASSERT(!ret, "fallocate() failed to %s at %lx (len = %lu), fd = %d, mode = %x, offset = %lx",
 			    punch_hole ? "punch hole" : "allocate", gpa, len,
-			    region->region.guest_memfd, mode, fd_offset);
+			    fd, mode, fd_offset);
 	}
 }
 
@@ -1689,6 +1682,22 @@ void *addr_gpa2alias(struct kvm_vm *vm, gpa_t gpa)
 	return (void *) ((uintptr_t) region->host_alias + offset);
 }
 
+int kvm_gpa_to_guest_memfd(struct kvm_vm *vm, gpa_t gpa, off_t *fd_offset,
+			   size_t *nr_bytes)
+{
+	struct userspace_mem_region *region;
+	gpa_t gpa_offset;
+
+	region = userspace_mem_region_find(vm, gpa, gpa);
+	TEST_ASSERT(region && region->region.flags & KVM_MEM_GUEST_MEMFD,
+		    "guest_memfd memory region not found for GPA 0x%lx", gpa);
+
+	gpa_offset = gpa - region->region.guest_phys_addr;
+	*fd_offset = region->region.guest_memfd_offset + gpa_offset;
+	*nr_bytes = region->region.memory_size - gpa_offset;
+	return region->region.guest_memfd;
+}
+
 /* Create an interrupt controller chip for the specified VM. */
 void vm_create_irqchip(struct kvm_vm *vm)
 {

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 41/45] KVM: selftests: Provide common function to set memory attributes

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Introduce vm_mem_set_memory_attributes(), which handles setting of memory
attributes for a range of guest physical addresses, regardless of whether
the attributes should be set via guest_memfd or via the memory attributes
at the VM level.

Refactor existing vm_mem_set_{shared,private} functions to use the new
function. Opportunistically update the size parameter to use size_t instead
of u64.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/include/kvm_util.h | 46 +++++++++++++++++++-------
 1 file changed, 34 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 795c9eb311071..777fa3dbf88d6 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -454,18 +454,6 @@ static inline void vm_set_memory_attributes(struct kvm_vm *vm, gpa_t gpa,
 	vm_ioctl(vm, KVM_SET_MEMORY_ATTRIBUTES, &attr);
 }
 
-static inline void vm_mem_set_private(struct kvm_vm *vm, gpa_t gpa,
-				      u64 size)
-{
-	vm_set_memory_attributes(vm, gpa, size, KVM_MEMORY_ATTRIBUTE_PRIVATE);
-}
-
-static inline void vm_mem_set_shared(struct kvm_vm *vm, gpa_t gpa,
-				     u64 size)
-{
-	vm_set_memory_attributes(vm, gpa, size, 0);
-}
-
 static inline int __gmem_set_memory_attributes(int fd, u64 offset,
 					       size_t size, u64 attributes,
 					       u64 *error_offset)
@@ -532,6 +520,40 @@ static inline void gmem_set_shared(int fd, u64 offset, size_t size)
 	gmem_set_memory_attributes(fd, offset, size, 0);
 }
 
+static inline void vm_mem_set_memory_attributes(struct kvm_vm *vm, gpa_t gpa,
+						size_t size, u64 attrs)
+{
+	if (kvm_has_gmem_attributes) {
+		gpa_t end = gpa + size;
+		off_t fd_offset;
+		gpa_t addr;
+		size_t len;
+		int fd;
+
+		for (addr = gpa; addr < end; addr += len) {
+			fd = kvm_gpa_to_guest_memfd(vm, addr, &fd_offset, &len);
+			len = min(end - addr, len);
+
+			gmem_set_memory_attributes(fd, fd_offset, len, attrs);
+		}
+	} else {
+		vm_set_memory_attributes(vm, gpa, size, attrs);
+	}
+}
+
+static inline void vm_mem_set_private(struct kvm_vm *vm, gpa_t gpa,
+				      size_t size)
+{
+	vm_mem_set_memory_attributes(vm, gpa, size,
+				     KVM_MEMORY_ATTRIBUTE_PRIVATE);
+}
+
+static inline void vm_mem_set_shared(struct kvm_vm *vm, gpa_t gpa,
+				     size_t size)
+{
+	vm_mem_set_memory_attributes(vm, gpa, size, 0);
+}
+
 void vm_guest_mem_fallocate(struct kvm_vm *vm, gpa_t gpa, u64 size,
 			    bool punch_hole);
 

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 42/45] KVM: selftests: Make TEST_EXPECT_SIGBUS thread-safe

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

The TEST_EXPECT_SIGBUS macro is not thread-safe as it uses a global
sigjmp_buf and installs a global SIGBUS signal handler. If multiple threads
execute the macro concurrently, they will race on installing the signal
handler and stomp on other threads' jump buffers, leading to incorrect test
behavior.

Make TEST_EXPECT_SIGBUS thread-safe with the following changes:

Share the KVM tests' global signal handler. sigaction() applies to all
threads; without sharing a global signal handler, one thread may have
removed the signal handler that another thread added, hence leading to
unexpected signals.

The alternative of layering signal handlers was considered, but calling
sigaction() within TEST_EXPECT_SIGBUS() necessarily creates a race. To
avoid adding new setup and teardown routines to do sigaction() and keep
usage of TEST_EXPECT_SIGBUS() simple, share the KVM tests' global signal
handler.

Opportunistically rename report_unexpected_signal to
catchall_signal_handler.

To continue to only expect SIGBUS within specific regions of code, use a
thread-specific variable, expecting_sigbus, to replace installing and
removing signal handlers.

Make the execution environment for the thread, sigjmp_buf, a
thread-specific variable.

As part of TEST_EXPECT_SIGBUS(), assert the prerequisite for this setup,
that the current signal handler is the catchall_signal_handler.

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/include/test_util.h | 32 +++++++++++++------------
 tools/testing/selftests/kvm/lib/kvm_util.c      | 18 ++++++++++----
 tools/testing/selftests/kvm/lib/test_util.c     |  7 ------
 3 files changed, 30 insertions(+), 27 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index d5825211f2727..75e98ec14107f 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -83,21 +83,23 @@ do {									\
 	__builtin_unreachable(); \
 } while (0)
 
-extern sigjmp_buf expect_sigbus_jmpbuf;
-void expect_sigbus_handler(int signum);
-
-#define TEST_EXPECT_SIGBUS(action)						\
-do {										\
-	struct sigaction sa_old, sa_new = {					\
-		.sa_handler = expect_sigbus_handler,				\
-	};									\
-										\
-	sigaction(SIGBUS, &sa_new, &sa_old);					\
-	if (sigsetjmp(expect_sigbus_jmpbuf, 1) == 0) {				\
-		action;								\
-		TEST_FAIL("'%s' should have triggered SIGBUS", #action);	\
-	}									\
-	sigaction(SIGBUS, &sa_old, NULL);					\
+extern __thread sigjmp_buf expect_sigbus_jmpbuf;
+extern __thread volatile sig_atomic_t expecting_sigbus;
+void catchall_signal_handler(int signum);
+
+#define TEST_EXPECT_SIGBUS(action)					\
+do {									\
+	struct sigaction __sa = {};					\
+									\
+	TEST_ASSERT_EQ(sigaction(SIGBUS, NULL, &__sa), 0);		\
+	TEST_ASSERT_EQ(__sa.sa_handler, &catchall_signal_handler);	\
+									\
+	expecting_sigbus = true;					\
+	if (sigsetjmp(expect_sigbus_jmpbuf, 1) == 0) {			\
+		action;							\
+		TEST_FAIL("'%s' should have triggered SIGBUS", #action);\
+	}								\
+	expecting_sigbus = false;					\
 } while (0)
 
 size_t parse_size(const char *size);
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 1188d0a6c0a5f..cac5624e99774 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -2316,13 +2316,20 @@ __weak void kvm_selftest_arch_init(void)
 {
 }
 
-static void report_unexpected_signal(int signum)
+__thread sigjmp_buf expect_sigbus_jmpbuf;
+__thread volatile sig_atomic_t expecting_sigbus;
+
+void catchall_signal_handler(int signum)
 {
+	switch (signum) {
+	case SIGBUS: {
+		if (expecting_sigbus)
+			siglongjmp(expect_sigbus_jmpbuf, 1);
+
+		TEST_FAIL("Unexpected SIGBUS (%d)\n", signum);
+	}
 #define KVM_CASE_SIGNUM(sig)					\
 	case sig: TEST_FAIL("Unexpected " #sig " (%d)\n", signum)
-
-	switch (signum) {
-	KVM_CASE_SIGNUM(SIGBUS);
 	KVM_CASE_SIGNUM(SIGSEGV);
 	KVM_CASE_SIGNUM(SIGILL);
 	KVM_CASE_SIGNUM(SIGFPE);
@@ -2334,12 +2341,13 @@ static void report_unexpected_signal(int signum)
 void __attribute((constructor)) kvm_selftest_init(void)
 {
 	struct sigaction sig_sa = {
-		.sa_handler = report_unexpected_signal,
+		.sa_handler = catchall_signal_handler,
 	};
 
 	/* Tell stdout not to buffer its content. */
 	setbuf(stdout, NULL);
 
+	expecting_sigbus = false;
 	sigaction(SIGBUS, &sig_sa, NULL);
 	sigaction(SIGSEGV, &sig_sa, NULL);
 	sigaction(SIGILL, &sig_sa, NULL);
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 4dff72f6bd346..89d6d1b572959 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -19,13 +19,6 @@
 #include "test_util.h"
 #include "kvm_syscalls.h"
 
-sigjmp_buf expect_sigbus_jmpbuf;
-
-void __attribute__((used)) expect_sigbus_handler(int signum)
-{
-	siglongjmp(expect_sigbus_jmpbuf, 1);
-}
-
 /*
  * Random number generator that is usable from guest code. This is the
  * Park-Miller LCG using standard constants.

-- 
2.55.0.897.gb25b4bd76c-goog

[PATCH v12 43/45] KVM: selftests: Set up page size and alignment independently for guest_memfd

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Currently, vm_mem_add derives the backing source page size, alignment
padding, and mmap size from the backing source type upfront before checking
if guest_memfd is being mmapped.

With shared memory also mmap()-ed from guest_memfd, the alignment of the
mmap-ed address needs to respect guest_memfd's backing page size.

Refactor the backing store setup to configure the backing source page
size, alignment, mmap flags, and mmap offset directly for guest_memfd
when it is mmapped, ignoring the backing source type.

Skip hugepage validation and anonymous memory madvise calls when mmapping
from guest_memfd, since those are not applicable when mmapping guest_memfd.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 74 ++++++++++++++++++------------
 1 file changed, 45 insertions(+), 29 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index cac5624e99774..3f559f207408f 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1034,11 +1034,12 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 {
 	int ret;
 	struct userspace_mem_region *region;
-	size_t backing_src_pagesz = get_backing_src_pagesz(src_type);
-	int mmap_flags = vm_mem_backing_src_alias(src_type)->flag;
 	size_t mem_size = npages * vm->page_size;
-	off_t mmap_offset = 0;
-	size_t alignment = 1;
+	size_t backing_src_pagesz;
+	off_t mmap_offset;
+	bool is_gmem_mmap;
+	size_t alignment;
+	int mmap_flags;
 
 	TEST_REQUIRE_SET_USER_MEMORY_REGION2();
 
@@ -1090,19 +1091,31 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 	/* Allocate and initialize new mem region structure. */
 	region = calloc(1, sizeof(*region));
 	TEST_ASSERT(region != NULL, "Insufficient Memory");
-	region->mmap_size = mem_size;
 
-	/*
-	 * When using THP mmap is not guaranteed to returned a hugepage aligned
-	 * address so we have to pad the mmap. Padding is not needed for HugeTLB
-	 * because mmap will always return an address aligned to the HugeTLB
-	 * page size.
-	 */
-	if (src_type == VM_MEM_SRC_ANONYMOUS_THP)
-		alignment = max(backing_src_pagesz, alignment);
+	is_gmem_mmap = (flags & KVM_MEM_GUEST_MEMFD) &&
+		       (gmem_flags & GUEST_MEMFD_FLAG_MMAP);
+
+	if (is_gmem_mmap) {
+		backing_src_pagesz = getpagesize();
+		alignment = 1;
+		mmap_flags = MAP_SHARED;
+		mmap_offset = gmem_offset;
+	} else {
+		backing_src_pagesz = get_backing_src_pagesz(src_type);
+		/*
+		 * When using THP mmap is not guaranteed to returned a hugepage aligned
+		 * address so we have to pad the mmap. Padding is not needed for HugeTLB
+		 * because mmap will always return an address aligned to the HugeTLB
+		 * page size.
+		 */
+		alignment = src_type == VM_MEM_SRC_ANONYMOUS_THP ? backing_src_pagesz : 1;
+		mmap_flags = vm_mem_backing_src_alias(src_type)->flag;
+		mmap_offset = 0;
+	}
 
 	TEST_ASSERT_EQ(gpa, align_up(gpa, backing_src_pagesz));
 
+	region->mmap_size = mem_size;
 	/* Add enough memory to align up if necessary */
 	if (alignment > 1)
 		region->mmap_size += alignment;
@@ -1129,10 +1142,8 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 	}
 
 	region->fd = -1;
-	if (flags & KVM_MEM_GUEST_MEMFD && gmem_flags & GUEST_MEMFD_FLAG_MMAP) {
+	if (is_gmem_mmap) {
 		region->fd = kvm_dup(gmem_fd);
-		mmap_flags = MAP_SHARED;
-		mmap_offset = gmem_offset;
 	} else if (backing_src_is_shared(src_type)) {
 		region->fd = kvm_memfd_alloc(region->mmap_size,
 					     src_type == VM_MEM_SRC_SHARED_HUGETLB);
@@ -1141,22 +1152,27 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
 	region->mmap_start = __kvm_mmap(region->mmap_size, PROT_READ | PROT_WRITE,
 					mmap_flags, region->fd, mmap_offset);
 
-	TEST_ASSERT(!is_backing_src_hugetlb(src_type) ||
-		    region->mmap_start == align_ptr_up(region->mmap_start, backing_src_pagesz),
-		    "mmap_start %p is not aligned to HugeTLB page size 0x%lx",
-		    region->mmap_start, backing_src_pagesz);
-
 	/* Align host address */
 	region->host_mem = align_ptr_up(region->mmap_start, alignment);
 
-	/* As needed perform madvise */
-	if ((src_type == VM_MEM_SRC_ANONYMOUS ||
-	     src_type == VM_MEM_SRC_ANONYMOUS_THP) && thp_configured()) {
-		ret = madvise(region->host_mem, mem_size,
-			      src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
-		TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %s",
-			    region->host_mem, mem_size,
-			    vm_mem_backing_src_alias(src_type)->name);
+	if (!is_gmem_mmap) {
+		TEST_ASSERT(!is_backing_src_hugetlb(src_type) ||
+			    region->mmap_start ==
+			    align_ptr_up(region->mmap_start, backing_src_pagesz),
+			    "mmap_start %p is not aligned to HugeTLB page size 0x%lx",
+			    region->mmap_start, backing_src_pagesz);
+
+		/* As needed perform madvise */
+		if ((src_type == VM_MEM_SRC_ANONYMOUS ||
+		     src_type == VM_MEM_SRC_ANONYMOUS_THP) && thp_configured()) {
+			int advice = src_type == VM_MEM_SRC_ANONYMOUS ?
+				     MADV_NOHUGEPAGE : MADV_HUGEPAGE;
+
+			ret = madvise(region->host_mem, mem_size, advice);
+			TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %s",
+				    region->host_mem, mem_size,
+				    vm_mem_backing_src_alias(src_type)->name);
+		}
 	}
 
 	region->backing_src_type = src_type;

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 43/45] KVM: selftests: Set up page size and alignment independently for guest_memfd

[Fuad Tabba]

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Ackerley Tng <ackerleytng@google.com>
>
> Currently, vm_mem_add derives the backing source page size, alignment
> padding, and mmap size from the backing source type upfront before checking
> if guest_memfd is being mmapped.
>
> With shared memory also mmap()-ed from guest_memfd, the alignment of the
> mmap-ed address needs to respect guest_memfd's backing page size.
>
> Refactor the backing store setup to configure the backing source page
> size, alignment, mmap flags, and mmap offset directly for guest_memfd
> when it is mmapped, ignoring the backing source type.
>
> Skip hugepage validation and anonymous memory madvise calls when mmapping
> from guest_memfd, since those are not applicable when mmapping guest_memfd.
>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

Cheers,
/fuad


> ---
>  tools/testing/selftests/kvm/lib/kvm_util.c | 74 ++++++++++++++++++------------
>  1 file changed, 45 insertions(+), 29 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index cac5624e99774..3f559f207408f 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -1034,11 +1034,12 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
>  {
>         int ret;
>         struct userspace_mem_region *region;
> -       size_t backing_src_pagesz = get_backing_src_pagesz(src_type);
> -       int mmap_flags = vm_mem_backing_src_alias(src_type)->flag;
>         size_t mem_size = npages * vm->page_size;
> -       off_t mmap_offset = 0;
> -       size_t alignment = 1;
> +       size_t backing_src_pagesz;
> +       off_t mmap_offset;
> +       bool is_gmem_mmap;
> +       size_t alignment;
> +       int mmap_flags;
>
>         TEST_REQUIRE_SET_USER_MEMORY_REGION2();
>
> @@ -1090,19 +1091,31 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
>         /* Allocate and initialize new mem region structure. */
>         region = calloc(1, sizeof(*region));
>         TEST_ASSERT(region != NULL, "Insufficient Memory");
> -       region->mmap_size = mem_size;
>
> -       /*
> -        * When using THP mmap is not guaranteed to returned a hugepage aligned
> -        * address so we have to pad the mmap. Padding is not needed for HugeTLB
> -        * because mmap will always return an address aligned to the HugeTLB
> -        * page size.
> -        */
> -       if (src_type == VM_MEM_SRC_ANONYMOUS_THP)
> -               alignment = max(backing_src_pagesz, alignment);
> +       is_gmem_mmap = (flags & KVM_MEM_GUEST_MEMFD) &&
> +                      (gmem_flags & GUEST_MEMFD_FLAG_MMAP);
> +
> +       if (is_gmem_mmap) {
> +               backing_src_pagesz = getpagesize();
> +               alignment = 1;
> +               mmap_flags = MAP_SHARED;
> +               mmap_offset = gmem_offset;
> +       } else {
> +               backing_src_pagesz = get_backing_src_pagesz(src_type);
> +               /*
> +                * When using THP mmap is not guaranteed to returned a hugepage aligned
> +                * address so we have to pad the mmap. Padding is not needed for HugeTLB
> +                * because mmap will always return an address aligned to the HugeTLB
> +                * page size.
> +                */
> +               alignment = src_type == VM_MEM_SRC_ANONYMOUS_THP ? backing_src_pagesz : 1;
> +               mmap_flags = vm_mem_backing_src_alias(src_type)->flag;
> +               mmap_offset = 0;
> +       }
>
>         TEST_ASSERT_EQ(gpa, align_up(gpa, backing_src_pagesz));
>
> +       region->mmap_size = mem_size;
>         /* Add enough memory to align up if necessary */
>         if (alignment > 1)
>                 region->mmap_size += alignment;
> @@ -1129,10 +1142,8 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
>         }
>
>         region->fd = -1;
> -       if (flags & KVM_MEM_GUEST_MEMFD && gmem_flags & GUEST_MEMFD_FLAG_MMAP) {
> +       if (is_gmem_mmap) {
>                 region->fd = kvm_dup(gmem_fd);
> -               mmap_flags = MAP_SHARED;
> -               mmap_offset = gmem_offset;
>         } else if (backing_src_is_shared(src_type)) {
>                 region->fd = kvm_memfd_alloc(region->mmap_size,
>                                              src_type == VM_MEM_SRC_SHARED_HUGETLB);
> @@ -1141,22 +1152,27 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
>         region->mmap_start = __kvm_mmap(region->mmap_size, PROT_READ | PROT_WRITE,
>                                         mmap_flags, region->fd, mmap_offset);
>
> -       TEST_ASSERT(!is_backing_src_hugetlb(src_type) ||
> -                   region->mmap_start == align_ptr_up(region->mmap_start, backing_src_pagesz),
> -                   "mmap_start %p is not aligned to HugeTLB page size 0x%lx",
> -                   region->mmap_start, backing_src_pagesz);
> -
>         /* Align host address */
>         region->host_mem = align_ptr_up(region->mmap_start, alignment);
>
> -       /* As needed perform madvise */
> -       if ((src_type == VM_MEM_SRC_ANONYMOUS ||
> -            src_type == VM_MEM_SRC_ANONYMOUS_THP) && thp_configured()) {
> -               ret = madvise(region->host_mem, mem_size,
> -                             src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
> -               TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %s",
> -                           region->host_mem, mem_size,
> -                           vm_mem_backing_src_alias(src_type)->name);
> +       if (!is_gmem_mmap) {
> +               TEST_ASSERT(!is_backing_src_hugetlb(src_type) ||
> +                           region->mmap_start ==
> +                           align_ptr_up(region->mmap_start, backing_src_pagesz),
> +                           "mmap_start %p is not aligned to HugeTLB page size 0x%lx",
> +                           region->mmap_start, backing_src_pagesz);
> +
> +               /* As needed perform madvise */
> +               if ((src_type == VM_MEM_SRC_ANONYMOUS ||
> +                    src_type == VM_MEM_SRC_ANONYMOUS_THP) && thp_configured()) {
> +                       int advice = src_type == VM_MEM_SRC_ANONYMOUS ?
> +                                    MADV_NOHUGEPAGE : MADV_HUGEPAGE;
> +
> +                       ret = madvise(region->host_mem, mem_size, advice);
> +                       TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %s",
> +                                   region->host_mem, mem_size,
> +                                   vm_mem_backing_src_alias(src_type)->name);
> +               }
>         }
>
>         region->backing_src_type = src_type;
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

[PATCH v12 44/45] KVM: selftests: Update private_mem_conversions_test for in-place conversions

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@google.com>

Update private_mem_conversions_test for in-place conversions. In-place
conversions support is detected in selftests with kvm_has_gmem_attributes.

With in-place conversions, specifying userspace_addr from some other memory
provider that is not the guest_memfd associated with the memslot is a user
error, since KVM will only use both shared and private memory from the
guest_memfd.

Hence, when kvm_has_gmem_attributes, only test in-place conversions with
single backing, where guest_memfd provides both shared and private memory.

For single backing, guest_memfd must be created with
GUEST_MEMFD_FLAG_MMAP. Initialize the guest_memfd as shared to align with
how memory would default to shared when shared/private state was tracked at
the VM level (the test expects this, it was written for
non-in-place-conversions).

When handling a hypercall to set attributes, use
vm_mem_set_memory_attributes() to send the ioctl to the guest_memfd instead
of the VM.

When testing in-place conversions (single-backing), don't allow the user to
configure src_type, since src_type will be ignored. Don't use src_type to
determine alignment for rounding up per-cpu test memory size, since
guest_memfd's backing page size is always the system PAGE_SIZE.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../kvm/x86/private_mem_conversions_test.c         | 57 +++++++++++++++++-----
 1 file changed, 44 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
index cf50e9a332c5b..33b610383693b 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -306,9 +306,12 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
 	if (do_fallocate)
 		vm_guest_mem_fallocate(vm, gpa, size, map_shared);
 
-	if (set_attributes)
-		vm_set_memory_attributes(vm, gpa, size,
-					 map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE);
+	if (set_attributes) {
+		u64 attrs = map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
+
+		vm_mem_set_memory_attributes(vm, gpa, size, attrs);
+	}
+
 	run->hypercall.ret = 0;
 }
 
@@ -352,8 +355,21 @@ static void *__test_mem_conversions(void *__vcpu)
 				size_t nr_bytes = min_t(size_t, vm->page_size, size - i);
 				u8 *hva = addr_gpa2hva(vm, gpa + i);
 
-				/* In all cases, the host should observe the shared data. */
-				memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
+				if (kvm_has_gmem_attributes &&
+				    uc.args[0] == SYNC_PRIVATE) {
+					TEST_EXPECT_SIGBUS(READ_ONCE(*hva));
+				} else {
+					/*
+					 * If not testing in-place conversion
+					 * (dual backing), the host should
+					 * always observe shared data, since the
+					 * shared memory is a separate page.
+					 *
+					 * For SYNC_SHARED, test that the host
+					 * can see shared memory.
+					 */
+					memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
+				}
 
 				/* For shared, write the new pattern to guest memory. */
 				if (uc.args[0] == SYNC_SHARED)
@@ -369,20 +385,29 @@ static void *__test_mem_conversions(void *__vcpu)
 	}
 }
 
+/* Align each vCPU's chunk of memory naturally to the size of the backing store. */
+static size_t compute_per_cpu_size(enum vm_mem_backing_src_type src_type)
+{
+	size_t alignment;
+
+	if (kvm_has_gmem_attributes)
+		alignment = getpagesize();
+	else
+		alignment = get_backing_src_pagesz(src_type);
+
+	return align_up(PER_CPU_DATA_SIZE, max_t(size_t, SZ_2M, alignment));
+}
+
 static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_vcpus,
 				 u32 nr_memslots)
 {
-	/*
-	 * Allocate enough memory so that each vCPU's chunk of memory can be
-	 * naturally aligned with respect to the size of the backing store.
-	 */
-	const size_t alignment = max_t(size_t, SZ_2M, get_backing_src_pagesz(src_type));
-	const size_t per_cpu_size = align_up(PER_CPU_DATA_SIZE, alignment);
+	const size_t per_cpu_size = compute_per_cpu_size(src_type);
 	const size_t memfd_size = per_cpu_size * nr_vcpus;
 	const size_t slot_size = memfd_size / nr_memslots;
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
 	pthread_t threads[KVM_MAX_VCPUS];
 	struct kvm_vm *vm;
+	u64 gmem_flags;
 	int memfd, i;
 
 	const struct vm_shape shape = {
@@ -397,12 +422,16 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_v
 
 	vm_enable_cap(vm, KVM_CAP_EXIT_HYPERCALL, (1 << KVM_HC_MAP_GPA_RANGE));
 
-	memfd = vm_create_guest_memfd(vm, memfd_size, 0);
+	gmem_flags = 0;
+	if (kvm_has_gmem_attributes)
+		gmem_flags = GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_INIT_SHARED;
+
+	memfd = vm_create_guest_memfd(vm, memfd_size, gmem_flags);
 
 	for (i = 0; i < nr_memslots; i++)
 		vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i,
 			   BASE_DATA_SLOT + i, slot_size / vm->page_size,
-			   KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, 0);
+			   KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, gmem_flags);
 
 	for (i = 0; i < nr_vcpus; i++) {
 		gpa_t gpa =  BASE_DATA_GPA + i * per_cpu_size;
@@ -462,6 +491,8 @@ int main(int argc, char *argv[])
 	while ((opt = getopt(argc, argv, "hm:s:n:")) != -1) {
 		switch (opt) {
 		case 's':
+			TEST_ASSERT(!kvm_has_gmem_attributes,
+				    "src_type is only configurable when testing without in-place conversion");
 			src_type = parse_backing_src_type(optarg);
 			break;
 		case 'n':

-- 
2.55.0.897.gb25b4bd76c-goog

Re: [PATCH v12 44/45] KVM: selftests: Update private_mem_conversions_test for in-place conversions

[Fuad Tabba]

On Mon, 31 Aug 2026 at 01:25, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@kernel.org> wrote:
>
> From: Ackerley Tng <ackerleytng@google.com>
>
> Update private_mem_conversions_test for in-place conversions. In-place
> conversions support is detected in selftests with kvm_has_gmem_attributes.
>
> With in-place conversions, specifying userspace_addr from some other memory
> provider that is not the guest_memfd associated with the memslot is a user
> error, since KVM will only use both shared and private memory from the
> guest_memfd.
>
> Hence, when kvm_has_gmem_attributes, only test in-place conversions with
> single backing, where guest_memfd provides both shared and private memory.
>
> For single backing, guest_memfd must be created with
> GUEST_MEMFD_FLAG_MMAP. Initialize the guest_memfd as shared to align with
> how memory would default to shared when shared/private state was tracked at
> the VM level (the test expects this, it was written for
> non-in-place-conversions).
>
> When handling a hypercall to set attributes, use
> vm_mem_set_memory_attributes() to send the ioctl to the guest_memfd instead
> of the VM.
>
> When testing in-place conversions (single-backing), don't allow the user to
> configure src_type, since src_type will be ignored. Don't use src_type to
> determine alignment for rounding up per-cpu test memory size, since
> guest_memfd's backing page size is always the system PAGE_SIZE.
>
> Co-developed-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

Cheers,
/fuad


> ---
>  .../kvm/x86/private_mem_conversions_test.c         | 57 +++++++++++++++++-----
>  1 file changed, 44 insertions(+), 13 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
> index cf50e9a332c5b..33b610383693b 100644
> --- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
> +++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
> @@ -306,9 +306,12 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
>         if (do_fallocate)
>                 vm_guest_mem_fallocate(vm, gpa, size, map_shared);
>
> -       if (set_attributes)
> -               vm_set_memory_attributes(vm, gpa, size,
> -                                        map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE);
> +       if (set_attributes) {
> +               u64 attrs = map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
> +
> +               vm_mem_set_memory_attributes(vm, gpa, size, attrs);
> +       }
> +
>         run->hypercall.ret = 0;
>  }
>
> @@ -352,8 +355,21 @@ static void *__test_mem_conversions(void *__vcpu)
>                                 size_t nr_bytes = min_t(size_t, vm->page_size, size - i);
>                                 u8 *hva = addr_gpa2hva(vm, gpa + i);
>
> -                               /* In all cases, the host should observe the shared data. */
> -                               memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
> +                               if (kvm_has_gmem_attributes &&
> +                                   uc.args[0] == SYNC_PRIVATE) {
> +                                       TEST_EXPECT_SIGBUS(READ_ONCE(*hva));
> +                               } else {
> +                                       /*
> +                                        * If not testing in-place conversion
> +                                        * (dual backing), the host should
> +                                        * always observe shared data, since the
> +                                        * shared memory is a separate page.
> +                                        *
> +                                        * For SYNC_SHARED, test that the host
> +                                        * can see shared memory.
> +                                        */
> +                                       memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
> +                               }
>
>                                 /* For shared, write the new pattern to guest memory. */
>                                 if (uc.args[0] == SYNC_SHARED)
> @@ -369,20 +385,29 @@ static void *__test_mem_conversions(void *__vcpu)
>         }
>  }
>
> +/* Align each vCPU's chunk of memory naturally to the size of the backing store. */
> +static size_t compute_per_cpu_size(enum vm_mem_backing_src_type src_type)
> +{
> +       size_t alignment;
> +
> +       if (kvm_has_gmem_attributes)
> +               alignment = getpagesize();
> +       else
> +               alignment = get_backing_src_pagesz(src_type);
> +
> +       return align_up(PER_CPU_DATA_SIZE, max_t(size_t, SZ_2M, alignment));
> +}
> +
>  static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_vcpus,
>                                  u32 nr_memslots)
>  {
> -       /*
> -        * Allocate enough memory so that each vCPU's chunk of memory can be
> -        * naturally aligned with respect to the size of the backing store.
> -        */
> -       const size_t alignment = max_t(size_t, SZ_2M, get_backing_src_pagesz(src_type));
> -       const size_t per_cpu_size = align_up(PER_CPU_DATA_SIZE, alignment);
> +       const size_t per_cpu_size = compute_per_cpu_size(src_type);
>         const size_t memfd_size = per_cpu_size * nr_vcpus;
>         const size_t slot_size = memfd_size / nr_memslots;
>         struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
>         pthread_t threads[KVM_MAX_VCPUS];
>         struct kvm_vm *vm;
> +       u64 gmem_flags;
>         int memfd, i;
>
>         const struct vm_shape shape = {
> @@ -397,12 +422,16 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_v
>
>         vm_enable_cap(vm, KVM_CAP_EXIT_HYPERCALL, (1 << KVM_HC_MAP_GPA_RANGE));
>
> -       memfd = vm_create_guest_memfd(vm, memfd_size, 0);
> +       gmem_flags = 0;
> +       if (kvm_has_gmem_attributes)
> +               gmem_flags = GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_INIT_SHARED;
> +
> +       memfd = vm_create_guest_memfd(vm, memfd_size, gmem_flags);
>
>         for (i = 0; i < nr_memslots; i++)
>                 vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i,
>                            BASE_DATA_SLOT + i, slot_size / vm->page_size,
> -                          KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, 0);
> +                          KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, gmem_flags);
>
>         for (i = 0; i < nr_vcpus; i++) {
>                 gpa_t gpa =  BASE_DATA_GPA + i * per_cpu_size;
> @@ -462,6 +491,8 @@ int main(int argc, char *argv[])
>         while ((opt = getopt(argc, argv, "hm:s:n:")) != -1) {
>                 switch (opt) {
>                 case 's':
> +                       TEST_ASSERT(!kvm_has_gmem_attributes,
> +                                   "src_type is only configurable when testing without in-place conversion");
>                         src_type = parse_backing_src_type(optarg);
>                         break;
>                 case 'n':
>
> --
> 2.55.0.897.gb25b4bd76c-goog
>
>

[PATCH v12 45/45] KVM: selftests: Update private memory exits test to work with per-gmem attributes

[Ackerley Tng via B4 Relay]

From: Sean Christopherson <seanjc@google.com>

Skip setting memory to private in the private memory exits test when using
per-gmem memory attributes, as memory is initialized to private by default
for guest_memfd, and using vm_mem_set_private() on a guest_memfd instance
requires creating guest_memfd with GUEST_MEMFD_FLAG_MMAP (which is totally
doable, but would need to be conditional and is ultimately unnecessary).

Expect an emulated MMIO instead of a memory fault exit when attributes are
per-gmem, as deleting the memslot effectively drops the private status,
i.e. the GPA becomes shared and thus supports emulated MMIO.

Skip the "memslot not private" test entirely, as private vs. shared state
for x86 software-protected VMs comes from the memory attributes themselves,
and so when doing in-place conversions there can never be a disconnect
between the expected and actual states.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../selftests/kvm/x86/private_mem_kvm_exits_test.c | 36 ++++++++++++++++++----
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86/private_mem_kvm_exits_test.c b/tools/testing/selftests/kvm/x86/private_mem_kvm_exits_test.c
index e6d16e9d61200..f7228e0f1ac61 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_kvm_exits_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_kvm_exits_test.c
@@ -62,8 +62,9 @@ static void test_private_access_memslot_deleted(void)
 
 	virt_map(vm, EXITS_TEST_GVA, EXITS_TEST_GPA, EXITS_TEST_NPAGES);
 
-	/* Request to access page privately */
-	vm_mem_set_private(vm, EXITS_TEST_GPA, EXITS_TEST_SIZE);
+	/* Request to access page privately. */
+	if (!kvm_has_gmem_attributes)
+		vm_mem_set_private(vm, EXITS_TEST_GPA, EXITS_TEST_SIZE);
 
 	kvm_pthread_create(&vm_thread, NULL,
 			   (pthread_fn_t)run_vcpu_get_exit_reason, (void *)vcpu);
@@ -73,10 +74,26 @@ static void test_private_access_memslot_deleted(void)
 	kvm_pthread_join(vm_thread, &thread_return);
 	exit_reason = (u32)(u64)thread_return;
 
-	TEST_ASSERT_EQ(exit_reason, KVM_EXIT_MEMORY_FAULT);
-	TEST_ASSERT_EQ(vcpu->run->memory_fault.flags, KVM_MEMORY_EXIT_FLAG_PRIVATE);
-	TEST_ASSERT_EQ(vcpu->run->memory_fault.gpa, EXITS_TEST_GPA);
-	TEST_ASSERT_EQ(vcpu->run->memory_fault.size, EXITS_TEST_SIZE);
+	/*
+	 * If attributes are tracked per-gmem, deleting the memslot that points
+	 * at the gmem instance effectively makes the memory shared, and so the
+	 * read should trigger emulated MMIO.
+	 *
+	 * If attributes are tracked per-VM, deleting the memslot shouldn't
+	 * affect the private attribute, and so KVM should generate a memory
+	 * fault exit (emulated MMIO on private GPAs is disallowed).
+	 */
+	if (kvm_has_gmem_attributes) {
+		TEST_ASSERT_EQ(exit_reason, KVM_EXIT_MMIO);
+		TEST_ASSERT_EQ(vcpu->run->mmio.phys_addr, EXITS_TEST_GPA);
+		TEST_ASSERT_EQ(vcpu->run->mmio.len, sizeof(u64));
+		TEST_ASSERT_EQ(vcpu->run->mmio.is_write, false);
+	} else {
+		TEST_ASSERT_EQ(exit_reason, KVM_EXIT_MEMORY_FAULT);
+		TEST_ASSERT_EQ(vcpu->run->memory_fault.flags, KVM_MEMORY_EXIT_FLAG_PRIVATE);
+		TEST_ASSERT_EQ(vcpu->run->memory_fault.gpa, EXITS_TEST_GPA);
+		TEST_ASSERT_EQ(vcpu->run->memory_fault.size, EXITS_TEST_SIZE);
+	}
 
 	kvm_vm_free(vm);
 }
@@ -87,6 +104,13 @@ static void test_private_access_memslot_not_private(void)
 	struct kvm_vcpu *vcpu;
 	u32 exit_reason;
 
+	/*
+	 * Accessing non-private memory as private with a software-protected VM
+	 * isn't possible when doing in-place conversions.
+	 */
+	if (kvm_has_gmem_attributes)
+		return;
+
 	vm = vm_create_shape_with_one_vcpu(protected_vm_shape, &vcpu,
 					   guest_repeatedly_read);
 

-- 
2.55.0.897.gb25b4bd76c-goog