[PATCH v11 00/46] guest_memfd: In-place conversion support

[PATCH v11 00/46] guest_memfd: In-place conversion support

[Ackerley Tng]

Here's v11, thanks everyone for the reviewing and testing!  We're at
~5 weeks to soft-close at 7.3-rc5 for the 7.4 merge.

v11 is based on kvm-x86/next, and a cherry-picked version of David's
refactoring patch [6], and is now dependent on another series [5],
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-v11

v11 changes:

+ Added this to "KVM: guest_memfd: Introduce per-gmem attributes, use
    to guard user mappings" as Yan requested 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().
+ Added patch "KVM: Rename kvm_mem_is_private() to
  kvm_is_private_gfn()"
    + I added it before "KVM: Provide generic interface for checking
      memory private/shared status", so that this second patch can
      clarify the VM version for kvm_is_private_gfn() to
      kvm_vm_is_private_gfn()
    + In summary, we have
        + kvm_is_private_gfn(kvm, gfn), kvm_vm_is_private_gfn(kvm,
          gfn), kvm_gmem_is_private_gfn(kvm, gfn)
		+ kvm_gmem_is_private_mem(inode, index): called by
          kvm_gmem_is_private_gfn(kvm, gfn)
+ Added documentation for module parameter
  kvm.gmem_in_place_conversion in "KVM: Let userspace disable per-VM
  mem attributes, enable per-gmem attributes" as discussed by Yan and
  Sean in [1]. I was reminded after more discussions on v10 [2][3].
+ Added Sean's patch "KVM: guest_memfd: Invalidate both SHARED and
  PRIVATE mappings", then a no-functional-change patch to allow filter
  to be passed to kvm_gmem_invalidate_start(), then the actual patch
  that introduces conversions.
+ Split out a patch that just updates private_mem_conversions_test to
  support gmem_in_place_conversion, as Xiaoyao suggested
+ I realized that in the v10 patch "Update
  private_mem_conversions_test to mmap() guest_memfd", the requirement
  to have src_type be VM_MEM_SRC_SHMEM is an artificial
  requirement. If private_mem_conversions_test and vm_mem_add()
  figured out alignment correctly for guest_memfd in-place conversion,
  that requirement could be removed. Added a new patch "KVM:
  selftests: Set up page size and alignment independently for
  guest_memfd".
+ Renamed v10 patch "Update private_mem_conversions_test to mmap()
  guest_memfd" to "KVM: selftests: Test in-place conversions in
  private_mem_conversions_test" to better reflect what changed.
+ Regarding conversions of the VMSA page, Sashiko pointed out
  something in the prereq patch series "Stop returning struct page
  from guest_memfd PFN lookup". That turned out to already be handled.
  :) kvm_gmem_invalidate_start eventually calls
  sev_gmem_invalidate_range(), which ensures that if a VMSA page is
  being converted, the vCPU associated with the VMSA page will not be
  allowed to enter the guest until kvm_gmem_invalidate_end(). This
  allows kvm_gmem_make_shared() and eventually rmp_make_shared() to
  never fail due to a VMSA page being in-use (since the vCPU using the
  VMSA page was prevented from running). Conversions fit right into
  the invalidate_start and invalidate_end model :).

Here's v11 with extra tests:

https://github.com/googleprodkernel/linux-cc/commits/guest_memfd-inplace-conversion-coco-selftests-v11

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

Also tested ./gmem_convert_fault_race (this test is not for merging)

This test reproduces the race that Yan brought up in v10 of this
series (without TDX), where a vCPU faulting in a page using
kvm_gmem_get_pfn() would cause conversion failures.

The test has 4 vCPUs continuously try to fault in the pages while
conversion to private is attempted. Each attempt is a shared to
private conversion. In between attempts, the entire range is converted
back to shared in preparation for the next attempt.

Without patch series "Stop returning struct page from guest_memfd PFN
lookup", the race causes conversions to fail with -EAGAIN quite
quickly:

Random seed: 0x704e99ea
Reproduced -EAGAIN on attempt 1374 at error_offset 0x30000

Random seed: 0x3123e3de
Reproduced -EAGAIN on attempt 983 at error_offset 0x137000

Random seed: 0x2900e25d
Reproduced -EAGAIN on attempt 870 at error_offset 0x1e1000

Random seed: 0x721a2540
Reproduced -EAGAIN on attempt 1571 at error_offset 0x1ce000

Random seed: 0x46db97b4
Reproduced -EAGAIN on attempt 6601 at error_offset 0x1af000

Random seed: 0x7eca9fbd
Reproduced -EAGAIN on attempt 5894 at error_offset 0x19c000

Random seed: 0x41355a8a
Reproduced -EAGAIN on attempt 369 at error_offset 0x15a000

With patch series, within 10000 iterations there's no -EAGAIN:

Random seed: 0x51fb3075
__vm_create: mode='PA-bits:ANY, VA-bits:48 or 57, 4K pages' type='1', pages='674'
Guest physical address width detected: 46
Guest virtual address width detected: 48
==== Test Assertion Failure ====
  gmem_convert_fault_race.c:170: iter < iterations
  pid=243 tid=243 errno=0 - Success
     1  0x0000000000243215: test_gmem_convert_fault_race at gmem_convert_fault_race.c:168
     2   (inlined by) main at gmem_convert_fault_race.c:198
     3  0x0000000000267022: __libc_start_call_main at dsa.c:?
     4  0x000000000026919c: __libc_start_main at dsa.c:?
     5  0x0000000000242ba0: _start at ??:?
  Failed to reproduce -EAGAIN within 10000 attempts

[1] https://lore.kernel.org/all/aj7NwCRwWEfLK-gQ@google.com/
[2] https://lore.kernel.org/all/ed483d25-d908-4248-b8c7-862dd35dc6d4@kernel.org/
[3] https://lore.kernel.org/all/a410cca6-0776-44af-8353-9b7375e2fd4e@intel.com/
[4] https://lore.kernel.org/all/CAEvNRgH5ZQPGYzg+YdtEktZ72DgK9PBbzcmC_QFN6M0_6wuo1w@mail.gmail.com/
[5] https://lore.kernel.org/all/20260820-gmem-no-return-page-v3-0-3bf8f80a7b4d@google.com/
[6] https://lore.kernel.org/all/20260825015337.B58AD1F000E9@smtp.kernel.org/

Older series:

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: 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: Support guest_memfd attributes in private_mem_conversions_test
      KVM: selftests: Set up page size and alignment independently for guest_memfd
      KVM: selftests: Test in-place conversions in private_mem_conversions_test

David Hildenbrand (Arm) (1):
      mm/gup: factor out LRU cache draining for folio into lru_cache_drain_for_folio()

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                     |  85 +++-
 .../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/linux/swap.h                               |  11 +-
 include/trace/events/kvm.h                         |   6 +-
 include/uapi/linux/kvm.h                           |  16 +
 mm/gup.c                                           |  20 +-
 mm/swap.c                                          |  48 ++
 tools/testing/selftests/kvm/Makefile.kvm           |   1 +
 tools/testing/selftests/kvm/include/kvm_util.h     | 139 +++++-
 tools/testing/selftests/kvm/include/test_util.h    |  32 +-
 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         |  82 +++-
 .../selftests/kvm/x86/private_mem_kvm_exits_test.c |  36 +-
 virt/kvm/Kconfig                                   |   3 -
 virt/kvm/guest_memfd.c                             | 467 +++++++++++++++++--
 virt/kvm/kvm_main.c                                |  92 ++--
 28 files changed, 1701 insertions(+), 299 deletions(-)
---
base-commit: 5619ae2be01e78f6a479706b659fae07823467c1
change-id: 20260225-gmem-inplace-conversion-bd0dbd39753a

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

[PATCH v11 01/46] KVM: guest_memfd: Optimize away conversion overheads via dead-code elimination

[Ackerley Tng]

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 589762140c3ef..8f8e5b6b70134 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);

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 02/46] KVM: guest_memfd: Use kvm_mem_is_private() when populating guest_memfd memory

[Ackerley Tng]

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 8f8e5b6b70134..2c5857a73ec94 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;
 	}

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 03/46] KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings

[Ackerley Tng]

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 2c5857a73ec94..154fc9622640d 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)

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 04/46] KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES

[Ackerley Tng]

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 4b3681796c752..29e41d334cedf 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;
 

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 05/46] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined

[Ackerley Tng]

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;
 }

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 06/46] KVM: Rename memory attribute APIs to prepare for in-place gmem conversion

[Ackerley Tng]

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:

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 07/46] KVM: Rename kvm_mem_is_private() to kvm_is_private_gfn()

[Ackerley Tng]

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 154fc9622640d..b9fee68c90311 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;
 	}

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 08/46] KVM: Provide generic interface for checking memory private/shared status

[Ackerley Tng]

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();

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 09/46] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion

[Ackerley Tng]

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>
---
 include/linux/kvm_host.h |  6 ++++++
 virt/kvm/guest_memfd.c   | 26 ++++++++++++++++++++++++++
 virt/kvm/kvm_main.c      | 12 +++++++++++-
 3 files changed, 43 insertions(+), 1 deletion(-)

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 b9fee68c90311..5399ae4aae0e7 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

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 10/46] KVM: Consolidate private memory and guest_memfd ifdeffery in kvm_host.h

[Ackerley Tng]

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);

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 11/46] KVM: guest_memfd: Invalidate both SHARED and PRIVATE mappings for in-place conversions

[Ackerley Tng]

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).  And vice versa,
a PUNCH_HOLE on a SHARED gmem (if userspace is using an INIT_SHARED gmem
for the shared branch of a memslot) could invalidate the PRIVATE mappings
of a different gmem instance.  The latter case in particular would be a
functional bug, as spuriously zapping PRIVATE SPTEs is fatal to TDX, as
doing so destroys the contents of the memory.

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 5399ae4aae0e7..d4a9877b29ab0 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);

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 12/46] KVM: guest_memfd: Pass mapping type filter to invalidation helper

[Ackerley Tng]

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 d4a9877b29ab0..ab29e7f555787 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

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 13/46] KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2

[Ackerley Tng]

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 that 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 |  63 +++++++++++++++++++++-
 include/uapi/linux/kvm.h       |  15 ++++++
 virt/kvm/guest_memfd.c         | 119 +++++++++++++++++++++++++++++++++++++++++
 virt/kvm/kvm_main.c            |  23 +++++---
 4 files changed, 212 insertions(+), 8 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 4eb7e75a7473f..7aad097ffd392 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.
@@ -6393,6 +6393,8 @@ 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
 -------------------------------
 
@@ -6586,6 +6588,65 @@ 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``.
 
+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`.
+
 .. _kvm_run:
 
 5. The kvm_run structure
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 9fc8dfdfd65ff..ccbf7c475ec29 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -998,6 +998,7 @@ struct kvm_enable_cap {
 #define KVM_CAP_S390_VSIE_ESAMODE 248
 #define KVM_CAP_S390_HPAGE_2G 249
 #define KVM_CAP_ARM_PMU_V3_STRICT 250
+#define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 251
 
 struct kvm_irq_routing_irqchip {
 	__u32 irqchip;
@@ -1650,6 +1651,20 @@ 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 ab29e7f555787..2987611587b18 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;

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 14/46] KVM: guest_memfd: Ensure pages are not in use before conversion

[Ackerley Tng]

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 7aad097ffd392..f88d65b78c504 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6594,7 +6594,7 @@ 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:
@@ -6603,6 +6603,8 @@ 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
   ========== ===============================================================
 
@@ -6616,6 +6618,7 @@ Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
 ::
 
   struct kvm_memory_attributes2 {
+	/* in */
 	union {
 		__u64 address;
 		__u64 offset;
@@ -6623,7 +6626,9 @@ 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)
@@ -6645,6 +6650,16 @@ 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`.
 
 .. _kvm_run:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ccbf7c475ec29..0ac9e6a790111 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1662,7 +1662,8 @@ 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 2987611587b18..e4722eb6405b6 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,

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 15/46] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion

[Ackerley Tng]

When memory in guest_memfd is converted from private to shared, the
platform-specific state associated with the guest-private pages must be
invalidated or cleaned up.

Iterate over the folios in the affected range and call the
kvm_arch_gmem_make_shared() hook for each PFN range. This allows
architectures to update hardware metadata or encryption states to
transition pages to the shared state.

Invoke this helper after indicating to KVM's mmu code that an invalidation
is in progress to stop in-flight page faults from succeeding. Calling the
invalidation helper also calls the arch invalidate hook. For SNP, this
kicks any vCPU with a registered VMSA within the range being converted out
of the guest. This ensures that make_shared never fails due to the VMSA
page being in-use and is important because if make_shared fails, the RMP
table would track the page as private while guest_memfd is unaware and
tracks the page as shared.

Omit support for calling the arch hook to make private, since SNP, the only
implementer of the arch make-private hook today, would actually prefer
making private only just before faulting memory into the NPTs.

Calling the make-private arch hook would require iterating both bindings
and the filemap to find the intersection of bindings and allocated
folios. On top of that, SNP would need to figure out whether to actually
make private based on whether the memory is about to be faulted, or
whether it is a conversion.

Calling the make-shared arch hook and not the make-private arch hook does
leak SNP-specific details into guest_memfd (as in, why only make-shared
during conversions but not make-private?), but the additional complexity is
not worth taking on until guest_memfd has a user actually requiring an arch
make-private call.

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 29e41d334cedf..147b3e529cd26 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 e4722eb6405b6..d1134b23576e4 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);

-- 
2.55.0.887.g758fc8c411-goog

Re: [PATCH v11 15/46] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion

[Sean Christopherson]

On Wed, Aug 26, 2026, Ackerley Tng wrote:
> Omit support for calling the arch hook to make private, since SNP, the only
> implementer of the arch make-private hook today, would actually prefer
> making private only just before faulting memory into the NPTs.
> 
> Calling the make-private arch hook would require iterating both bindings
> and the filemap to find the intersection of bindings and allocated
> folios.

Why would KVM need to iterate over the bindings?  Only the RMP needs to be updated,
whether or not the RMP is currently reachable is irrelevant, no?

Subsequent calls to kvm_arch_gmem_make_private() from kvm_gmem_get_pfn() would be
superfluous, but that's already possible, e.g. if an NPT mappings is removed for
whatever reason.

> On top of that, SNP would need to figure out whether to actually
> make private based on whether the memory is about to be faulted, or
> whether it is a conversion.

This is a non-issue, no?  As above, sev_gmem_make_private() already bails early
if the page is already assigned in the RMP.

I don't care terribly about how SNP handles this, but I do want accurate reasoning
and justification so that if/when we revisit any of this in the future, we can make
informed decisions.  Because unless I'm missing something, this is an optimization
choice (eager vs. lazy to-private conversions), not a complexity tradeoff, and it's
not clear to me how we decided the lazy approach would provide better performance.

> Calling the make-shared arch hook and not the make-private arch hook does
> leak SNP-specific details into guest_memfd (as in, why only make-shared
> during conversions but not make-private?), but the additional complexity is
> not worth taking on until guest_memfd has a user actually requiring an arch
> make-private call.

...

> +#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);

The real reason I responded...

Thinking about the Secure AVIC mess made me realize zapping NPTs for SNP VMs isn't
strictly necessary in this path.  The PFN isn't changing, just the attributes, and
that's (obviously) tracked in the RMP.  KVM doesn't need to zap SPTEs to induce a
fault, because the mismatched C-bit vs. RMP status will cause an #NPF(RMP), and
AFAICT kvm_mmu_page_fault() will do the right thing.  A misbehaving guest could
continue to access the shared data (assuming we stick with lazy conversions), but
that should be fine?  E.g. it's not really any different than implicit conversions.

In other words, couldn't we do this (as an on-top optimization)?  The only wrinkle
I can think of is that it could delay reconstituion of a hugepage, especially if
we opted for eager conversion (because the guest wouldn't hit #NPFs to trigger the
hugepage promotion).

diff --git arch/x86/kvm/mmu/mmu.c arch/x86/kvm/mmu/mmu.c
index 62f751952ad8..61f3e270ab61 100644
--- arch/x86/kvm/mmu/mmu.c
+++ arch/x86/kvm/mmu/mmu.c
@@ -1670,6 +1670,7 @@ static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm,
 
 bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
 {
+       unsigned long shared_private =  KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;
        bool flush = false;
 
        /*
@@ -1683,6 +1684,10 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
        lockdep_assert_once(kvm->mmu_invalidate_in_progress ||
                            lockdep_is_held(&kvm->slots_lock));
 
+       if (gmem_in_place_conversion && !kvm_has_mirrored_tdp(kvm) &&
+           ((range->attr_filter & shared_private) != shared_private))
+               return false;
+
        if (kvm_memslots_have_rmaps(kvm))
                flush = __kvm_rmap_zap_gfn_range(kvm, range->slot,
                                                 range->start, range->end,

Re: [PATCH v11 15/46] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion

[Michael Roth]

On Wed, Aug 26, 2026 at 12:44:40PM -0700, Sean Christopherson wrote:
> On Wed, Aug 26, 2026, Ackerley Tng wrote:
> > Omit support for calling the arch hook to make private, since SNP, the only
> > implementer of the arch make-private hook today, would actually prefer
> > making private only just before faulting memory into the NPTs.
> > 
> > Calling the make-private arch hook would require iterating both bindings
> > and the filemap to find the intersection of bindings and allocated
> > folios.
> 
> Why would KVM need to iterate over the bindings?  Only the RMP needs to be updated,
> whether or not the RMP is currently reachable is irrelevant, no?
> 
> Subsequent calls to kvm_arch_gmem_make_private() from kvm_gmem_get_pfn() would be
> superfluous, but that's already possible, e.g. if an NPT mappings is removed for
> whatever reason.
> 
> > On top of that, SNP would need to figure out whether to actually
> > make private based on whether the memory is about to be faulted, or
> > whether it is a conversion.
> 
> This is a non-issue, no?  As above, sev_gmem_make_private() already bails early
> if the page is already assigned in the RMP.
> 
> I don't care terribly about how SNP handles this, but I do want accurate reasoning
> and justification so that if/when we revisit any of this in the future, we can make
> informed decisions.  Because unless I'm missing something, this is an optimization
> choice (eager vs. lazy to-private conversions), not a complexity tradeoff, and it's
> not clear to me how we decided the lazy approach would provide better performance.

I'm not sure it was discussed in this context, but there was some past
discussion around preallocation (i.e. "should we call make-private arch
hooks at allocation time to allow for faster boot for prealloc guests"
and then that ran into the TDX side of things where that would
necessarily entail pre-mapping into the sEPT as well, so
KVM_PRE_FAULT_MEMORY ended up being the interface we adopted for this
purpose.

Since then, KVM_PRE_FAULT_MEMORY was added on the QEMU side and gets
called after all conversions for both SNP/TDX, and even without
preallocation it's a decent performance boost to SNP. If we were to
switch to pre-calling the make-private arch hook then the
KVM_PRE_FAULT_MEMORY call because partly redundant and in practice we'd
probably see a small performance loss.

So there's real performance differences here but it's sort of been
addressed through a solution that offers additional performance
benefits on top so there's no longer as much to be gained here I think.

But I guess that's a moot point...

> 
> > Calling the make-shared arch hook and not the make-private arch hook does
> > leak SNP-specific details into guest_memfd (as in, why only make-shared
> > during conversions but not make-private?), but the additional complexity is
> > not worth taking on until guest_memfd has a user actually requiring an arch
> > make-private call.
> 
> ...
> 
> > +#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);
> 
> The real reason I responded...
> 
> Thinking about the Secure AVIC mess made me realize zapping NPTs for SNP VMs isn't
> strictly necessary in this path.  The PFN isn't changing, just the attributes, and
> that's (obviously) tracked in the RMP.  KVM doesn't need to zap SPTEs to induce a
> fault, because the mismatched C-bit vs. RMP status will cause an #NPF(RMP), and
> AFAICT kvm_mmu_page_fault() will do the right thing.  A misbehaving guest could
> continue to access the shared data (assuming we stick with lazy conversions), but
> that should be fine?  E.g. it's not really any different than implicit conversions.

I think this should work in theory...

zapping NPTs means the vCPUs will keep retrying until they get the page first
vCPU that faulted is trying to grab from gmem. If we don't zap, then they will
instead be racing with the first vCPU, and if they lose they will be
generating implicit page faults that trigger conversions back to shared,
and most likely the first vCPU will re-trigger an implicit shared->private
conversion when it does PVALIDATE. Worst case, the guest fails PVALIDATE
due to racing with itself.

It's a bit chaotic, but it shouldn't break anything other than the guest, and
it's only something we'd generally expect for buggy/malicious guests anyway.

However...

> 
> In other words, couldn't we do this (as an on-top optimization)?  The only wrinkle
> I can think of is that it could delay reconstituion of a hugepage, especially if
> we opted for eager conversion (because the guest wouldn't hit #NPFs to trigger the
> hugepage promotion).
> 
> diff --git arch/x86/kvm/mmu/mmu.c arch/x86/kvm/mmu/mmu.c
> index 62f751952ad8..61f3e270ab61 100644
> --- arch/x86/kvm/mmu/mmu.c
> +++ arch/x86/kvm/mmu/mmu.c
> @@ -1670,6 +1670,7 @@ static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm,
>  
>  bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>  {
> +       unsigned long shared_private =  KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;
>         bool flush = false;
>  
>         /*
> @@ -1683,6 +1684,10 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>         lockdep_assert_once(kvm->mmu_invalidate_in_progress ||
>                             lockdep_is_held(&kvm->slots_lock));
>  
> +       if (gmem_in_place_conversion && !kvm_has_mirrored_tdp(kvm) &&
> +           ((range->attr_filter & shared_private) != shared_private))
> +               return false;
> +

This path would also trigger for hole-punching, where we would want to
zap the NPT entries. So we might need to adjust the logic for more than
just shared vs. private to account for that.

-Mike

>         if (kvm_memslots_have_rmaps(kvm))
>                 flush = __kvm_rmap_zap_gfn_range(kvm, range->slot,
>                                                  range->start, range->end,

Re: [PATCH v11 15/46] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion

[Sean Christopherson]

On Wed, Aug 26, 2026, Michael Roth wrote:
> On Wed, Aug 26, 2026 at 12:44:40PM -0700, Sean Christopherson wrote:
> > On Wed, Aug 26, 2026, Ackerley Tng wrote:
> > > Omit support for calling the arch hook to make private, since SNP, the only
> > > implementer of the arch make-private hook today, would actually prefer
> > > making private only just before faulting memory into the NPTs.
> > > 
> > > Calling the make-private arch hook would require iterating both bindings
> > > and the filemap to find the intersection of bindings and allocated
> > > folios.
> > 
> > Why would KVM need to iterate over the bindings?  Only the RMP needs to be updated,
> > whether or not the RMP is currently reachable is irrelevant, no?
> > 
> > Subsequent calls to kvm_arch_gmem_make_private() from kvm_gmem_get_pfn() would be
> > superfluous, but that's already possible, e.g. if an NPT mappings is removed for
> > whatever reason.
> > 
> > > On top of that, SNP would need to figure out whether to actually
> > > make private based on whether the memory is about to be faulted, or
> > > whether it is a conversion.
> > 
> > This is a non-issue, no?  As above, sev_gmem_make_private() already bails early
> > if the page is already assigned in the RMP.
> > 
> > I don't care terribly about how SNP handles this, but I do want accurate reasoning
> > and justification so that if/when we revisit any of this in the future, we can make
> > informed decisions.  Because unless I'm missing something, this is an optimization
> > choice (eager vs. lazy to-private conversions), not a complexity tradeoff, and it's
> > not clear to me how we decided the lazy approach would provide better performance.
> 
> I'm not sure it was discussed in this context, but there was some past
> discussion around preallocation (i.e. "should we call make-private arch
> hooks at allocation time to allow for faster boot for prealloc guests"
> and then that ran into the TDX side of things where that would
> necessarily entail pre-mapping into the sEPT as well, so
> KVM_PRE_FAULT_MEMORY ended up being the interface we adopted for this
> purpose.
> 
> Since then, KVM_PRE_FAULT_MEMORY was added on the QEMU side and gets
> called after all conversions for both SNP/TDX, and even without
> preallocation it's a decent performance boost to SNP. If we were to
> switch to pre-calling the make-private arch hook then the
> KVM_PRE_FAULT_MEMORY call because partly redundant and in practice we'd
> probably see a small performance loss.
> 
> So there's real performance differences here but it's sort of been
> addressed through a solution that offers additional performance
> benefits on top so there's no longer as much to be gained here I think.

Or another way to look at it, eager conversion would allow QEMU to drop its
workaround.

To be clear, I'm a-ok with the code as-is, I just want to make sure we document
exactly why we're choosing this implementation.

> But I guess that's a moot point...
> 
> > 
> > > Calling the make-shared arch hook and not the make-private arch hook does
> > > leak SNP-specific details into guest_memfd (as in, why only make-shared
> > > during conversions but not make-private?), but the additional complexity is
> > > not worth taking on until guest_memfd has a user actually requiring an arch
> > > make-private call.
> > 
> > ...
> > 
> > > +#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);
> > 
> > The real reason I responded...
> > 
> > Thinking about the Secure AVIC mess made me realize zapping NPTs for SNP VMs isn't
> > strictly necessary in this path.  The PFN isn't changing, just the attributes, and
> > that's (obviously) tracked in the RMP.  KVM doesn't need to zap SPTEs to induce a
> > fault, because the mismatched C-bit vs. RMP status will cause an #NPF(RMP), and
> > AFAICT kvm_mmu_page_fault() will do the right thing.  A misbehaving guest could
> > continue to access the shared data (assuming we stick with lazy conversions), but
> > that should be fine?  E.g. it's not really any different than implicit conversions.
> 
> I think this should work in theory...
> 
> zapping NPTs means the vCPUs will keep retrying until they get the page first
> vCPU that faulted is trying to grab from gmem. If we don't zap, then they will
> instead be racing with the first vCPU, and if they lose they will be
> generating implicit page faults that trigger conversions back to shared,

Why would they trigger conversions back to shared?  Assuming the guest isn't
being silly and accessing the memory with C-bit=0, the #NPF will be tagged ENC
and KVM will treat it as a private access.

	if (is_sev_snp_guest(vcpu) && (error_code & PFERR_GUEST_ENC_MASK))
		error_code |= PFERR_PRIVATE_ACCESS;

kvm_mmu_faultin_pfn() will see "fault->is_private == kvm_is_private_gfn()" as
true, i.e. won't kick out to userspace.  Same for __kvm_mmu_faultin_pfn(), which
will call into kvm_mmu_faultin_pfn_gmem() => kvm_gmem_get_pfn(), see that the
gfn is private, and call kvm_arch_gmem_make_private() as needed.

I don't see how #NPFs due to the RMP being SHARED would be handled differently
than !PRESENT #NPFs.

> and most likely the first vCPU will re-trigger an implicit shared->private
> conversion when it does PVALIDATE. Worst case, the guest fails PVALIDATE
> due to racing with itself.
> 
> It's a bit chaotic, but it shouldn't break anything other than the guest, and
> it's only something we'd generally expect for buggy/malicious guests anyway.
> 
> However...
> 
> > 
> > In other words, couldn't we do this (as an on-top optimization)?  The only wrinkle
> > I can think of is that it could delay reconstituion of a hugepage, especially if
> > we opted for eager conversion (because the guest wouldn't hit #NPFs to trigger the
> > hugepage promotion).
> > 
> > diff --git arch/x86/kvm/mmu/mmu.c arch/x86/kvm/mmu/mmu.c
> > index 62f751952ad8..61f3e270ab61 100644
> > --- arch/x86/kvm/mmu/mmu.c
> > +++ arch/x86/kvm/mmu/mmu.c
> > @@ -1670,6 +1670,7 @@ static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm,
> >  
> >  bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
> >  {
> > +       unsigned long shared_private =  KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;
> >         bool flush = false;
> >  
> >         /*
> > @@ -1683,6 +1684,10 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
> >         lockdep_assert_once(kvm->mmu_invalidate_in_progress ||
> >                             lockdep_is_held(&kvm->slots_lock));
> >  
> > +       if (gmem_in_place_conversion && !kvm_has_mirrored_tdp(kvm) &&
> > +           ((range->attr_filter & shared_private) != shared_private))
> > +               return false;
> > +
> 
> This path would also trigger for hole-punching, where we would want to
> zap the NPT entries. So we might need to adjust the logic for more than
> just shared vs. private to account for that.

No, because PUNCH_HOLE uses kvm_gmem_get_all_gfns_filter(), which does:

	if (gmem_in_place_conversion)
		return KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;

i.e. won't get short-circuited.  Though I agree with the implication that this
is super fragile/subtle.

Re: [PATCH v11 15/46] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion

[Michael Roth]

On Wed, Aug 26, 2026 at 03:33:43PM -0700, Sean Christopherson wrote:
> On Wed, Aug 26, 2026, Michael Roth wrote:
> > On Wed, Aug 26, 2026 at 12:44:40PM -0700, Sean Christopherson wrote:
> > > On Wed, Aug 26, 2026, Ackerley Tng wrote:
> > > > Omit support for calling the arch hook to make private, since SNP, the only
> > > > implementer of the arch make-private hook today, would actually prefer
> > > > making private only just before faulting memory into the NPTs.
> > > > 
> > > > Calling the make-private arch hook would require iterating both bindings
> > > > and the filemap to find the intersection of bindings and allocated
> > > > folios.
> > > 
> > > Why would KVM need to iterate over the bindings?  Only the RMP needs to be updated,
> > > whether or not the RMP is currently reachable is irrelevant, no?
> > > 
> > > Subsequent calls to kvm_arch_gmem_make_private() from kvm_gmem_get_pfn() would be
> > > superfluous, but that's already possible, e.g. if an NPT mappings is removed for
> > > whatever reason.
> > > 
> > > > On top of that, SNP would need to figure out whether to actually
> > > > make private based on whether the memory is about to be faulted, or
> > > > whether it is a conversion.
> > > 
> > > This is a non-issue, no?  As above, sev_gmem_make_private() already bails early
> > > if the page is already assigned in the RMP.
> > > 
> > > I don't care terribly about how SNP handles this, but I do want accurate reasoning
> > > and justification so that if/when we revisit any of this in the future, we can make
> > > informed decisions.  Because unless I'm missing something, this is an optimization
> > > choice (eager vs. lazy to-private conversions), not a complexity tradeoff, and it's
> > > not clear to me how we decided the lazy approach would provide better performance.
> > 
> > I'm not sure it was discussed in this context, but there was some past
> > discussion around preallocation (i.e. "should we call make-private arch
> > hooks at allocation time to allow for faster boot for prealloc guests"
> > and then that ran into the TDX side of things where that would
> > necessarily entail pre-mapping into the sEPT as well, so
> > KVM_PRE_FAULT_MEMORY ended up being the interface we adopted for this
> > purpose.
> > 
> > Since then, KVM_PRE_FAULT_MEMORY was added on the QEMU side and gets
> > called after all conversions for both SNP/TDX, and even without
> > preallocation it's a decent performance boost to SNP. If we were to
> > switch to pre-calling the make-private arch hook then the
> > KVM_PRE_FAULT_MEMORY call because partly redundant and in practice we'd
> > probably see a small performance loss.
> > 
> > So there's real performance differences here but it's sort of been
> > addressed through a solution that offers additional performance
> > benefits on top so there's no longer as much to be gained here I think.
> 
> Or another way to look at it, eager conversion would allow QEMU to drop its
> workaround.

True, for SNP at least, but pre-map is nice too, and not really gmem's
place, so most likely KVM_PRE_FAULT_MEMORY would remain regardless.

> 
> To be clear, I'm a-ok with the code as-is, I just want to make sure we document
> exactly why we're choosing this implementation.

Agreed. My understanding of the current design choice is basically that
it doesn't *need* to happen here, since kvm_gmem_get_pfn() will already
trigger it on-demand when it is actually needed (or not), and that tends
to happen at fault time when other platforms like TDX handle it. To handle
it differently would be to go out of our way to make SNP special in this
flow in exchange for performance, but KVM_PRE_FAULT_MEMORY already offers
a robust solution for folks that want to optimize conversion path or
prealloc host resources prior to guest boot.

> 
> > But I guess that's a moot point...
> > 
> > > 
> > > > Calling the make-shared arch hook and not the make-private arch hook does
> > > > leak SNP-specific details into guest_memfd (as in, why only make-shared
> > > > during conversions but not make-private?), but the additional complexity is
> > > > not worth taking on until guest_memfd has a user actually requiring an arch
> > > > make-private call.
> > > 
> > > ...
> > > 
> > > > +#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);
> > > 
> > > The real reason I responded...
> > > 
> > > Thinking about the Secure AVIC mess made me realize zapping NPTs for SNP VMs isn't
> > > strictly necessary in this path.  The PFN isn't changing, just the attributes, and
> > > that's (obviously) tracked in the RMP.  KVM doesn't need to zap SPTEs to induce a
> > > fault, because the mismatched C-bit vs. RMP status will cause an #NPF(RMP), and
> > > AFAICT kvm_mmu_page_fault() will do the right thing.  A misbehaving guest could
> > > continue to access the shared data (assuming we stick with lazy conversions), but
> > > that should be fine?  E.g. it's not really any different than implicit conversions.
> > 
> > I think this should work in theory...
> > 
> > zapping NPTs means the vCPUs will keep retrying until they get the page first
> > vCPU that faulted is trying to grab from gmem. If we don't zap, then they will
> > instead be racing with the first vCPU, and if they lose they will be
> > generating implicit page faults that trigger conversions back to shared,
> 
> Why would they trigger conversions back to shared?  Assuming the guest isn't
> being silly and accessing the memory with C-bit=0, the #NPF will be tagged ENC

I wasn't meaning the normal flow for a well-behaved guest, but when you
mentioned "mismatched C-bit vs. RMP status will cause an #NPF(RMP)" I
thought you were considering the case of multiple vCPUs accessing the
same GPA in various ways (that may or may not make sense) and whether not
zapping before conversion would cause any issues with the handling of that
scenario. In that scenario there is potential for any mix of mismatches
between C-bits and RMP tables.

The silly case with C=0 is the specific scenario I was thinking of. E.g.
one vCPU is trying to due memory acceptance/PVALIDATE of a GPA that's
somehow still being used by some other vCPU for some shared memory
workload.

> and KVM will treat it as a private access.
> 
> 	if (is_sev_snp_guest(vcpu) && (error_code & PFERR_GUEST_ENC_MASK))
> 		error_code |= PFERR_PRIVATE_ACCESS;
> 
> kvm_mmu_faultin_pfn() will see "fault->is_private == kvm_is_private_gfn()" as
> true, i.e. won't kick out to userspace.  Same for __kvm_mmu_faultin_pfn(), which
> will call into kvm_mmu_faultin_pfn_gmem() => kvm_gmem_get_pfn(), see that the
> gfn is private, and call kvm_arch_gmem_make_private() as needed.

Yes I don't see any issue with the normal/well-behaved path, it's just
the funky edge-cases that seem bring about some new considerations, but
it seems like those would be handled okay.

> 
> I don't see how #NPFs due to the RMP being SHARED would be handled differently
> than !PRESENT #NPFs.
> 
> > and most likely the first vCPU will re-trigger an implicit shared->private
> > conversion when it does PVALIDATE. Worst case, the guest fails PVALIDATE
> > due to racing with itself.
> > 
> > It's a bit chaotic, but it shouldn't break anything other than the guest, and
> > it's only something we'd generally expect for buggy/malicious guests anyway.
> > 
> > However...
> > 
> > > 
> > > In other words, couldn't we do this (as an on-top optimization)?  The only wrinkle
> > > I can think of is that it could delay reconstituion of a hugepage, especially if
> > > we opted for eager conversion (because the guest wouldn't hit #NPFs to trigger the
> > > hugepage promotion).
> > > 
> > > diff --git arch/x86/kvm/mmu/mmu.c arch/x86/kvm/mmu/mmu.c
> > > index 62f751952ad8..61f3e270ab61 100644
> > > --- arch/x86/kvm/mmu/mmu.c
> > > +++ arch/x86/kvm/mmu/mmu.c
> > > @@ -1670,6 +1670,7 @@ static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm,
> > >  
> > >  bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
> > >  {
> > > +       unsigned long shared_private =  KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;
> > >         bool flush = false;
> > >  
> > >         /*
> > > @@ -1683,6 +1684,10 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
> > >         lockdep_assert_once(kvm->mmu_invalidate_in_progress ||
> > >                             lockdep_is_held(&kvm->slots_lock));
> > >  
> > > +       if (gmem_in_place_conversion && !kvm_has_mirrored_tdp(kvm) &&
> > > +           ((range->attr_filter & shared_private) != shared_private))
> > > +               return false;
> > > +
> > 
> > This path would also trigger for hole-punching, where we would want to
> > zap the NPT entries. So we might need to adjust the logic for more than
> > just shared vs. private to account for that.
> 
> No, because PUNCH_HOLE uses kvm_gmem_get_all_gfns_filter(), which does:
> 
> 	if (gmem_in_place_conversion)
> 		return KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;

Doh, helps if I actually have the right branch checkout out when looking at
code. That does look to be covered.

I'll give this patch a spin on my end as well and report back if I notice
any crazyness.

Thanks,

Mike

> 
> i.e. won't get short-circuited.  Though I agree with the implication that this
> is super fragile/subtle.
> 

[PATCH v11 16/46] KVM: guest_memfd: Return early if range already has requested attributes

[Ackerley Tng]

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 d1134b23576e4..6dc199be0eb87 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) {

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 17/46] mm/gup: factor out LRU cache draining for folio into lru_cache_drain_for_folio()

[Ackerley Tng]

From: "David Hildenbrand (Arm)" <david@kernel.org>

KVM with guest_memfd wants to remove any folio references due to LRU
caches, as it really must only allow to convert folios from shared to
private when there are no unexpected folio references (e.g., from GUP
references).

So, to drive the refcount down, it needs a way to flush the LRU caches.
Let's factor out what we have in lru_cache_drain_for_folio(). Document
it, and also mention that concurrent folio (un)mapping might, in theory,
miss detecting LRU cache references. Keep obtaining the expected refcount
twice to minimize the possibility. For the current and future user that
should work, and we don't really have a better alternative: we could
detect if the mapcount changed, but it would still be racy and add more
complexity with questionable benefit.

Maybe there is a chance to avoid the draining entirely in the future,
by avoiding extra references from the LRU cache: Hugh thinks there might
be a way. But for the time being, this handling is unfortunately
required.

Make folio_may_be_lru_cached() accept a const pointer so
lru_cache_drain_for_folio() can accept a const pointer as well.

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 include/linux/swap.h | 11 ++++++++++-
 mm/gup.c             | 20 +++++++-------------
 mm/swap.c            | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 14 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 8f0f68e245baa..e625d64c9e13d 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -317,7 +317,7 @@ void folio_add_lru_vma(struct folio *, struct vm_area_struct *);
 void mark_page_accessed(struct page *);
 void folio_mark_accessed(struct folio *);
 
-static inline bool folio_may_be_lru_cached(struct folio *folio)
+static inline bool folio_may_be_lru_cached(const struct folio *folio)
 {
 	/*
 	 * Holding PMD-sized folios in per-CPU LRU cache unbalances accounting.
@@ -344,6 +344,15 @@ extern void lru_add_drain(void);
 extern void lru_add_drain_cpu(int cpu);
 extern void lru_add_drain_cpu_zone(struct zone *zone);
 extern void lru_add_drain_all(void);
+
+enum lru_cache_drained {
+	LRU_CACHE_NOT_DRAINED,
+	LRU_CACHE_DRAINED,
+	LRU_CACHE_DRAINED_ALL,
+};
+void lru_cache_drain_for_folio(const struct folio *folio,
+		unsigned int extra_refs, enum lru_cache_drained *drained);
+
 void folio_deactivate(struct folio *folio);
 void folio_mark_lazyfree(struct folio *folio);
 extern void swap_setup(void);
diff --git a/mm/gup.c b/mm/gup.c
index 0692119b79043..fb0995dc495fc 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2266,9 +2266,9 @@ static unsigned long collect_longterm_unpinnable_folios(
 		struct list_head *movable_folio_list,
 		struct pages_or_folios *pofs)
 {
+	enum lru_cache_drained drained = LRU_CACHE_NOT_DRAINED;
 	unsigned long collected = 0;
 	struct folio *folio;
-	int drained = 0;
 	long i = 0;
 
 	for (folio = pofs_get_folio(pofs, i); folio;
@@ -2287,18 +2287,12 @@ static unsigned long collect_longterm_unpinnable_folios(
 			continue;
 		}
 
-		if (drained == 0 && folio_may_be_lru_cached(folio) &&
-				folio_ref_count(folio) !=
-				folio_expected_ref_count(folio) + 1) {
-			lru_add_drain();
-			drained = 1;
-		}
-		if (drained == 1 && folio_may_be_lru_cached(folio) &&
-				folio_ref_count(folio) !=
-				folio_expected_ref_count(folio) + 1) {
-			lru_add_drain_all();
-			drained = 2;
-		}
+		/*
+		 * We drain not only to make the folio_isolate_lru() succeed,
+		 * but also to remove any other folio references from LRU
+		 * caches.
+		 */
+		lru_cache_drain_for_folio(folio, 1, &drained);
 
 		if (!folio_isolate_lru(folio))
 			continue;
diff --git a/mm/swap.c b/mm/swap.c
index 588f50d8f1a8c..8e965c8ce9aa9 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -950,6 +950,52 @@ void lru_add_drain_all(void)
 }
 #endif /* CONFIG_SMP */
 
+/**
+ * lru_cache_drain_for_folio() - drain LRU caches if the caches might hold
+ *				 folio references
+ * @folio: The folio.
+ * @extra_refs: Extra folio references held by the caller.
+ * @drained: Drain status for batch folio processing.
+ *
+ * Drain LRU caches if the caches might hold folio references. Start
+ * with a local LRU cache drain, to then drain LRU caches on all CPUs if
+ * local draining was insufficient.
+ *
+ * This function detects LRU cache references by comparing the folio refcount
+ * with the sum of the expected folio refcount + extra references held by the
+ * caller. Note that we cannot rely on PG_lru to reliably detect all LRU
+ * cache references, and there are rare scenarios (concurrent folio (un)mapping)
+ * where this function might miss detecting LRU cache references.
+ *
+ * If @drained is not NULL, the function will avoid re-draining LRU caches
+ * when processing multiple folios in a row. In that case, the variable
+ * @drained points at must be initialized to LRU_CACHE_NOT_DRAINED before
+ * the first invocation by the caller.
+ */
+void lru_cache_drain_for_folio(const struct folio *folio,
+		unsigned int extra_refs, enum lru_cache_drained *drained)
+{
+	if (!folio_may_be_lru_cached(folio))
+		return;
+
+	if (!drained || *drained == LRU_CACHE_NOT_DRAINED) {
+		if (folio_ref_count(folio) ==
+		    folio_expected_ref_count(folio) + extra_refs)
+			return;
+		lru_add_drain();
+		if (drained)
+			*drained = LRU_CACHE_DRAINED;
+	}
+	if (!drained || *drained == LRU_CACHE_DRAINED) {
+		if (folio_ref_count(folio) ==
+		    folio_expected_ref_count(folio) + extra_refs)
+			return;
+		lru_add_drain_all();
+		if (drained)
+			*drained = LRU_CACHE_DRAINED_ALL;
+	}
+}
+
 atomic_t lru_disable_count = ATOMIC_INIT(0);
 
 /*

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 18/46] KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check

[Ackerley Tng]

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/swap.c              |  2 ++
 virt/kvm/guest_memfd.c | 30 ++++++++++++++++++++++--------
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index 8e965c8ce9aa9..9f511b97ab110 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -37,6 +37,7 @@
 #include <linux/page_idle.h>
 #include <linux/local_lock.h>
 #include <linux/buffer_head.h>
+#include <linux/kvm_types.h>
 
 #include "internal.h"
 
@@ -995,6 +996,7 @@ 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 6dc199be0eb87..4912f90567fe8 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;
 			}

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 19/46] KVM: guest_memfd: Zero page while getting pfn

[Ackerley Tng]

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 4912f90567fe8..9c2d52bdf25ec 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);

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 20/46] KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE

[Ackerley Tng]

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
 
 /*

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 21/46] KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION

[Ackerley Tng]

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--;
 

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 22/46] KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86

[Ackerley Tng]

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

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 23/46] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes

[Ackerley Tng]

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 +++++++++++++++++++++++++
 Documentation/virt/kvm/api.rst                  |  7 +++++--
 arch/x86/include/asm/kvm_host.h                 |  4 +++-
 arch/x86/kvm/Kconfig                            | 14 ++++++++++----
 virt/kvm/kvm_main.c                             |  5 ++++-
 5 files changed, 47 insertions(+), 8 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1069806616b94..0ac44e1bccd28 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3114,6 +3114,31 @@ 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/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index f88d65b78c504..d976f8ec2e2dc 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6383,9 +6383,12 @@ 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 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
+state.  If in-place conversion is disabled, i.e. PRIVATE is tracked per-VM,
+then 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
 toggling KVM_MEMORY_ATTRIBUTE_PRIVATE via KVM_SET_MEMORY_ATTRIBUTES as needed.
+If in-place conversion is enabled, then the starting PRIVATE vs. SHARED state
+of a gfn is determined by the relevant guest_memfd instance.
 
 S390:
 ^^^^^
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
 

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 24/46] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs

[Ackerley Tng]

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 147b3e529cd26..45ef4156274ec 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

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 25/46] KVM: selftests: Create gmem fd before "regular" fd when adding memslot

[Ackerley Tng]

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();

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 26/46] KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset}

[Ackerley Tng]

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;
 	}

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 27/46] KVM: selftests: Add support for mmap() on guest_memfd in core library

[Ackerley Tng]

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;

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 28/46] KVM: selftests: Add selftests global for guest memory attributes capability

[Ackerley Tng]

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();
 }
 

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 29/46] KVM: selftests: Add helpers for calling ioctls on guest_memfd

[Ackerley Tng]

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);
 

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 30/46] KVM: selftests: Test basic single-page conversion flow

[Ackerley Tng]

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);
+}

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 31/46] KVM: selftests: Test conversion flow when INIT_SHARED

[Ackerley Tng]

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));

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 32/46] KVM: selftests: Test conversion precision in guest_memfd

[Ackerley Tng]

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));

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 33/46] KVM: selftests: Test conversion before allocation

[Ackerley Tng]

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));

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 34/46] KVM: selftests: Convert with allocated folios in different layouts

[Ackerley Tng]

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));

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 35/46] KVM: selftests: Test that truncation does not change shared/private status

[Ackerley Tng]

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));

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 36/46] KVM: selftests: Test that shared/private status is consistent across processes

[Ackerley Tng]

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));

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 37/46] KVM: selftests: Add helpers to pin pages with CONFIG_GUP_TEST

[Ackerley Tng]

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);

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 38/46] KVM: selftests: Test conversion with elevated page refcount

[Ackerley Tng]

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));

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 39/46] KVM: selftests: Reset shared memory after hole-punching

[Ackerley Tng]

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);
 	}
 }
 

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 40/46] KVM: selftests: Provide function to look up guest_memfd details from gpa

[Ackerley Tng]

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;
+		fd = kvm_gpa_to_guest_memfd(vm, gpa, &fd_offset, &len);
+		len = min(end - gpa, len);
 
-		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);
-
-		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)
 {

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 41/46] KVM: selftests: Provide common function to set memory attributes

[Ackerley Tng]

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);
 

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 42/46] KVM: selftests: Make TEST_EXPECT_SIGBUS thread-safe

[Ackerley Tng]

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 | 30 +++++++++++++------------
 tools/testing/selftests/kvm/lib/kvm_util.c      | 18 ++++++++++-----
 tools/testing/selftests/kvm/lib/test_util.c     |  7 ------
 3 files changed, 29 insertions(+), 26 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);
+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_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);					\
+#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.

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 43/46] KVM: selftests: Support guest_memfd attributes in private_mem_conversions_test

[Ackerley Tng]

Update private_mem_conversions_test to support environments where
guest_memfd tracks memory attributes.

At guest_memfd setup time, 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.

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.

Suggested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../selftests/kvm/x86/private_mem_conversions_test.c   | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 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..0c94e36575a5e 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;
 }
 
@@ -383,6 +386,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_v
 	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 +401,16 @@ 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_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;

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 44/46] KVM: selftests: Set up page size and alignment independently for guest_memfd

[Ackerley Tng]

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;

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 45/46] KVM: selftests: Test in-place conversions in private_mem_conversions_test

[Ackerley Tng]

Test in-place conversions by setting up the guest with a single backing,
using the same guest_memfd for both private and shared memory.

Make testing single backing the default when per-guest_memfd memory
attributes are supported (kvm_has_gmem_attributes). Continue to support
testing of double-backing by accepting a -2 flag.

When testing single-backing, 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.

To test in-place conversions, set up guest_memfd with
GUEST_MEMFD_FLAG_MMAP and GUEST_MEMFD_FLAG_INIT_SHARED so that both host
and guest access the same backing physical memory.

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         | 55 +++++++++++++++++-----
 1 file changed, 44 insertions(+), 11 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 0c94e36575a5e..8f03eea9e2fb6 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -26,6 +26,8 @@
 #define BASE_DATA_GPA		((u64)(1ull << 32))
 #define PER_CPU_DATA_SIZE	((u64)(SZ_2M + PAGE_SIZE))
 
+static bool use_double_backing;
+
 /* Horrific macro so that the line info is captured accurately :-( */
 #define memcmp_g(gpa, pattern,  size)								\
 do {												\
@@ -355,8 +357,15 @@ 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);
+				/*
+				 * When using double backing, the host should
+				 * always observe shared data, since the shared
+				 * memory is a separate page.
+				 */
+				if (use_double_backing)
+					memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
+				else if (uc.args[0] == SYNC_PRIVATE)
+					TEST_EXPECT_SIGBUS(READ_ONCE(*hva));
 
 				/* For shared, write the new pattern to guest memory. */
 				if (uc.args[0] == SYNC_SHARED)
@@ -372,15 +381,23 @@ 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 (use_double_backing)
+		alignment = get_backing_src_pagesz(src_type);
+	else
+		alignment = getpagesize();
+
+	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];
@@ -404,6 +421,8 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_v
 	gmem_flags = 0;
 	if (kvm_has_gmem_attributes)
 		gmem_flags |= GUEST_MEMFD_FLAG_INIT_SHARED;
+	if (!use_double_backing)
+		gmem_flags |= GUEST_MEMFD_FLAG_MMAP;
 
 	memfd = vm_create_guest_memfd(vm, memfd_size, gmem_flags);
 
@@ -448,7 +467,9 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_v
 static void usage(const char *cmd)
 {
 	puts("");
-	printf("usage: %s [-h] [-m nr_memslots] [-s mem_type] [-n nr_vcpus]\n", cmd);
+	printf("usage: %s [-2] [-h] [-m nr_memslots] [-s mem_type] [-n nr_vcpus]\n", cmd);
+	puts("");
+	puts(" -2: use double backing (guest_memfd for private, src_type for shared)");
 	puts("");
 	backing_src_help("-s");
 	puts("");
@@ -461,16 +482,22 @@ static void usage(const char *cmd)
 int main(int argc, char *argv[])
 {
 	enum vm_mem_backing_src_type src_type = DEFAULT_VM_MEM_SRC;
+	const char *backing_src_str = NULL;
 	u32 nr_memslots = 1;
 	u32 nr_vcpus = 1;
 	int opt;
 
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
 
-	while ((opt = getopt(argc, argv, "hm:s:n:")) != -1) {
+	use_double_backing = !kvm_has_gmem_attributes;
+
+	while ((opt = getopt(argc, argv, "2hm:s:n:")) != -1) {
 		switch (opt) {
+		case '2':
+			use_double_backing = true;
+			break;
 		case 's':
-			src_type = parse_backing_src_type(optarg);
+			backing_src_str = optarg;
 			break;
 		case 'n':
 			nr_vcpus = atoi_positive("nr_vcpus", optarg);
@@ -485,6 +512,12 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (backing_src_str) {
+		TEST_ASSERT(use_double_backing,
+			    "src_type is only configurable when testing using double backing.");
+		src_type = parse_backing_src_type(backing_src_str);
+	}
+
 	test_mem_conversions(src_type, nr_vcpus, nr_memslots);
 
 	return 0;

-- 
2.55.0.887.g758fc8c411-goog

[PATCH v11 46/46] KVM: selftests: Update private memory exits test to work with per-gmem attributes

[Ackerley Tng]

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);
 

-- 
2.55.0.887.g758fc8c411-goog