* [PATCH v10 01/41] KVM: guest_memfd: Use kvm_mem_is_private() when populating guest_memfd memory
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 02/41] KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings Ackerley Tng via B4 Relay
` (39 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
From: Sean Christopherson <seanjc@google.com>
Using 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.
Suggested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
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 b596486d184ca..a11cf6dc785da 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -811,9 +811,7 @@ 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;
}
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 02/41] KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 01/41] KVM: guest_memfd: Use kvm_mem_is_private() when populating guest_memfd memory Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 03/41] KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES Ackerley Tng via B4 Relay
` (38 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
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).
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>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
virt/kvm/guest_memfd.c | 133 ++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 116 insertions(+), 17 deletions(-)
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index a11cf6dc785da..1f1ae61b4878b 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 +69,25 @@ 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_attributes(struct inode *inode, void *entry)
+{
+ if (WARN_ON_ONCE(!entry)) {
+ bool initially_shared = GMEM_I(inode)->flags &
+ GUEST_MEMFD_FLAG_INIT_SHARED;
+
+ return initially_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
+ }
+
+ 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 +388,13 @@ 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 +547,51 @@ 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 = gi->flags & GUEST_MEMFD_FLAG_INIT_SHARED ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
+
+ /*
+ * 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 +622,9 @@ 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)) {
@@ -764,9 +829,13 @@ 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));
@@ -786,6 +855,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
else
folio_put(folio);
+out:
+ filemap_invalidate_unlock_shared(file_inode(file)->i_mapping);
return r;
}
EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn);
@@ -915,6 +986,15 @@ 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;
@@ -922,7 +1002,26 @@ 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)
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 03/41] KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 01/41] KVM: guest_memfd: Use kvm_mem_is_private() when populating guest_memfd memory Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 02/41] KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 04/41] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined Ackerley Tng via B4 Relay
` (37 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
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 283847619ff88..14d86851fce78 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
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 c519e8e8d646f..acafa7964964c 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -8070,7 +8070,7 @@ 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 d94b59140c452..f1d977060489b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10134,7 +10134,7 @@ 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 03bfc92864b6e..3e86cdd00e59b 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 f3a6ba740ff79..e3a77d1e6d8ae 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;
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 04/41] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (2 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 03/41] KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 05/41] KVM: Rename memory attribute APIs to prepare for in-place gmem conversion Ackerley Tng via B4 Relay
` (36 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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>
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 3e86cdd00e59b..e3666d0b40b74 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 e3a77d1e6d8ae..560ff05e95959 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;
}
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 05/41] KVM: Rename memory attribute APIs to prepare for in-place gmem conversion
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (3 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 04/41] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 06/41] KVM: Provide generic interface for checking memory private/shared status Ackerley Tng via B4 Relay
` (35 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
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>
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 acafa7964964c..2b3bc73845a8a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -8089,8 +8089,8 @@ 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;
@@ -8159,18 +8159,18 @@ 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;
@@ -8263,7 +8263,7 @@ 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 e3666d0b40b74..3464a0ddbae74 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 560ff05e95959..b3f9396123be2 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:
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 06/41] KVM: Provide generic interface for checking memory private/shared status
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (4 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 05/41] KVM: Rename memory attribute APIs to prepare for in-place gmem conversion Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 07/41] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion Ackerley Tng via B4 Relay
` (34 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
From: Sean Christopherson <seanjc@google.com>
Introduce a generic kvm_mem_is_private() 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_mem_is_private 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>
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 3464a0ddbae74..65fbce46b63f4 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_mem_is_private(struct kvm *kvm, gfn_t gfn)
+static inline bool kvm_vm_mem_is_private(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_mem_is_private_t)(struct kvm *kvm, gfn_t gfn);
+DECLARE_STATIC_CALL(__kvm_mem_is_private, kvm_mem_is_private_t);
+
+static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+{
+ return static_call(__kvm_mem_is_private)(kvm, gfn);
+}
#else
static inline bool kvm_mem_is_private(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 b3f9396123be2..a01d336eab18b 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_mem_is_private, kvm_mem_is_private_t);
+EXPORT_STATIC_CALL_GPL(__kvm_mem_is_private);
+
+static void kvm_init_memory_attributes(void)
+{
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+ static_call_update(__kvm_mem_is_private, kvm_vm_mem_is_private);
+#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);
@@ -6547,6 +6561,7 @@ 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();
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 07/41] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (5 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 06/41] KVM: Provide generic interface for checking memory private/shared status Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 08/41] KVM: Consolidate private memory and guest_memfd ifdeffery in kvm_host.h Ackerley Tng via B4 Relay
` (33 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
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_mem_is_private() 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 65fbce46b63f4..9477ecebbbced 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2580,6 +2580,8 @@ static inline bool kvm_vm_mem_is_private(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_mem_is_private_t)(struct kvm *kvm, gfn_t gfn);
DECLARE_STATIC_CALL(__kvm_mem_is_private, kvm_mem_is_private_t);
@@ -2588,6 +2590,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
return static_call(__kvm_mem_is_private)(kvm, gfn);
}
#else
+#define gmem_in_place_conversion false
+
static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
{
return false;
@@ -2595,6 +2599,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
#endif /* kvm_arch_has_private_mem */
#ifdef CONFIG_KVM_GUEST_MEMFD
+bool kvm_gmem_is_private(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, struct page **page,
int *max_order);
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 1f1ae61b4878b..75979c885e030 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -475,6 +475,32 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma)
return 0;
}
+bool kvm_gmem_is_private(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);
+
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 a01d336eab18b..0a5a1bee8de0f 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_mem_is_private);
static void kvm_init_memory_attributes(void)
{
+ if (gmem_in_place_conversion)
+ static_call_update(__kvm_mem_is_private, kvm_gmem_is_private);
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
- static_call_update(__kvm_mem_is_private, kvm_vm_mem_is_private);
+ else
+ static_call_update(__kvm_mem_is_private, kvm_vm_mem_is_private);
#endif
}
#else
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 08/41] KVM: Consolidate private memory and guest_memfd ifdeffery in kvm_host.h
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (6 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 07/41] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 09/41] KVM: guest_memfd: Filter both shared and private when invalidating Ackerley Tng via B4 Relay
` (32 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
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>
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 9477ecebbbced..dfdb3c97a7ac9 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_mem_is_private(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_mem_is_private(struct kvm *kvm, gfn_t gfn)
{
return false;
@@ -2600,6 +2584,17 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
#ifdef CONFIG_KVM_GUEST_MEMFD
bool kvm_gmem_is_private(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, struct page **page,
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 09/41] KVM: guest_memfd: Filter both shared and private when invalidating
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (7 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 08/41] KVM: Consolidate private memory and guest_memfd ifdeffery in kvm_host.h Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 10/41] KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2 Ackerley Tng via B4 Relay
` (31 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Before conversion, a guest_memfd could be either all shared, or all
private, configured at creation time using the INIT_SHARED flag. Hence,
when zapping pages from stage 2 page tables, guest_memfd can filter which
to zap based on the initial shared/private state.
With conversion, guest_memfd tracks shared/private state on a per-page
level, so a range can contain both private and shared pages. Zap both
private and shared pages for simplicity.
An alternative would be to iterate guest_memfd attributes and only zap both
if shared and private pages exist within the range. Setting both the shared
and private filters lets the zapping logic do that iteration instead.
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
virt/kvm/guest_memfd.c | 24 ++++++++----------------
1 file changed, 8 insertions(+), 16 deletions(-)
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 75979c885e030..b1537226e5adf 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -136,14 +136,6 @@ 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)
-{
- if (GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED)
- return KVM_FILTER_SHARED;
-
- return KVM_FILTER_PRIVATE;
-}
-
static void __kvm_gmem_invalidate_start(struct gmem_file *f, pgoff_t start,
pgoff_t end,
enum kvm_gfn_range_filter attr_filter)
@@ -186,15 +178,13 @@ 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;
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);
+ __kvm_gmem_invalidate_start(f, start, end, filter);
}
static void __kvm_gmem_invalidate_end(struct gmem_file *f, pgoff_t start,
@@ -229,7 +219,8 @@ 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,
+ KVM_FILTER_SHARED | KVM_FILTER_PRIVATE);
truncate_inode_pages_range(inode->i_mapping, offset, offset + len - 1);
@@ -344,7 +335,7 @@ 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_FILTER_SHARED | KVM_FILTER_PRIVATE);
__kvm_gmem_invalidate_end(f, 0, -1ul);
list_del(&f->entry);
@@ -525,7 +516,8 @@ 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);
+ kvm_gmem_invalidate_start(mapping->host, start, end,
+ KVM_FILTER_SHARED | KVM_FILTER_PRIVATE);
/*
* Do not truncate the range, what action is taken in response to the
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 10/41] KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (8 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 09/41] KVM: guest_memfd: Filter both shared and private when invalidating Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 11/41] KVM: guest_memfd: Ensure pages are not in use before conversion Ackerley Tng via B4 Relay
` (30 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Add a new ioctl (and matching struct), KVM_SET_MEMORY_ATTRIBUTES2, using
the same base ioctl number (0xd2), but with R/W semantics for the kernel
instead of just read semantics. "Officially" documenting that KVM writes
to the payload will allow KVM to support partial/incremental conversions,
instead of all-or-nothing updates (which requires complex unwinding), by
recording the failing offset if an error occurs.
Opportunistically add a new struct as well, even though KVM could squeeze
the error offset into "struct kvm_memory_attributes", as there's no cost to
doing so in practice. Pad the struct with a pile of extra space to try and
avoid ending up with "struct kvm_memory_attributes3" in the future. Use
the same layout for the fields 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 62afc031897ce..1a3f664dbb197 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.
@@ -6382,6 +6382,8 @@ 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
-------------------------------
@@ -6575,6 +6577,65 @@ 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 419011097fa8e..80985e28e3b21 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -997,6 +997,7 @@ struct kvm_enable_cap {
#define KVM_CAP_S390_KEYOP 247
#define KVM_CAP_S390_VSIE_ESAMODE 248
#define KVM_CAP_S390_HPAGE_2G 249
+#define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 250
struct kvm_irq_routing_irqchip {
__u32 irqchip;
@@ -1649,6 +1650,20 @@ 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 b1537226e5adf..3783e63476569 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -492,11 +492,130 @@ bool kvm_gmem_is_private(struct kvm *kvm, gfn_t gfn)
}
EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_is_private);
+/*
+ * 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 0a5a1bee8de0f..c4c09593ef8b9 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;
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 11/41] KVM: guest_memfd: Ensure pages are not in use before conversion
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (9 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 10/41] KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2 Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-08 0:29 ` Yan Zhao
2026-08-07 21:52 ` [PATCH v10 12/41] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion Ackerley Tng via B4 Relay
` (29 subsequent siblings)
40 siblings, 1 reply; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
When converting memory to private in guest_memfd, it is necessary to ensure
that the pages are not currently being accessed by any other part of the
kernel or userspace to avoid any current user writing to guest private
memory.
guest_memfd checks for unexpected refcounts to determine whether a page is
still in use. The only expected refcounts 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 to userspace. 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 | 66 ++++++++++++++++++++++++++++++++++++++----
3 files changed, 80 insertions(+), 8 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 1a3f664dbb197..1e64026d7c1e9 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6583,7 +6583,7 @@ 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:
@@ -6592,6 +6592,8 @@ 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
========== ===============================================================
@@ -6605,6 +6607,7 @@ Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
::
struct kvm_memory_attributes2 {
+ /* in */
union {
__u64 address;
__u64 offset;
@@ -6612,7 +6615,9 @@ 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)
@@ -6634,6 +6639,16 @@ 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 80985e28e3b21..129d6f6303251 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1661,7 +1661,8 @@ 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 3783e63476569..13c3989136f67 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -524,8 +524,42 @@ 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_is_safe_for_conversion(struct inode *inode, pgoff_t start,
+ size_t nr_pages, pgoff_t *err_index)
+{
+ struct address_space *mapping = inode->i_mapping;
+ const int filemap_get_folios_refcount = 1;
+ pgoff_t last = start + nr_pages - 1;
+ struct folio_batch fbatch;
+ bool safe = true;
+ pgoff_t next;
+ int i;
+
+ folio_batch_init(&fbatch);
+
+ next = start;
+ while (safe && filemap_get_folios(mapping, &next, last, &fbatch)) {
+ for (i = 0; i < folio_batch_count(&fbatch); ++i) {
+ struct folio *folio = fbatch.folios[i];
+
+ if (folio_ref_count(folio) !=
+ folio_nr_pages(folio) + filemap_get_folios_refcount) {
+ safe = false;
+ *err_index = max(start, folio->index);
+ break;
+ }
+ }
+
+ folio_batch_release(&fbatch);
+ cond_resched();
+ }
+
+ return safe;
+}
+
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;
@@ -542,8 +576,21 @@ 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) {
+ unmap_mapping_pages(mapping, start, nr_pages, false);
+
+ if (!kvm_gmem_is_safe_for_conversion(inode, start, nr_pages,
+ err_index)) {
+ mas_destroy(&mas);
+ r = -EAGAIN;
+ goto out;
+ }
+ }
/*
* From this point on guest_memfd has performed necessary
@@ -564,9 +611,10 @@ 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;
@@ -592,8 +640,16 @@ 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,
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* Re: [PATCH v10 11/41] KVM: guest_memfd: Ensure pages are not in use before conversion
2026-08-07 21:52 ` [PATCH v10 11/41] KVM: guest_memfd: Ensure pages are not in use before conversion Ackerley Tng via B4 Relay
@ 2026-08-08 0:29 ` Yan Zhao
0 siblings, 0 replies; 43+ messages in thread
From: Yan Zhao @ 2026-08-08 0:29 UTC (permalink / raw)
To: ackerleytng
Cc: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, forkloop, pratyush, suzuki.poulose, aneesh.kumar, liam,
Paolo Bonzini, Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Andrew Morton, Chris Li,
Kairui Song, Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen,
Yuanchu Xie, Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt,
Kiryl Shutsemau, Baoquan He, Jason Gunthorpe, John Hubbard,
Peter Xu, tarunsahu, Vlastimil Babka, kvm, linux-kernel,
linux-trace-kernel, linux-doc, linux-kselftest, linux-mm,
linux-coco
On Fri, Aug 07, 2026 at 02:52:50PM -0700, Ackerley Tng via B4 Relay wrote:
> From: Ackerley Tng <ackerleytng@google.com>
>
> When converting memory to private in guest_memfd, it is necessary to ensure
> that the pages are not currently being accessed by any other part of the
> kernel or userspace to avoid any current user writing to guest private
> memory.
>
> guest_memfd checks for unexpected refcounts to determine whether a page is
> still in use. The only expected refcounts 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 to userspace. 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 | 66 ++++++++++++++++++++++++++++++++++++++----
> 3 files changed, 80 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 1a3f664dbb197..1e64026d7c1e9 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6583,7 +6583,7 @@ 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:
> @@ -6592,6 +6592,8 @@ 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
> ========== ===============================================================
>
> @@ -6605,6 +6607,7 @@ Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
> ::
>
> struct kvm_memory_attributes2 {
> + /* in */
> union {
> __u64 address;
> __u64 offset;
> @@ -6612,7 +6615,9 @@ 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)
> @@ -6634,6 +6639,16 @@ 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 80985e28e3b21..129d6f6303251 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1661,7 +1661,8 @@ 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 3783e63476569..13c3989136f67 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -524,8 +524,42 @@ 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_is_safe_for_conversion(struct inode *inode, pgoff_t start,
> + size_t nr_pages, pgoff_t *err_index)
> +{
> + struct address_space *mapping = inode->i_mapping;
> + const int filemap_get_folios_refcount = 1;
> + pgoff_t last = start + nr_pages - 1;
> + struct folio_batch fbatch;
> + bool safe = true;
> + pgoff_t next;
> + int i;
> +
> + folio_batch_init(&fbatch);
> +
> + next = start;
> + while (safe && filemap_get_folios(mapping, &next, last, &fbatch)) {
> + for (i = 0; i < folio_batch_count(&fbatch); ++i) {
> + struct folio *folio = fbatch.folios[i];
> +
> + if (folio_ref_count(folio) !=
> + folio_nr_pages(folio) + filemap_get_folios_refcount) {
> + safe = false;
> + *err_index = max(start, folio->index);
> + break;
> + }
> + }
> +
> + folio_batch_release(&fbatch);
> + cond_resched();
> + }
> +
> + return safe;
> +}
> +
> 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;
> @@ -542,8 +576,21 @@ 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) {
> + unmap_mapping_pages(mapping, start, nr_pages, false);
> +
> + if (!kvm_gmem_is_safe_for_conversion(inode, start, nr_pages,
> + err_index)) {
Note: conversion failures could occur if another vCPU is attempting to map a GFN
within this range.
CPU 0 (setting attributes) CPU 1 (attempting to map)
-------------------------- --------------------
A: mmu_invalidate_retry_gfn_unsafe
filemap_invalidate_lock_shared
__kvm_gmem_get_pfn ==> folio refcount++
filemap_invalidate_unlock_shared
filemap_invalidate_lock
filemap_get_folios
check folio_ref_count(folio) ==> Not match !!
filemap_invalidate_unlock
B: read_lock(&vcpu->kvm->mmu_lock);
is_page_fault_stale
kvm_mmu_finish_page_fault ==>folio recount--
read_unlock(&vcpu->kvm->mmu_lock);
Retrying in kvm_gmem_is_safe_for_conversion() or moving the invocation of
kvm_mmu_invalidate_start() + kvm_mmu_invalidate_range_add() to an earlier
position does not help as long as CPU 1 stays at stage A.
So, should we avoid this failure?
e.g., by moving filemap_invalidate_unlock_shared() from stage A to after
stage B?
> + mas_destroy(&mas);
> + r = -EAGAIN;
> + goto out;
> + }
> + }
>
> /*
> * From this point on guest_memfd has performed necessary
> @@ -564,9 +611,10 @@ 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;
> @@ -592,8 +640,16 @@ 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,
>
> --
> 2.55.0.654.g21b8a5bc05-goog
>
>
^ permalink raw reply [flat|nested] 43+ messages in thread
* [PATCH v10 12/41] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (10 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 11/41] KVM: guest_memfd: Ensure pages are not in use before conversion Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 13/41] KVM: guest_memfd: Return early if range already has requested attributes Ackerley Tng via B4 Relay
` (28 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Fuad Tabba
From: Ackerley Tng <ackerleytng@google.com>
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.
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 the be faulted, or
whether it is a conversion.
This 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 14d86851fce78..497da6aaf2942 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 f1d977060489b..39968610868fd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10647,6 +10647,11 @@ 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 dfdb3c97a7ac9..a341c434a2b7e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2613,6 +2613,7 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm,
#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);
+void kvm_arch_gmem_make_shared(kvm_pfn_t pfn, kvm_pfn_t nr_pages);
#endif
#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 13c3989136f67..c9874bd85c5d8 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -557,6 +557,43 @@ static bool kvm_gmem_is_safe_for_conversion(struct inode *inode, pgoff_t start,
return safe;
}
+#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)
@@ -599,7 +636,12 @@ 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_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);
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 13/41] KVM: guest_memfd: Return early if range already has requested attributes
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (11 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 12/41] KVM: guest_memfd: Call arch make_shared callback for to-shared conversion Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 14/41] mm/gup: factor out LRU cache draining for folio into lru_cache_drain_for_folio() Ackerley Tng via B4 Relay
` (27 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Provide function to check that a range has given attributes.
Optimize setting memory attributes by returning early if all pages in the
requested range already has the requested attributes.
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.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 c9874bd85c5d8..896699afcad9d 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -95,6 +95,24 @@ 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.
@@ -605,12 +623,15 @@ 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) {
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 14/41] mm/gup: factor out LRU cache draining for folio into lru_cache_drain_for_folio()
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (12 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 13/41] KVM: guest_memfd: Return early if range already has requested attributes Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 15/41] KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check Ackerley Tng via B4 Relay
` (26 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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 | 15 ++-------------
mm/swap.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 58 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 bde05664fe9a9..1bd8915517196 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;
@@ -2293,18 +2293,7 @@ static unsigned long collect_longterm_unpinnable_folios(
* but also to remove any other folio references from LRU
* caches.
*/
- if (drained == 0 && folio_may_be_lru_cached(folio) &&
- folio_ref_count(folio) !=
- folio_expected_ref_count(folio) + pin_refs) {
- lru_add_drain();
- drained = 1;
- }
- if (drained == 1 && folio_may_be_lru_cached(folio) &&
- folio_ref_count(folio) !=
- folio_expected_ref_count(folio) + pin_refs) {
- lru_add_drain_all();
- drained = 2;
- }
+ lru_cache_drain_for_folio(folio, pin_refs, &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);
/*
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 15/41] KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (13 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 14/41] mm/gup: factor out LRU cache draining for folio into lru_cache_drain_for_folio() Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 16/41] KVM: guest_memfd: Zero page while getting pfn Ackerley Tng via B4 Relay
` (25 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Vlastimil Babka (SUSE)
From: Ackerley Tng <ackerleytng@google.com>
A guest_memfd folio is safe for conversion if guest_memfd holds the last
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 extra refcounts 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.
This one known "usage" of the folio is handled by draining the lru_add
fbatch. After draining, if the refcount is still elevated, then there's
truly some other user of this page, and the page is not safe for
conversion.
If the page may be dma pinned, DMA is obviously using it and hence not safe
for conversions. If the page is still mapped after guest_memfd tried to
unmap it earlier in the conversion process, it is also obviously not safe
for conversion. 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>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
mm/swap.c | 2 ++
virt/kvm/guest_memfd.c | 23 +++++++++++++++++++----
2 files changed, 21 insertions(+), 4 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 896699afcad9d..030af0855f8b0 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"
@@ -542,11 +543,26 @@ 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_safe_for_conversion(struct folio *folio,
+ enum lru_cache_drained *drained)
+{
+ const int filemap_get_folios_refcount = 1;
+
+ if (folio_maybe_dma_pinned(folio) || folio_mapped(folio))
+ return false;
+
+ lru_cache_drain_for_folio(folio, filemap_get_folios_refcount,
+ drained);
+
+ return folio_ref_count(folio) ==
+ folio_nr_pages(folio) + filemap_get_folios_refcount;
+}
+
static bool kvm_gmem_is_safe_for_conversion(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;
- const int filemap_get_folios_refcount = 1;
pgoff_t last = start + nr_pages - 1;
struct folio_batch fbatch;
bool safe = true;
@@ -560,9 +576,8 @@ static bool kvm_gmem_is_safe_for_conversion(struct inode *inode, pgoff_t start,
for (i = 0; i < folio_batch_count(&fbatch); ++i) {
struct folio *folio = fbatch.folios[i];
- if (folio_ref_count(folio) !=
- folio_nr_pages(folio) + filemap_get_folios_refcount) {
- safe = false;
+ safe = __folio_safe_for_conversion(folio, &drained);
+ if (!safe) {
*err_index = max(start, folio->index);
break;
}
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 16/41] KVM: guest_memfd: Zero page while getting pfn
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (14 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 15/41] KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 17/41] KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE Ackerley Tng via B4 Relay
` (24 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
From: Ackerley Tng <ackerleytng@google.com>
Move the folio initialization logic from kvm_gmem_get_pfn() into
__kvm_gmem_get_pfn() to also zero pages if the page is to be used in
kvm_gmem_populate().
With in-place conversion, the existing data in a guest_memfd page can be
populated into guest memory through platform-specific ioctls.
Without first zeroing the page obtained using __kvm_gmem_get_pfn(), it
might contain uninitialized host memory, which would leak to the guest if
the populate completes.
guest_memfd pages are zeroed at most once in the page's entire lifetime
with guest_memfd, and that is tracked using the uptodate flag.
Zeroing the page in __kvm_gmem_get_pfn() is chosen over zeroing in
kvm_gmem_get_folio() since other flows, such as a future write() syscall,
can get a page, write to the page and then set page uptodate without
zeroing.
This aligns with the concept of zeroing before first use - the other place
where zeroing happens is in kvm_gmem_fault_user_mapping().
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>
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 030af0855f8b0..41950c8105b5d 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -1079,6 +1079,11 @@ 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;
@@ -1108,11 +1113,6 @@ 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);
- }
-
#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT
if (kvm_gmem_is_private_mem(file_inode(file), index))
r = kvm_arch_gmem_make_private(kvm, gfn, *pfn,
@@ -1159,8 +1159,6 @@ 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);
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 17/41] KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
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2026-08-07 21:52 ` [PATCH v10 16/41] KVM: guest_memfd: Zero page while getting pfn Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 18/41] KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION Ackerley Tng via B4 Relay
` (23 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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 fcb41dfde4c02..f708fccf71307 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2395,7 +2395,7 @@ 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);
@@ -2428,8 +2428,8 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
if (copy_from_user(¶ms, 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 &&
@@ -2441,7 +2441,8 @@ 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);
@@ -2488,7 +2489,7 @@ 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), ¶ms, sizeof(params)))
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c4c09593ef8b9..c8faf1cb82167 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
/*
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 18/41] KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (16 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 17/41] KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 19/41] KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86 Ackerley Tng via B4 Relay
` (22 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Update tdx_gmem_post_populate() to handle cases where userspace requests
"no source page". To handle "no source page", populate (perform
TDH.MEM.PAGE.ADD) using memory in-place at the target PFN.
Allow "no source page" only when gmem_in_place_conversion is enabled,
because retroactively adding support for out-of-place conversion would mean
requiring a userspace update for a feature that's being deprecated.
Also, KVM supporting "no source page" without in-place conversion would
effectively be an obscure zero-page optimization that relies on the page
being zeroed when it is allocated by guest_memfd.
Rejecting "no source page" without in-place conversion scenario is valuable
for KVM developers since it helps newcomers understand what exactly is and
isn't possible.
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/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(®ion, 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--;
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 19/41] KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (17 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 18/41] KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:52 ` [PATCH v10 20/41] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes Ackerley Tng via B4 Relay
` (21 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
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>
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
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 20/41] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (18 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 19/41] KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86 Ackerley Tng via B4 Relay
@ 2026-08-07 21:52 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 21/41] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs Ackerley Tng via B4 Relay
` (20 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:52 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
From: Ackerley Tng <ackerleytng@google.com>
Make gmem_in_place_conversion a module parameter so that userspace can
configure enable or disable the use of VM-level memory attributes. The
module parameter is only available if CONFIG_KVM_VM_MEMORY_ATTRIBUTES is
enabled.
To avoid inconsistencies in the way memory attributes are tracked in KVM
and guest_memfd, the vm_memory_attributes module_param is made
read-only (0444).
Since selecting CONFIG_KVM_VM_MEMORY_ATTRIBUTES disables in-place
conversion, actually make CONFIG_KVM_VM_MEMORY_ATTRIBUTES selectable. Make
the config only selectable for (CoCo) VM types that might use
vm_memory_attributes.
Since memory attributes are trackable in guest_memfd, the concept of having
private memory is no longer dependent on
CONFIG_KVM_VM_MEMORY_ATTRIBUTES. Define kvm_arch_has_private_mem() based on
platform config, so that having private memory is dependent on (CoCo) VM
type.
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>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
arch/x86/include/asm/kvm_host.h | 4 +++-
arch/x86/kvm/Kconfig | 14 ++++++++++----
virt/kvm/kvm_main.c | 5 ++++-
3 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 497da6aaf2942..bb2c1ade62cf9 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
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 c8faf1cb82167..85dfc3f5af805 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
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 21/41] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (19 preceding siblings ...)
2026-08-07 21:52 ` [PATCH v10 20/41] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 22/41] KVM: selftests: Create gmem fd before "regular" fd when adding memslot Ackerley Tng via B4 Relay
` (19 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng, Xiaoyao Li
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>
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 39968610868fd..1ac60628b4c07 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10631,14 +10631,15 @@ 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
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 22/41] KVM: selftests: Create gmem fd before "regular" fd when adding memslot
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (20 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 21/41] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 23/41] KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset} Ackerley Tng via B4 Relay
` (18 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Sean Christopherson <seanjc@google.com>
When adding a memslot associated 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();
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 23/41] KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset}
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (21 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 22/41] KVM: selftests: Create gmem fd before "regular" fd when adding memslot Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 24/41] KVM: selftests: Add support for mmap() on guest_memfd in core library Ackerley Tng via B4 Relay
` (17 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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;
}
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 24/41] KVM: selftests: Add support for mmap() on guest_memfd in core library
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (22 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 23/41] KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset} Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 25/41] KVM: selftests: Add selftests global for guest memory attributes capability Ackerley Tng via B4 Relay
` (16 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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;
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 25/41] KVM: selftests: Add selftests global for guest memory attributes capability
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (23 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 24/41] KVM: selftests: Add support for mmap() on guest_memfd in core library Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 26/41] KVM: selftests: Add helpers for calling ioctls on guest_memfd Ackerley Tng via B4 Relay
` (15 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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();
}
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 26/41] KVM: selftests: Add helpers for calling ioctls on guest_memfd
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (24 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 25/41] KVM: selftests: Add selftests global for guest memory attributes capability Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 27/41] KVM: selftests: Test basic single-page conversion flow Ackerley Tng via B4 Relay
` (14 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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);
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 27/41] KVM: selftests: Test basic single-page conversion flow
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (25 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 26/41] KVM: selftests: Add helpers for calling ioctls on guest_memfd Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 28/41] KVM: selftests: Test conversion flow when INIT_SHARED Ackerley Tng via B4 Relay
` (13 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Add a selftest for the guest_memfd memory attribute conversion ioctls.
The test starts the guest_memfd as all-private (the default state), and
verifies the basic flow of converting a single page to shared and then back
to private.
Add infrastructure that supports extensions to other conversion flow
tests. This infrastructure will be used in upcoming patches for other
conversion tests.
Add test as an x86-specific test since guest_memfd's testing
vehicle (KVM_X86_SW_PROTECTED_VM) is x86-specific.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
v10: Updated __GMEM_CONVERSION_TEST macro to avoid potential macro argument
reuse
---
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../kvm/x86/guest_memfd_conversions_test.c | 200 +++++++++++++++++++++
2 files changed, 201 insertions(+)
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 00123169a190a..049306cf0bb7a 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);
+}
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 28/41] KVM: selftests: Test conversion flow when INIT_SHARED
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (26 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 27/41] KVM: selftests: Test basic single-page conversion flow Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 29/41] KVM: selftests: Test conversion precision in guest_memfd Ackerley Tng via B4 Relay
` (12 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Add a test case to verify that conversions between private and shared
memory work correctly when the memory is initially created as shared.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
.../selftests/kvm/x86/guest_memfd_conversions_test.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index 77f95d49349ce..4c20d3d8e9349 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -97,6 +97,12 @@ static void __gmem_conversions_##test(test_data_t *t, int nr_pages) \
#define GMEM_CONVERSION_TEST_INIT_PRIVATE(test) \
__GMEM_CONVERSION_TEST_INIT_PRIVATE(test, 1)
+#define __GMEM_CONVERSION_TEST_INIT_SHARED(test, __nr_pages) \
+ GMEM_CONVERSION_TEST(test, __nr_pages, GUEST_MEMFD_FLAG_INIT_SHARED)
+
+#define GMEM_CONVERSION_TEST_INIT_SHARED(test) \
+ __GMEM_CONVERSION_TEST_INIT_SHARED(test, 1)
+
struct guest_check_data {
void *mem;
char expected_val;
@@ -188,6 +194,13 @@ GMEM_CONVERSION_TEST_INIT_PRIVATE(init_private)
test_convert_to_private(t, 0, 'C', 'E');
}
+GMEM_CONVERSION_TEST_INIT_SHARED(init_shared)
+{
+ test_shared(t, 0, 0, 'A', 'B');
+ test_convert_to_private(t, 0, 'B', 'C');
+ test_convert_to_shared(t, 0, 'C', 'D', 'E');
+}
+
int main(int argc, char *argv[])
{
TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 29/41] KVM: selftests: Test conversion precision in guest_memfd
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (27 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 28/41] KVM: selftests: Test conversion flow when INIT_SHARED Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 30/41] KVM: selftests: Test conversion before allocation Ackerley Tng via B4 Relay
` (11 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
The existing guest_memfd conversion tests only use single-page memory
regions. This provides no coverage for multi-page guest_memfd objects,
specifically whether KVM correctly handles the page index for conversion
operations. An incorrect implementation could, for example, always operate
on the first page regardless of the index provided.
Add a new test case to verify that conversions between private and shared
memory correctly target the specified page within a multi-page guest_memfd.
This test also verifies the precision of memory conversions by converting a
single page an then iterating through all other pages 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));
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 30/41] KVM: selftests: Test conversion before allocation
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (28 preceding siblings ...)
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@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 31/41] KVM: selftests: Convert with allocated folios in different layouts Ackerley Tng via B4 Relay
` (10 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Add two test cases to the guest_memfd conversions selftest to cover
the scenario where a conversion is requested before any memory has been
allocated in the guest_memfd region.
The KVM_SET_MEMORY_ATTRIBUTES2 ioctl can be called on a memory region at
any time. If the guest had not yet faulted in any pages for that region,
the kernel must record the conversion request and apply the requested state
when the pages are eventually allocated.
The new tests cover both conversion directions.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
.../selftests/kvm/x86/guest_memfd_conversions_test.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index a8d89df53e46d..f46f1530a94b9 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -268,6 +268,20 @@ GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(indexing, 4)
#undef combine
}
+/*
+ * Test that even if there are no folios yet, conversion requests are recorded
+ * in guest_memfd.
+ */
+GMEM_CONVERSION_TEST_INIT_SHARED(before_allocation_shared)
+{
+ test_convert_to_private(t, 0, 0, 'A');
+}
+
+GMEM_CONVERSION_TEST_INIT_PRIVATE(before_allocation_private)
+{
+ test_convert_to_shared(t, 0, 0, 'A', 'B');
+}
+
int main(int argc, char *argv[])
{
TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 31/41] KVM: selftests: Convert with allocated folios in different layouts
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (29 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 30/41] KVM: selftests: Test conversion before allocation Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 32/41] KVM: selftests: Test that truncation does not change shared/private status Ackerley Tng via B4 Relay
` (9 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Add a guest_memfd selftest to verify that memory conversions work
correctly with allocated folios in different layouts.
By iterating through which pages are initially faulted, the test covers
various layouts of contiguous allocated and unallocated regions, exercising
conversion with different range layouts.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
.../kvm/x86/guest_memfd_conversions_test.c | 30 ++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index f46f1530a94b9..acdff2d154046 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -282,6 +282,36 @@ GMEM_CONVERSION_TEST_INIT_PRIVATE(before_allocation_private)
test_convert_to_shared(t, 0, 0, 'A', 'B');
}
+/*
+ * Test that when some of the folios in the conversion range are allocated,
+ * conversion requests are handled correctly in guest_memfd. Vary the ranges
+ * allocated before conversion, using test_page, to cover various layouts of
+ * contiguous allocated and unallocated regions.
+ */
+GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(unallocated_folios, 8)
+{
+ const int second_page_to_fault = 4;
+ int i;
+
+ /*
+ * Fault 2 of the pages to test filemap range operations except when
+ * test_page == second_page_to_fault.
+ */
+ host_do_rmw(t->mem, test_page, 0, 'A');
+ if (test_page != second_page_to_fault)
+ host_do_rmw(t->mem, second_page_to_fault, 0, 'A');
+
+ gmem_set_private(t->gmem_fd, 0, nr_pages * page_size);
+ for (i = 0; i < nr_pages; ++i) {
+ char expected = (i == test_page || i == second_page_to_fault) ? 'A' : 0;
+
+ test_private(t, i, expected, 'B');
+ }
+
+ for (i = 0; i < nr_pages; ++i)
+ test_convert_to_shared(t, i, 'B', 'C', 'D');
+}
+
int main(int argc, char *argv[])
{
TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 32/41] KVM: selftests: Test that truncation does not change shared/private status
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (30 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 31/41] KVM: selftests: Convert with allocated folios in different layouts Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 33/41] KVM: selftests: Test that shared/private status is consistent across processes Ackerley Tng via B4 Relay
` (8 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Add a test to verify that deallocating a page in a guest memfd region via
fallocate() with FALLOC_FL_PUNCH_HOLE does not alter the shared or private
status of the corresponding memory range.
When a page backing a guest memfd mapping is deallocated, e.g., by punching
a hole or truncating the file, and then subsequently faulted back in, the
new page must inherit the correct shared/private status tracked by
guest_memfd.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
.../selftests/kvm/x86/guest_memfd_conversions_test.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index acdff2d154046..b7a54d2a90928 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -10,6 +10,7 @@
#include <linux/sizes.h>
#include "kvm_util.h"
+#include "kvm_syscalls.h"
#include "kselftest_harness.h"
#include "test_util.h"
#include "ucall_common.h"
@@ -312,6 +313,19 @@ GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(unallocated_folios, 8)
test_convert_to_shared(t, i, 'B', 'C', 'D');
}
+/* Truncation should not affect shared/private status. */
+GMEM_CONVERSION_TEST_INIT_SHARED(truncate)
+{
+ host_do_rmw(t->mem, 0, 0, 'A');
+ kvm_fallocate(t->gmem_fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+ host_do_rmw(t->mem, 0, 0, 'A');
+
+ test_convert_to_private(t, 0, 'A', 'B');
+
+ kvm_fallocate(t->gmem_fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+ test_private(t, 0, 0, 'A');
+}
+
int main(int argc, char *argv[])
{
TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 33/41] KVM: selftests: Test that shared/private status is consistent across processes
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (31 preceding siblings ...)
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@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 34/41] KVM: selftests: Add helpers to pin pages with CONFIG_GUP_TEST Ackerley Tng via B4 Relay
` (7 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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));
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 34/41] KVM: selftests: Add helpers to pin pages with CONFIG_GUP_TEST
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (32 preceding siblings ...)
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@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 35/41] KVM: selftests: Test conversion with elevated page refcount Ackerley Tng via B4 Relay
` (6 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Add helper functions to allow KVM selftests to pin memory using
CONFIG_GUP_TEST. This is useful for testing scenarios where some page has
an increased refcount. such as in guest_memfd in-place conversion tests.
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);
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 35/41] KVM: selftests: Test conversion with elevated page refcount
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (33 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 34/41] KVM: selftests: Add helpers to pin pages with CONFIG_GUP_TEST Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 36/41] KVM: selftests: Reset shared memory after hole-punching Ackerley Tng via B4 Relay
` (5 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Add a selftest to verify that converting a shared guest_memfd page to a
private page fails if the page has an elevated reference count.
When KVM converts a shared page to a private one, it expects the page to
have a reference count equal to the reference counts taken by the
filemap. If another kernel subsystem holds a reference to the page, the
conversion must be aborted.
The test asserts that both bulk and single-page conversion attempts
correctly fail with EAGAIN for the pinned page. After the page is unpinned,
the test verifies that subsequent conversions succeed.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
.../kvm/x86/guest_memfd_conversions_test.c | 56 ++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
index a972a09c5c6e5..e1c84df0f0596 100644
--- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c
@@ -444,6 +444,62 @@ GMEM_CONVERSION_TEST_INIT_SHARED(forked_accesses)
#undef TEST_STATE_AWAIT
}
+static void test_convert_to_private_fails(test_data_t *t, u64 pgoff,
+ size_t nr_pages,
+ u64 expected_error_offset)
+{
+ /* +1 to make it anything but expected_error_offset. */
+ u64 error_offset = expected_error_offset + 1;
+ u64 offset = pgoff * page_size;
+ int ret;
+
+ do {
+ ret = __gmem_set_private(t->gmem_fd, offset,
+ nr_pages * page_size, &error_offset);
+ } while (ret == -1 && errno == EINTR);
+ TEST_ASSERT(ret == -1 && errno == EAGAIN,
+ "Wanted EAGAIN on page %lu, got %d (ret = %d)", pgoff,
+ errno, ret);
+ TEST_ASSERT_EQ(error_offset, expected_error_offset);
+}
+
+GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(elevated_refcount, 4)
+{
+ int i;
+
+ pin_pages(t->mem + test_page * page_size, page_size);
+
+ for (i = 0; i < nr_pages; i++)
+ test_shared(t, i, 0, 'A', 'B');
+
+ /*
+ * Converting in bulk should fail as long any page in the range has
+ * unexpected refcounts.
+ */
+ test_convert_to_private_fails(t, 0, nr_pages, test_page * page_size);
+
+ for (i = 0; i < nr_pages; i++) {
+ /*
+ * Converting page-wise should also fail as long any page in the
+ * range has unexpected refcounts.
+ */
+ if (i == test_page)
+ test_convert_to_private_fails(t, i, 1, test_page * page_size);
+ else
+ test_convert_to_private(t, i, 'B', 'C');
+ }
+
+ unpin_pages();
+
+ gmem_set_private(t->gmem_fd, 0, nr_pages * page_size);
+
+ for (i = 0; i < nr_pages; i++) {
+ char expected = i == test_page ? 'B' : 'C';
+
+ test_private(t, i, expected, 'D');
+ }
+}
+
int main(int argc, char *argv[])
{
TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 36/41] KVM: selftests: Reset shared memory after hole-punching
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (34 preceding siblings ...)
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@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
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` (4 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
private_mem_conversions_test used to reset the shared memory that was used
for the test to an initial pattern at the end of each test iteration. Then,
it would punch out the pages, which would zero memory.
Without in-place conversion, the resetting would write shared memory, and
hole-punching will zero private memory, hence resetting the test to the
state at the beginning of the for loop.
With in-place conversion, resetting writes memory as shared, and
hole-punching zeroes the same physical memory, hence undoing the reset
done before the hole punch.
Move the resetting after the hole-punching, and reset the entire
PER_CPU_DATA_SIZE instead of just the tested range.
With in-place conversion, this zeroes and then resets the same physical
memory. Without in-place conversion, the private memory is zeroed, and the
shared memory is reset to init_p.
This is sufficient since at each test stage, the memory is assumed to start
as shared, and private memory is always assumed to start zeroed. Conversion
zeroes memory, so the future test stages will work as expected.
Fixes: 43f623f350ce1 ("KVM: selftests: Add x86-only selftest for private memory conversions")
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
tools/testing/selftests/kvm/x86/private_mem_conversions_test.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
index f3de2a4ab0551..cf50e9a332c5b 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -202,15 +202,18 @@ static void guest_test_explicit_conversion(u64 base_gpa, bool do_fallocate)
guest_sync_shared(gpa, size, p3, p4);
memcmp_g(gpa, p4, size);
- /* Reset the shared memory back to the initial pattern. */
- memset((void *)gpa, init_p, size);
-
/*
* Free (via PUNCH_HOLE) *all* private memory so that the next
* iteration starts from a clean slate, e.g. with respect to
* whether or not there are pages/folios in guest_mem.
*/
guest_map_shared(base_gpa, PER_CPU_DATA_SIZE, true);
+
+ /*
+ * Hole-punching above zeroed private memory. Reset shared
+ * memory in preparation for the next GUEST_STAGE.
+ */
+ memset((void *)base_gpa, init_p, PER_CPU_DATA_SIZE);
}
}
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 37/41] KVM: selftests: Provide function to look up guest_memfd details from gpa
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (35 preceding siblings ...)
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@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 38/41] KVM: selftests: Provide common function to set memory attributes Ackerley Tng via B4 Relay
` (3 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Introduce a new helper, kvm_gpa_to_guest_memfd(), to find the
guest_memfd-related details of a memory region that contains a given guest
physical address (GPA).
The function returns the file descriptor for the memfd, the offset into
the file that corresponds to the GPA, and the number of bytes remaining
in the region from that GPA.
kvm_gpa_to_guest_memfd() was factored out from vm_guest_mem_fallocate();
refactor vm_guest_mem_fallocate() to use the new helper.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
tools/testing/selftests/kvm/include/kvm_util.h | 3 +++
tools/testing/selftests/kvm/lib/kvm_util.c | 37 ++++++++++++++++----------
2 files changed, 26 insertions(+), 14 deletions(-)
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 3cfe243d7c8b0..795c9eb311071 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -428,6 +428,9 @@ static inline void vm_enable_cap(struct kvm_vm *vm, u32 cap, u64 arg0)
vm_ioctl(vm, KVM_ENABLE_CAP, &enable_cap);
}
+int kvm_gpa_to_guest_memfd(struct kvm_vm *vm, gpa_t gpa, off_t *fd_offset,
+ size_t *nr_bytes);
+
/*
* KVM_SET_MEMORY_ATTRIBUTES{,2} overwrites _all_ attributes. These
* flows need significant enhancements to support multiple attributes.
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index b1456ed76e27e..1188d0a6c0a5f 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1332,27 +1332,20 @@ void vm_guest_mem_fallocate(struct kvm_vm *vm, u64 base, u64 size,
bool punch_hole)
{
const int mode = FALLOC_FL_KEEP_SIZE | (punch_hole ? FALLOC_FL_PUNCH_HOLE : 0);
- struct userspace_mem_region *region;
u64 end = base + size;
- gpa_t gpa, len;
off_t fd_offset;
- int ret;
+ int fd, ret;
+ size_t len;
+ gpa_t gpa;
for (gpa = base; gpa < end; gpa += len) {
- u64 offset;
-
- region = userspace_mem_region_find(vm, gpa, gpa);
- TEST_ASSERT(region && region->region.flags & KVM_MEM_GUEST_MEMFD,
- "Private memory region not found for GPA 0x%lx", gpa);
+ fd = kvm_gpa_to_guest_memfd(vm, gpa, &fd_offset, &len);
+ len = min(end - gpa, len);
- offset = gpa - region->region.guest_phys_addr;
- fd_offset = region->region.guest_memfd_offset + offset;
- len = min_t(u64, end - gpa, region->region.memory_size - offset);
-
- ret = fallocate(region->region.guest_memfd, mode, fd_offset, len);
+ ret = fallocate(fd, mode, fd_offset, len);
TEST_ASSERT(!ret, "fallocate() failed to %s at %lx (len = %lu), fd = %d, mode = %x, offset = %lx",
punch_hole ? "punch hole" : "allocate", gpa, len,
- region->region.guest_memfd, mode, fd_offset);
+ fd, mode, fd_offset);
}
}
@@ -1689,6 +1682,22 @@ void *addr_gpa2alias(struct kvm_vm *vm, gpa_t gpa)
return (void *) ((uintptr_t) region->host_alias + offset);
}
+int kvm_gpa_to_guest_memfd(struct kvm_vm *vm, gpa_t gpa, off_t *fd_offset,
+ size_t *nr_bytes)
+{
+ struct userspace_mem_region *region;
+ gpa_t gpa_offset;
+
+ region = userspace_mem_region_find(vm, gpa, gpa);
+ TEST_ASSERT(region && region->region.flags & KVM_MEM_GUEST_MEMFD,
+ "guest_memfd memory region not found for GPA 0x%lx", gpa);
+
+ gpa_offset = gpa - region->region.guest_phys_addr;
+ *fd_offset = region->region.guest_memfd_offset + gpa_offset;
+ *nr_bytes = region->region.memory_size - gpa_offset;
+ return region->region.guest_memfd;
+}
+
/* Create an interrupt controller chip for the specified VM. */
void vm_create_irqchip(struct kvm_vm *vm)
{
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 38/41] KVM: selftests: Provide common function to set memory attributes
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (36 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 37/41] KVM: selftests: Provide function to look up guest_memfd details from gpa Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 39/41] KVM: selftests: Make TEST_EXPECT_SIGBUS thread-safe Ackerley Tng via B4 Relay
` (2 subsequent siblings)
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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);
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 39/41] KVM: selftests: Make TEST_EXPECT_SIGBUS thread-safe
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (37 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 38/41] KVM: selftests: Provide common function to set memory attributes Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 40/41] KVM: selftests: Update private_mem_conversions_test to mmap() guest_memfd Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 41/41] KVM: selftests: Update private memory exits test to work with per-gmem attributes Ackerley Tng via B4 Relay
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
The TEST_EXPECT_SIGBUS macro is not thread-safe as it uses a global
sigjmp_buf and installs a global SIGBUS signal handler. If multiple threads
execute the macro concurrently, they will race on installing the signal
handler and stomp on other threads' jump buffers, leading to incorrect test
behavior.
Make TEST_EXPECT_SIGBUS thread-safe with the following changes:
Share the KVM tests' global signal handler. sigaction() applies to all
threads; without sharing a global signal handler, one thread may have
removed the signal handler that another thread added, hence leading to
unexpected signals.
The alternative of layering signal handlers was considered, but calling
sigaction() within TEST_EXPECT_SIGBUS() necessarily creates a race. To
avoid adding new setup and teardown routines to do sigaction() and keep
usage of TEST_EXPECT_SIGBUS() simple, share the KVM tests' global signal
handler.
Opportunistically rename report_unexpected_signal to
catchall_signal_handler.
To continue to only expect SIGBUS within specific regions of code, use a
thread-specific variable, expecting_sigbus, to replace installing and
removing signal handlers.
Make the execution environment for the thread, sigjmp_buf, a
thread-specific variable.
As part of TEST_EXPECT_SIGBUS(), assert the prerequisite for this setup,
that the current signal handler is the catchall_signal_handler.
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
tools/testing/selftests/kvm/include/test_util.h | 32 +++++++++++++------------
tools/testing/selftests/kvm/lib/kvm_util.c | 18 ++++++++++----
tools/testing/selftests/kvm/lib/test_util.c | 7 ------
3 files changed, 30 insertions(+), 27 deletions(-)
diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index d5825211f2727..75e98ec14107f 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -83,21 +83,23 @@ do { \
__builtin_unreachable(); \
} while (0)
-extern sigjmp_buf expect_sigbus_jmpbuf;
-void expect_sigbus_handler(int signum);
-
-#define TEST_EXPECT_SIGBUS(action) \
-do { \
- struct sigaction sa_old, sa_new = { \
- .sa_handler = expect_sigbus_handler, \
- }; \
- \
- sigaction(SIGBUS, &sa_new, &sa_old); \
- if (sigsetjmp(expect_sigbus_jmpbuf, 1) == 0) { \
- action; \
- TEST_FAIL("'%s' should have triggered SIGBUS", #action); \
- } \
- sigaction(SIGBUS, &sa_old, NULL); \
+extern __thread sigjmp_buf expect_sigbus_jmpbuf;
+extern __thread volatile sig_atomic_t expecting_sigbus;
+void catchall_signal_handler(int signum);
+
+#define TEST_EXPECT_SIGBUS(action) \
+do { \
+ struct sigaction __sa = {}; \
+ \
+ TEST_ASSERT_EQ(sigaction(SIGBUS, NULL, &__sa), 0); \
+ TEST_ASSERT_EQ(__sa.sa_handler, &catchall_signal_handler); \
+ \
+ expecting_sigbus = true; \
+ if (sigsetjmp(expect_sigbus_jmpbuf, 1) == 0) { \
+ action; \
+ TEST_FAIL("'%s' should have triggered SIGBUS", #action);\
+ } \
+ expecting_sigbus = false; \
} while (0)
size_t parse_size(const char *size);
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 1188d0a6c0a5f..cac5624e99774 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -2316,13 +2316,20 @@ __weak void kvm_selftest_arch_init(void)
{
}
-static void report_unexpected_signal(int signum)
+__thread sigjmp_buf expect_sigbus_jmpbuf;
+__thread volatile sig_atomic_t expecting_sigbus;
+
+void catchall_signal_handler(int signum)
{
+ switch (signum) {
+ case SIGBUS: {
+ if (expecting_sigbus)
+ siglongjmp(expect_sigbus_jmpbuf, 1);
+
+ TEST_FAIL("Unexpected SIGBUS (%d)\n", signum);
+ }
#define KVM_CASE_SIGNUM(sig) \
case sig: TEST_FAIL("Unexpected " #sig " (%d)\n", signum)
-
- switch (signum) {
- KVM_CASE_SIGNUM(SIGBUS);
KVM_CASE_SIGNUM(SIGSEGV);
KVM_CASE_SIGNUM(SIGILL);
KVM_CASE_SIGNUM(SIGFPE);
@@ -2334,12 +2341,13 @@ static void report_unexpected_signal(int signum)
void __attribute((constructor)) kvm_selftest_init(void)
{
struct sigaction sig_sa = {
- .sa_handler = report_unexpected_signal,
+ .sa_handler = catchall_signal_handler,
};
/* Tell stdout not to buffer its content. */
setbuf(stdout, NULL);
+ expecting_sigbus = false;
sigaction(SIGBUS, &sig_sa, NULL);
sigaction(SIGSEGV, &sig_sa, NULL);
sigaction(SIGILL, &sig_sa, NULL);
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 4dff72f6bd346..89d6d1b572959 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -19,13 +19,6 @@
#include "test_util.h"
#include "kvm_syscalls.h"
-sigjmp_buf expect_sigbus_jmpbuf;
-
-void __attribute__((used)) expect_sigbus_handler(int signum)
-{
- siglongjmp(expect_sigbus_jmpbuf, 1);
-}
-
/*
* Random number generator that is usable from guest code. This is the
* Park-Miller LCG using standard constants.
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 40/41] KVM: selftests: Update private_mem_conversions_test to mmap() guest_memfd
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (38 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 39/41] KVM: selftests: Make TEST_EXPECT_SIGBUS thread-safe Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
2026-08-07 21:53 ` [PATCH v10 41/41] KVM: selftests: Update private memory exits test to work with per-gmem attributes Ackerley Tng via B4 Relay
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, Ackerley Tng
From: Ackerley Tng <ackerleytng@google.com>
Update the private memory conversions selftest to also test conversions
that are done "in-place" via per-guest_memfd memory attributes. In-place
conversions require the host to be able to mmap() the guest_memfd so that
the host and guest can share the same backing physical memory.
This includes several updates, that are conditioned on the system
supporting per-guest_memfd attributes (kvm_has_gmem_attributes):
1. Set up guest_memfd requesting MMAP and INIT_SHARED.
2. With in-place conversions, the host's mapping points directly to the
guest's memory. When the guest converts a region to private, host access
to that region is blocked. Update the test to expect a SIGBUS when
attempting to access the host virtual address (HVA) of private memory.
3. Use vm_mem_set_memory_attributes(), which chooses how to set memory
attributes based on whether kvm_has_gmem_attributes.
Restrict the test to using VM_MEM_SRC_SHMEM because guest_memfd's required
mmap() flags and page sizes happens to align with those of
VM_MEM_SRC_SHMEM. As long as VM_MEM_SRC_SHMEM is used for src_type,
vm_mem_add() works as intended.
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/private_mem_conversions_test.c | 44 ++++++++++++++++++----
1 file changed, 36 insertions(+), 8 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..2af8d41963816 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -306,9 +306,12 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
if (do_fallocate)
vm_guest_mem_fallocate(vm, gpa, size, map_shared);
- if (set_attributes)
- vm_set_memory_attributes(vm, gpa, size,
- map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE);
+ if (set_attributes) {
+ u64 attrs = map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
+
+ vm_mem_set_memory_attributes(vm, gpa, size, attrs);
+ }
+
run->hypercall.ret = 0;
}
@@ -352,8 +355,20 @@ 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 per-guest_memfd memory attributes,
+ * i.e. in-place conversion, host accesses will
+ * point at guest memory and should SIGBUS when
+ * guest memory is private. When using per-VM
+ * attributes, i.e. separate backing for shared
+ * vs. private, the host should always observe
+ * the shared data.
+ */
+ if (kvm_has_gmem_attributes &&
+ uc.args[0] == SYNC_PRIVATE)
+ TEST_EXPECT_SIGBUS(READ_ONCE(*hva));
+ else
+ memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
/* For shared, write the new pattern to guest memory. */
if (uc.args[0] == SYNC_SHARED)
@@ -382,6 +397,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_v
const size_t slot_size = memfd_size / nr_memslots;
struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
pthread_t threads[KVM_MAX_VCPUS];
+ u64 gmem_flags;
struct kvm_vm *vm;
int memfd, i;
@@ -397,12 +413,17 @@ 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);
+ if (kvm_has_gmem_attributes)
+ gmem_flags = GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_INIT_SHARED;
+ else
+ gmem_flags = 0;
+
+ 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;
@@ -452,17 +473,24 @@ static void usage(const char *cmd)
int main(int argc, char *argv[])
{
- enum vm_mem_backing_src_type src_type = DEFAULT_VM_MEM_SRC;
+ enum vm_mem_backing_src_type src_type;
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));
+ src_type = kvm_has_gmem_attributes ? VM_MEM_SRC_SHMEM :
+ DEFAULT_VM_MEM_SRC;
+
while ((opt = getopt(argc, argv, "hm:s:n:")) != -1) {
switch (opt) {
case 's':
src_type = parse_backing_src_type(optarg);
+ TEST_ASSERT(!kvm_has_gmem_attributes ||
+ src_type == VM_MEM_SRC_SHMEM,
+ "Testing in-place conversions, only %s mem_type supported\n",
+ vm_mem_backing_src_alias(VM_MEM_SRC_SHMEM)->name);
break;
case 'n':
nr_vcpus = atoi_positive("nr_vcpus", optarg);
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread* [PATCH v10 41/41] KVM: selftests: Update private memory exits test to work with per-gmem attributes
2026-08-07 21:52 [PATCH v10 00/41] guest_memfd: In-place conversion support Ackerley Tng via B4 Relay
` (39 preceding siblings ...)
2026-08-07 21:53 ` [PATCH v10 40/41] KVM: selftests: Update private_mem_conversions_test to mmap() guest_memfd Ackerley Tng via B4 Relay
@ 2026-08-07 21:53 ` Ackerley Tng via B4 Relay
40 siblings, 0 replies; 43+ messages in thread
From: Ackerley Tng via B4 Relay @ 2026-08-07 21:53 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
jmattson, jthoughton, michael.roth, oupton, pankaj.gupta, qperret,
rick.p.edgecombe, rientjes, shivankg, steven.price, tabba, willy,
wyihan, yan.y.zhao, forkloop, pratyush, suzuki.poulose,
aneesh.kumar, liam, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Jonathan Corbet, Shuah Khan, Shuah Khan,
Vishal Annapurve, Andrew Morton, Chris Li, Kairui Song,
Kemeng Shi, Nhat Pham, Barry Song, Axel Rasmussen, Yuanchu Xie,
Wei Xu, Youngjun Park, Qi Zheng, Shakeel Butt, Kiryl Shutsemau,
Baoquan He, Jason Gunthorpe, John Hubbard, Peter Xu, tarunsahu,
Jason Gunthorpe, Vlastimil Babka, Baoquan He
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
linux-mm, linux-coco, 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);
--
2.55.0.654.g21b8a5bc05-goog
^ permalink raw reply related [flat|nested] 43+ messages in thread