[PATCH v6 2/7] KVM: x86: Move PML page to common vcpu arch structure

Nikunj A Dadhania
2026-04-07T06:33:30Z

Move the PML page pointer from VMX-specific vcpu_vmx structure to the
common kvm_vcpu_arch structure to enable sharing between VMX and SVM
implementations. Only the page pointer is moved to x86 common code while
keeping allocation logic vendor-specific, since AMD requires
snp_safe_alloc_page() for PML buffer allocation.

Update all VMX references accordingly, and simplify the
kvm_flush_pml_buffer() interface by removing the page parameter since it
can now access the page directly from the vcpu structure.

No functional change, restructuring to prepare for SVM PML support.

Suggested-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/vmx/vmx.c | 24 ++++++++++++------------
arch/x86/kvm/vmx/vmx.h | 2 --
arch/x86/kvm/x86.c | 4 ++--
arch/x86/kvm/x86.h | 2 +-
5 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6e4e3ef9b8c7..9ed19e99d481 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -873,6 +873,8 @@ struct kvm_vcpu_arch {
*/
struct kvm_mmu_memory_cache mmu_external_spt_cache;

+ struct page *pml_page;
+
/*
* QEMU userspace and the guest each have their own FPU state.
* In vcpu_run, we switch between the user and guest FPU contexts.
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b77750a2efc2..909085a5dfb3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4934,7 +4934,8 @@ int vmx_vcpu_precreate(struct kvm *kvm)

static void init_vmcs(struct vcpu_vmx *vmx)
{
- struct kvm *kvm = vmx->vcpu.kvm;
+ struct kvm_vcpu *vcpu = &vmx->vcpu;
+ struct kvm *kvm = vcpu->kvm;
struct kvm_vmx *kvm_vmx = to_kvm_vmx(kvm);

if (nested)
@@ -5026,7 +5027,7 @@ static void init_vmcs(struct vcpu_vmx *vmx)
vmcs_write64(XSS_EXIT_BITMAP, VMX_XSS_EXIT_BITMAP);

if (enable_pml) {
- vmcs_write64(PML_ADDRESS, page_to_phys(vmx->pml_pg));
+ vmcs_write64(PML_ADDRESS, page_to_phys(vcpu->arch.pml_page));
vmcs_write16(GUEST_PML_INDEX, PML_HEAD_INDEX);
}

@@ -6491,17 +6492,16 @@ void vmx_get_entry_info(struct kvm_vcpu *vcpu, u32 *intr_info, u32 *error_code)
*error_code = 0;
}

-static void vmx_destroy_pml_buffer(struct vcpu_vmx *vmx)
+static void vmx_destroy_pml_buffer(struct kvm_vcpu *vcpu)
{
- if (vmx->pml_pg) {
- __free_page(vmx->pml_pg);
- vmx->pml_pg = NULL;
+ if (vcpu->arch.pml_page) {
+ __free_page(vcpu->arch.pml_page);
+ vcpu->arch.pml_page = NULL;
}
}

static void vmx_flush_pml_buffer(struct kvm_vcpu *vcpu)
{
- struct vcpu_vmx *vmx = to_vmx(vcpu);
u16 pml_idx;

pml_idx = vmcs_read16(GUEST_PML_INDEX);
@@ -6510,7 +6510,7 @@ static void vmx_flush_pml_buffer(struct kvm_vcpu *vcpu)
if (pml_idx == PML_HEAD_INDEX)
return;

- kvm_flush_pml_buffer(vcpu, vmx->pml_pg, pml_idx);
+ kvm_flush_pml_buffer(vcpu, pml_idx);

/* reset PML index */
vmcs_write16(GUEST_PML_INDEX, PML_HEAD_INDEX);
@@ -7738,7 +7738,7 @@ void vmx_vcpu_free(struct kvm_vcpu *vcpu)
struct vcpu_vmx *vmx = to_vmx(vcpu);

if (enable_pml)
- vmx_destroy_pml_buffer(vmx);
+ vmx_destroy_pml_buffer(vcpu);
free_vpid(vmx->vpid);
nested_vmx_free_vcpu(vcpu);
free_loaded_vmcs(vmx->loaded_vmcs);
@@ -7767,8 +7767,8 @@ int vmx_vcpu_create(struct kvm_vcpu *vcpu)
* for the guest), etc.
*/
if (enable_pml) {
- vmx->pml_pg = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
- if (!vmx->pml_pg)
+ vcpu->arch.pml_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+ if (!vcpu->arch.pml_page)
goto free_vpid;
}

@@ -7839,7 +7839,7 @@ int vmx_vcpu_create(struct kvm_vcpu *vcpu)
free_vmcs:
free_loaded_vmcs(vmx->loaded_vmcs);
free_pml:
- vmx_destroy_pml_buffer(vmx);
+ vmx_destroy_pml_buffer(vcpu);
free_vpid:
free_vpid(vmx->vpid);
return err;
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 9b0c5dde9437..ba04d32a1412 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -262,8 +262,6 @@ struct vcpu_vmx {
unsigned int ple_window;
bool ple_window_dirty;

- struct page *pml_pg;
-
/* apic deadline value in host tsc */
u64 hv_deadline_tsc;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 628b6f51d2be..52c06d095c25 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6720,7 +6720,7 @@ void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
kvm_vcpu_kick(vcpu);
}

-void kvm_flush_pml_buffer(struct kvm_vcpu *vcpu, struct page *pml_page, u16 pml_idx)
+void kvm_flush_pml_buffer(struct kvm_vcpu *vcpu, u16 pml_idx)
{
u16 pml_tail_index;
u64 *pml_buf;
@@ -6739,7 +6739,7 @@ void kvm_flush_pml_buffer(struct kvm_vcpu *vcpu, struct page *pml_page, u16 pml_
* Read the entries in the same order they were written, to ensure that
* the dirty ring is filled in the same order the CPU wrote them.
*/
- pml_buf = page_address(pml_page);
+ pml_buf = page_address(vcpu->arch.pml_page);

for (i = PML_HEAD_INDEX; i >= pml_tail_index; i--) {
u64 gpa;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 3b2cc2756033..21d88a768d8e 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -769,6 +769,6 @@ static inline bool kvm_is_valid_u_s_cet(struct kvm_vcpu *vcpu, u64 data)
/* PML is written backwards: this is the first entry written by the CPU */
#define PML_HEAD_INDEX (PML_LOG_NR_ENTRIES-1)

-void kvm_flush_pml_buffer(struct kvm_vcpu *vcpu, struct page *pml_pg, u16 pml_idx);
+void kvm_flush_pml_buffer(struct kvm_vcpu *vcpu, u16 pml_idx);

#endif
--
2.48.1