[PATCH v3 07/10] KVM: nVMX: Replace evmcs kvm_host_map with pfncache

Fred Griffoul
2025-11-21T11:11:35Z

Replace the eVMCS kvm_host_map with a gfn_to_pfn_cache to properly
handle memslot changes and unify with other pfncaches in nVMX.

The change introduces proper locking/unlocking semantics for eVMCS
access through nested_lock_evmcs() and nested_unlock_evmcs() helpers.

Signed-off-by: Fred Griffoul <fgriffo@amazon.co.uk>
---
arch/x86/kvm/vmx/hyperv.h | 21 +++----
arch/x86/kvm/vmx/nested.c | 115 ++++++++++++++++++++++++++------------
arch/x86/kvm/vmx/vmx.h | 3 +-
3 files changed, 90 insertions(+), 49 deletions(-)

diff --git a/arch/x86/kvm/vmx/hyperv.h b/arch/x86/kvm/vmx/hyperv.h
index 3c7fea501ca5..3b6fcf8dff64 100644
--- a/arch/x86/kvm/vmx/hyperv.h
+++ b/arch/x86/kvm/vmx/hyperv.h
@@ -37,11 +37,6 @@ static inline bool nested_vmx_is_evmptr12_set(struct vcpu_vmx *vmx)
return evmptr_is_set(vmx->nested.hv_evmcs_vmptr);
}

-static inline struct hv_enlightened_vmcs *nested_vmx_evmcs(struct vcpu_vmx *vmx)
-{
- return vmx->nested.hv_evmcs;
-}
-
static inline bool guest_cpu_cap_has_evmcs(struct kvm_vcpu *vcpu)
{
/*
@@ -70,6 +65,8 @@ void nested_evmcs_filter_control_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *
int nested_evmcs_check_controls(struct vmcs12 *vmcs12);
bool nested_evmcs_l2_tlb_flush_enabled(struct kvm_vcpu *vcpu);
void vmx_hv_inject_synthetic_vmexit_post_tlb_flush(struct kvm_vcpu *vcpu);
+struct hv_enlightened_vmcs *nested_lock_evmcs(struct vcpu_vmx *vmx);
+void nested_unlock_evmcs(struct vcpu_vmx *vmx);
#else
static inline bool evmptr_is_valid(u64 evmptr)
{
@@ -91,11 +88,6 @@ static inline bool nested_vmx_is_evmptr12_set(struct vcpu_vmx *vmx)
return false;
}

-static inline struct hv_enlightened_vmcs *nested_vmx_evmcs(struct vcpu_vmx *vmx)
-{
- return NULL;
-}
-
static inline u32 nested_evmcs_clean_fields(struct vcpu_vmx *vmx)
{
return 0;
@@ -105,6 +97,15 @@ static inline bool nested_evmcs_msr_bitmap(struct vcpu_vmx *vmx)
{
return false;
}
+
+static inline struct hv_enlightened_vmcs *nested_lock_evmcs(struct vcpu_vmx *vmx)
+{
+ return NULL;
+}
+
+static inline void nested_unlock_evmcs(struct vcpu_vmx *vmx)
+{
+}
#endif

#endif /* __KVM_X86_VMX_HYPERV_H */
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index aec150612818..207780ef0926 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -232,8 +232,6 @@ static inline void nested_release_evmcs(struct kvm_vcpu *vcpu)
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
struct vcpu_vmx *vmx = to_vmx(vcpu);

- kvm_vcpu_unmap(vcpu, &vmx->nested.hv_evmcs_map);
- vmx->nested.hv_evmcs = NULL;
vmx->nested.hv_evmcs_vmptr = EVMPTR_INVALID;
vmx->nested.hv_clean_fields = 0;
vmx->nested.hv_msr_bitmap = false;
@@ -265,7 +263,7 @@ static bool nested_evmcs_handle_vmclear(struct kvm_vcpu *vcpu, gpa_t vmptr)
!evmptr_is_valid(nested_get_evmptr(vcpu)))
return false;

- if (nested_vmx_evmcs(vmx) && vmptr == vmx->nested.hv_evmcs_vmptr)
+ if (vmptr == vmx->nested.hv_evmcs_vmptr)
nested_release_evmcs(vcpu);

return true;
@@ -393,6 +391,9 @@ static void free_nested(struct kvm_vcpu *vcpu)
kvm_gpc_deactivate(&vmx->nested.virtual_apic_cache);
kvm_gpc_deactivate(&vmx->nested.apic_access_page_cache);
kvm_gpc_deactivate(&vmx->nested.msr_bitmap_cache);
+#ifdef CONFIG_KVM_HYPERV
+ kvm_gpc_deactivate(&vmx->nested.hv_evmcs_cache);
+#endif

free_vpid(vmx->nested.vpid02);
vmx->nested.posted_intr_nv = -1;
@@ -1735,11 +1736,12 @@ static void copy_vmcs12_to_shadow(struct vcpu_vmx *vmx)
vmcs_load(vmx->loaded_vmcs->vmcs);
}

-static void copy_enlightened_to_vmcs12(struct vcpu_vmx *vmx, u32 hv_clean_fields)
-{
#ifdef CONFIG_KVM_HYPERV
+static void copy_enlightened_to_vmcs12(struct vcpu_vmx *vmx,
+ struct hv_enlightened_vmcs *evmcs,
+ u32 hv_clean_fields)
+{
struct vmcs12 *vmcs12 = vmx->nested.cached_vmcs12;
- struct hv_enlightened_vmcs *evmcs = nested_vmx_evmcs(vmx);
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(&vmx->vcpu);

/* HV_VMX_ENLIGHTENED_CLEAN_FIELD_NONE */
@@ -1978,16 +1980,14 @@ static void copy_enlightened_to_vmcs12(struct vcpu_vmx *vmx, u32 hv_clean_fields
*/

return;
-#else /* CONFIG_KVM_HYPERV */
- KVM_BUG_ON(1, vmx->vcpu.kvm);
-#endif /* CONFIG_KVM_HYPERV */
}
+#endif /* CONFIG_KVM_HYPERV */

static void copy_vmcs12_to_enlightened(struct vcpu_vmx *vmx)
{
#ifdef CONFIG_KVM_HYPERV
struct vmcs12 *vmcs12 = vmx->nested.cached_vmcs12;
- struct hv_enlightened_vmcs *evmcs = nested_vmx_evmcs(vmx);
+ struct hv_enlightened_vmcs *evmcs = nested_lock_evmcs(vmx);

/*
* Should not be changed by KVM:
@@ -2155,6 +2155,7 @@ static void copy_vmcs12_to_enlightened(struct vcpu_vmx *vmx)

evmcs->guest_bndcfgs = vmcs12->guest_bndcfgs;

+ nested_unlock_evmcs(vmx);
return;
#else /* CONFIG_KVM_HYPERV */
KVM_BUG_ON(1, vmx->vcpu.kvm);
@@ -2171,6 +2172,8 @@ static enum nested_evmptrld_status nested_vmx_handle_enlightened_vmptrld(
#ifdef CONFIG_KVM_HYPERV
struct vcpu_vmx *vmx = to_vmx(vcpu);
struct hv_enlightened_vmcs *evmcs;
+ struct gfn_to_pfn_cache *gpc;
+ enum nested_evmptrld_status status = EVMPTRLD_SUCCEEDED;
bool evmcs_gpa_changed = false;
u64 evmcs_gpa;

@@ -2183,17 +2186,19 @@ static enum nested_evmptrld_status nested_vmx_handle_enlightened_vmptrld(
return EVMPTRLD_DISABLED;
}

+ gpc = &vmx->nested.hv_evmcs_cache;
+ if (nested_gpc_lock(gpc, evmcs_gpa)) {
+ nested_release_evmcs(vcpu);
+ return EVMPTRLD_ERROR;
+ }
+
+ evmcs = gpc->khva;
+
if (unlikely(evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) {
vmx->nested.current_vmptr = INVALID_GPA;

nested_release_evmcs(vcpu);

- if (kvm_vcpu_map(vcpu, gpa_to_gfn(evmcs_gpa),
- &vmx->nested.hv_evmcs_map))
- return EVMPTRLD_ERROR;
-
- vmx->nested.hv_evmcs = vmx->nested.hv_evmcs_map.hva;
-
/*
* Currently, KVM only supports eVMCS version 1
* (== KVM_EVMCS_VERSION) and thus we expect guest to set this
@@ -2216,10 +2221,11 @@ static enum nested_evmptrld_status nested_vmx_handle_enlightened_vmptrld(
* eVMCS version or VMCS12 revision_id as valid values for first
* u32 field of eVMCS.
*/
- if ((vmx->nested.hv_evmcs->revision_id != KVM_EVMCS_VERSION) &&
- (vmx->nested.hv_evmcs->revision_id != VMCS12_REVISION)) {
+ if ((evmcs->revision_id != KVM_EVMCS_VERSION) &&
+ (evmcs->revision_id != VMCS12_REVISION)) {
nested_release_evmcs(vcpu);
- return EVMPTRLD_VMFAIL;
+ status = EVMPTRLD_VMFAIL;
+ goto unlock;
}

vmx->nested.hv_evmcs_vmptr = evmcs_gpa;
@@ -2244,14 +2250,11 @@ static enum nested_evmptrld_status nested_vmx_handle_enlightened_vmptrld(
* between different L2 guests as KVM keeps a single VMCS12 per L1.
*/
if (from_launch || evmcs_gpa_changed) {
- vmx->nested.hv_evmcs->hv_clean_fields &=
- ~HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;
-
+ evmcs->hv_clean_fields &= ~HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;
vmx->nested.force_msr_bitmap_recalc = true;
}

/* Cache evmcs fields to avoid reading evmcs after copy to vmcs12 */
- evmcs = vmx->nested.hv_evmcs;
vmx->nested.hv_clean_fields = evmcs->hv_clean_fields;
vmx->nested.hv_flush_hypercall = evmcs->hv_enlightenments_control.nested_flush_hypercall;
vmx->nested.hv_msr_bitmap = evmcs->hv_enlightenments_control.msr_bitmap;
@@ -2260,13 +2263,15 @@ static enum nested_evmptrld_status nested_vmx_handle_enlightened_vmptrld(
struct vmcs12 *vmcs12 = get_vmcs12(vcpu);

if (likely(!vmcs12->hdr.shadow_vmcs)) {
- copy_enlightened_to_vmcs12(vmx, vmx->nested.hv_clean_fields);
+ copy_enlightened_to_vmcs12(vmx, evmcs, vmx->nested.hv_clean_fields);
/* Enlightened VMCS doesn't have launch state */
vmcs12->launch_state = !from_launch;
}
}

- return EVMPTRLD_SUCCEEDED;
+unlock:
+ nested_gpc_unlock(gpc);
+ return status;
#else
return EVMPTRLD_DISABLED;
#endif
@@ -2771,7 +2776,6 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
enum vm_entry_failure_code *entry_failure_code)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- struct hv_enlightened_vmcs *evmcs;
bool load_guest_pdptrs_vmcs12 = false;

if (vmx->nested.dirty_vmcs12 || nested_vmx_is_evmptr12_valid(vmx)) {
@@ -2909,9 +2913,13 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
* bits when it changes a field in eVMCS. Mark all fields as clean
* here.
*/
- evmcs = nested_vmx_evmcs(vmx);
- if (evmcs)
+ if (nested_vmx_is_evmptr12_valid(vmx)) {
+ struct hv_enlightened_vmcs *evmcs;
+
+ evmcs = nested_lock_evmcs(vmx);
evmcs->hv_clean_fields |= HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;
+ nested_unlock_evmcs(vmx);
+ }

return 0;
}
@@ -4147,6 +4155,18 @@ static void *nested_gpc_lock_if_active(struct gfn_to_pfn_cache *gpc)
return gpc->khva;
}

+#ifdef CONFIG_KVM_HYPERV
+struct hv_enlightened_vmcs *nested_lock_evmcs(struct vcpu_vmx *vmx)
+{
+ return nested_gpc_lock_if_active(&vmx->nested.hv_evmcs_cache);
+}
+
+void nested_unlock_evmcs(struct vcpu_vmx *vmx)
+{
+ nested_gpc_unlock(&vmx->nested.hv_evmcs_cache);
+}
+#endif
+
static struct pi_desc *nested_lock_pi_desc(struct vcpu_vmx *vmx)
{
u8 *pi_desc_page;
@@ -5636,6 +5656,9 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu)
kvm_gpc_init_for_vcpu(&vmx->nested.virtual_apic_cache, vcpu);
kvm_gpc_init_for_vcpu(&vmx->nested.pi_desc_cache, vcpu);

+#ifdef CONFIG_KVM_HYPERV
+ kvm_gpc_init(&vmx->nested.hv_evmcs_cache, vcpu->kvm);
+#endif
vmx->nested.vmcs02_initialized = false;
vmx->nested.vmxon = true;

@@ -5887,6 +5910,8 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
/* Read the field, zero-extended to a u64 value */
value = vmcs12_read_any(vmcs12, field, offset);
} else {
+ struct hv_enlightened_vmcs *evmcs;
+
/*
* Hyper-V TLFS (as of 6.0b) explicitly states, that while an
* enlightened VMCS is active VMREAD/VMWRITE instructions are
@@ -5905,7 +5930,9 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
return nested_vmx_fail(vcpu, VMXERR_UNSUPPORTED_VMCS_COMPONENT);

/* Read the field, zero-extended to a u64 value */
- value = evmcs_read_any(nested_vmx_evmcs(vmx), field, offset);
+ evmcs = nested_lock_evmcs(vmx);
+ value = evmcs_read_any(evmcs, field, offset);
+ nested_unlock_evmcs(vmx);
}

/*
@@ -6935,6 +6962,27 @@ bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu)
return true;
}

+static void vmx_get_enlightened_to_vmcs12(struct vcpu_vmx *vmx)
+{
+#ifdef CONFIG_KVM_HYPERV
+ struct hv_enlightened_vmcs *evmcs;
+ struct kvm_vcpu *vcpu = &vmx->vcpu;
+
+ kvm_vcpu_srcu_read_lock(vcpu);
+ evmcs = nested_lock_evmcs(vmx);
+ /*
+ * L1 hypervisor is not obliged to keep eVMCS
+ * clean fields data always up-to-date while
+ * not in guest mode, 'hv_clean_fields' is only
+ * supposed to be actual upon vmentry so we need
+ * to ignore it here and do full copy.
+ */
+ copy_enlightened_to_vmcs12(vmx, evmcs, 0);
+ nested_unlock_evmcs(vmx);
+ kvm_vcpu_srcu_read_unlock(vcpu);
+#endif /* CONFIG_KVM_HYPERV */
+}
+
static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
struct kvm_nested_state __user *user_kvm_nested_state,
u32 user_data_size)
@@ -7025,14 +7073,7 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
copy_vmcs02_to_vmcs12_rare(vcpu, get_vmcs12(vcpu));
if (!vmx->nested.need_vmcs12_to_shadow_sync) {
if (nested_vmx_is_evmptr12_valid(vmx))
- /*
- * L1 hypervisor is not obliged to keep eVMCS
- * clean fields data always up-to-date while
- * not in guest mode, 'hv_clean_fields' is only
- * supposed to be actual upon vmentry so we need
- * to ignore it here and do full copy.
- */
- copy_enlightened_to_vmcs12(vmx, 0);
+ vmx_get_enlightened_to_vmcs12(vmx);
else if (enable_shadow_vmcs)
copy_shadow_to_vmcs12(vmx);
}
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 87708af502f3..4da5a42b0c60 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -208,8 +208,7 @@ struct nested_vmx {
u32 hv_clean_fields;
bool hv_msr_bitmap;
bool hv_flush_hypercall;
- struct hv_enlightened_vmcs *hv_evmcs;
- struct kvm_host_map hv_evmcs_map;
+ struct gfn_to_pfn_cache hv_evmcs_cache;
#endif
};

--
2.43.0