Set lpage_disallowed in TDP MMU shadow pages before making the SP visible
to other readers, i.e. before setting its SPTE. This will allow KVM to
query lpage_disallowed when determining if a shadow page can be replaced
by a NX huge page without violating the rules of the mitigation.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 14 ++++++++++----
arch/x86/kvm/mmu/mmu_internal.h | 2 +-
arch/x86/kvm/mmu/tdp_mmu.c | 20 ++++++++++++--------
3 files changed, 23 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 1361eb4599b4..5cb845fae56e 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -812,14 +812,20 @@ static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
kvm_mmu_gfn_disallow_lpage(slot, gfn);
}
-void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp)
+void __account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
- if (sp->lpage_disallowed)
- return;
-
++kvm->stat.nx_lpage_splits;
list_add_tail(&sp->lpage_disallowed_link,
&kvm->arch.lpage_disallowed_mmu_pages);
+}
+
+static void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp)
+{
+ if (sp->lpage_disallowed)
+ return;
+
+ __account_huge_nx_page(kvm, sp);
+
sp->lpage_disallowed = true;
}
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 1bff453f7cbe..4a0087efa1e3 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -168,7 +168,7 @@ void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_
void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
-void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp);
+void __account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp);
void unaccount_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp);
#endif /* __KVM_X86_MMU_INTERNAL_H */
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index b3b6426725d4..f05423545e6d 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1122,16 +1122,13 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
* @kvm: kvm instance
* @iter: a tdp_iter instance currently on the SPTE that should be set
* @sp: The new TDP page table to install.
- * @account_nx: True if this page table is being installed to split a
- * non-executable huge page.
* @shared: This operation is running under the MMU lock in read mode.
*
* Returns: 0 if the new page table was installed. Non-0 if the page table
* could not be installed (e.g. the atomic compare-exchange failed).
*/
static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
- struct kvm_mmu_page *sp, bool account_nx,
- bool shared)
+ struct kvm_mmu_page *sp, bool shared)
{
u64 spte = make_nonleaf_spte(sp->spt, !shadow_accessed_mask);
int ret = 0;
@@ -1146,8 +1143,6 @@ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
spin_lock(&kvm->arch.tdp_mmu_pages_lock);
list_add(&sp->link, &kvm->arch.tdp_mmu_pages);
- if (account_nx)
- account_huge_nx_page(kvm, sp);
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
return 0;
@@ -1160,6 +1155,7 @@ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
+ struct kvm *kvm = vcpu->kvm;
struct tdp_iter iter;
struct kvm_mmu_page *sp;
int ret;
@@ -1210,10 +1206,18 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
sp = tdp_mmu_alloc_sp(vcpu);
tdp_mmu_init_child_sp(sp, &iter);
- if (tdp_mmu_link_sp(vcpu->kvm, &iter, sp, account_nx, true)) {
+ sp->lpage_disallowed = account_nx;
+
+ if (tdp_mmu_link_sp(kvm, &iter, sp, true)) {
tdp_mmu_free_sp(sp);
break;
}
+
+ if (account_nx) {
+ spin_lock(&kvm->arch.tdp_mmu_pages_lock);
+ __account_huge_nx_page(kvm, sp);
+ spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
+ }
}
}
@@ -1501,7 +1505,7 @@ static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter,
* correctness standpoint since the translation will be the same either
* way.
*/
- ret = tdp_mmu_link_sp(kvm, iter, sp, false, shared);
+ ret = tdp_mmu_link_sp(kvm, iter, sp, shared);
if (ret)
goto out;
base-commit: 19164ad08bf668bca4f4bfbaacaa0a47c1b737a6
--
2.35.1.1021.g381101b075-goog
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