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Message-Id: <20220723012325.1715714-4-seanjc@google.com>
Date: Sat, 23 Jul 2022 01:23:22 +0000
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
Yosry Ahmed <yosryahmed@...gle.com>,
Mingwei Zhang <mizhang@...gle.com>,
Ben Gardon <bgardon@...gle.com>
Subject: [PATCH v2 3/6] KVM: x86/mmu: Set disallowed_nx_huge_page in TDP MMU
before setting SPTE
Set nx_huge_page_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 the flag 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@...gle.com>
---
arch/x86/kvm/mmu/mmu.c | 12 +++++-------
arch/x86/kvm/mmu/mmu_internal.h | 5 ++---
arch/x86/kvm/mmu/tdp_mmu.c | 30 +++++++++++++++++-------------
3 files changed, 24 insertions(+), 23 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 493cdf1c29ff..e9252e7cd5a2 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -802,8 +802,7 @@ static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
}
-static void untrack_possible_nx_huge_page(struct kvm *kvm,
- struct kvm_mmu_page *sp)
+void untrack_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
if (list_empty(&sp->possible_nx_huge_page_link))
return;
@@ -812,15 +811,14 @@ static void untrack_possible_nx_huge_page(struct kvm *kvm,
list_del_init(&sp->possible_nx_huge_page_link);
}
-void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
+static void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
sp->nx_huge_page_disallowed = false;
untrack_possible_nx_huge_page(kvm, sp);
}
-static void track_possible_nx_huge_page(struct kvm *kvm,
- struct kvm_mmu_page *sp)
+void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
if (!list_empty(&sp->possible_nx_huge_page_link))
return;
@@ -830,8 +828,8 @@ static void track_possible_nx_huge_page(struct kvm *kvm,
&kvm->arch.possible_nx_huge_pages);
}
-void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
- bool nx_huge_page_possible)
+static void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
+ bool nx_huge_page_possible)
{
sp->nx_huge_page_disallowed = true;
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 83644a0167ab..2a887d08b722 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -336,8 +336,7 @@ 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_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
- bool nx_huge_page_possible);
-void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
+void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
+void untrack_possible_nx_huge_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 a30983947fee..626c40ec2af9 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -392,8 +392,10 @@ static void tdp_mmu_unlink_sp(struct kvm *kvm, struct kvm_mmu_page *sp,
lockdep_assert_held_write(&kvm->mmu_lock);
list_del(&sp->link);
- if (sp->nx_huge_page_disallowed)
- unaccount_nx_huge_page(kvm, sp);
+ if (sp->nx_huge_page_disallowed) {
+ sp->nx_huge_page_disallowed = false;
+ untrack_possible_nx_huge_page(kvm, sp);
+ }
if (shared)
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
@@ -1111,16 +1113,13 @@ 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, !kvm_ad_enabled());
int ret = 0;
@@ -1135,8 +1134,6 @@ 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_nx_huge_page(kvm, sp, true);
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
return 0;
@@ -1149,6 +1146,7 @@ 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;
@@ -1185,9 +1183,6 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
}
if (!is_shadow_present_pte(iter.old_spte)) {
- bool account_nx = fault->huge_page_disallowed &&
- fault->req_level >= iter.level;
-
/*
* If SPTE has been frozen by another thread, just
* give up and retry, avoiding unnecessary page table
@@ -1199,10 +1194,19 @@ 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->nx_huge_page_disallowed = fault->huge_page_disallowed;
+
+ if (tdp_mmu_link_sp(kvm, &iter, sp, true)) {
tdp_mmu_free_sp(sp);
break;
}
+
+ if (fault->huge_page_disallowed &&
+ fault->req_level >= iter.level) {
+ spin_lock(&kvm->arch.tdp_mmu_pages_lock);
+ track_possible_nx_huge_page(kvm, sp);
+ spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
+ }
}
}
@@ -1490,7 +1494,7 @@ 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;
--
2.37.1.359.gd136c6c3e2-goog
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