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Message-Id: <20210302184540.2829328-4-seanjc@google.com>
Date: Tue, 2 Mar 2021 10:45:28 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>,
Brijesh Singh <brijesh.singh@....com>,
Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH 03/15] KVM: x86/mmu: Ensure MMU pages are available when
allocating roots
Hold the mmu_lock for write for the entire duration of allocating and
initializing an MMU's roots. This ensures there are MMU pages available
and thus prevents root allocations from failing. That in turn fixes a
bug where KVM would fail to free valid PAE roots if a one of the later
roots failed to allocate.
Note, KVM still leaks the PAE roots if the lm_root allocation fails.
This will be addressed in a future commit.
Cc: Ben Gardon <bgardon@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
arch/x86/kvm/mmu/mmu.c | 41 ++++++++++++--------------------------
arch/x86/kvm/mmu/tdp_mmu.c | 23 +++++----------------
2 files changed, 18 insertions(+), 46 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 2ed3fac1244e..1f129001a30c 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2398,6 +2398,9 @@ static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
{
unsigned long avail = kvm_mmu_available_pages(vcpu->kvm);
+ /* Ensure all four PAE roots can be allocated in a single pass. */
+ BUILD_BUG_ON(KVM_MIN_FREE_MMU_PAGES < 4);
+
if (likely(avail >= KVM_MIN_FREE_MMU_PAGES))
return 0;
@@ -3220,16 +3223,9 @@ static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
{
struct kvm_mmu_page *sp;
- write_lock(&vcpu->kvm->mmu_lock);
-
- if (make_mmu_pages_available(vcpu)) {
- write_unlock(&vcpu->kvm->mmu_lock);
- return INVALID_PAGE;
- }
sp = kvm_mmu_get_page(vcpu, gfn, gva, level, direct, ACC_ALL);
++sp->root_count;
- write_unlock(&vcpu->kvm->mmu_lock);
return __pa(sp->spt);
}
@@ -3241,16 +3237,10 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
if (is_tdp_mmu_enabled(vcpu->kvm)) {
root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu);
-
- if (!VALID_PAGE(root))
- return -ENOSPC;
vcpu->arch.mmu->root_hpa = root;
} else if (shadow_root_level >= PT64_ROOT_4LEVEL) {
root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level,
true);
-
- if (!VALID_PAGE(root))
- return -ENOSPC;
vcpu->arch.mmu->root_hpa = root;
} else if (shadow_root_level == PT32E_ROOT_LEVEL) {
for (i = 0; i < 4; ++i) {
@@ -3258,8 +3248,6 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT),
i << 30, PT32_ROOT_LEVEL, true);
- if (!VALID_PAGE(root))
- return -ENOSPC;
vcpu->arch.mmu->pae_root[i] = root | PT_PRESENT_MASK;
}
vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root);
@@ -3294,8 +3282,6 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
root = mmu_alloc_root(vcpu, root_gfn, 0,
vcpu->arch.mmu->shadow_root_level, false);
- if (!VALID_PAGE(root))
- return -ENOSPC;
vcpu->arch.mmu->root_hpa = root;
goto set_root_pgd;
}
@@ -3325,6 +3311,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
for (i = 0; i < 4; ++i) {
MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu->pae_root[i]));
+
if (vcpu->arch.mmu->root_level == PT32E_ROOT_LEVEL) {
pdptr = vcpu->arch.mmu->get_pdptr(vcpu, i);
if (!(pdptr & PT_PRESENT_MASK)) {
@@ -3338,8 +3325,6 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
root = mmu_alloc_root(vcpu, root_gfn, i << 30,
PT32_ROOT_LEVEL, false);
- if (!VALID_PAGE(root))
- return -ENOSPC;
vcpu->arch.mmu->pae_root[i] = root | pm_mask;
}
vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root);
@@ -3373,14 +3358,6 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
return 0;
}
-static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
-{
- if (vcpu->arch.mmu->direct_map)
- return mmu_alloc_direct_roots(vcpu);
- else
- return mmu_alloc_shadow_roots(vcpu);
-}
-
void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
{
int i;
@@ -4822,7 +4799,15 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
r = mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->direct_map);
if (r)
goto out;
- r = mmu_alloc_roots(vcpu);
+ write_lock(&vcpu->kvm->mmu_lock);
+ if (make_mmu_pages_available(vcpu))
+ r = -ENOSPC;
+ else if (vcpu->arch.mmu->direct_map)
+ r = mmu_alloc_direct_roots(vcpu);
+ else
+ r = mmu_alloc_shadow_roots(vcpu);
+ write_unlock(&vcpu->kvm->mmu_lock);
+
kvm_mmu_sync_roots(vcpu);
if (r)
goto out;
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 70226e0875fe..50ef757c5586 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -137,22 +137,21 @@ static struct kvm_mmu_page *alloc_tdp_mmu_page(struct kvm_vcpu *vcpu, gfn_t gfn,
return sp;
}
-static struct kvm_mmu_page *get_tdp_mmu_vcpu_root(struct kvm_vcpu *vcpu)
+hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
{
union kvm_mmu_page_role role;
struct kvm *kvm = vcpu->kvm;
struct kvm_mmu_page *root;
+ lockdep_assert_held_write(&kvm->mmu_lock);
+
role = page_role_for_level(vcpu, vcpu->arch.mmu->shadow_root_level);
- write_lock(&kvm->mmu_lock);
-
/* Check for an existing root before allocating a new one. */
for_each_tdp_mmu_root(kvm, root) {
if (root->role.word == role.word) {
kvm_mmu_get_root(kvm, root);
- write_unlock(&kvm->mmu_lock);
- return root;
+ goto out;
}
}
@@ -161,19 +160,7 @@ static struct kvm_mmu_page *get_tdp_mmu_vcpu_root(struct kvm_vcpu *vcpu)
list_add(&root->link, &kvm->arch.tdp_mmu_roots);
- write_unlock(&kvm->mmu_lock);
-
- return root;
-}
-
-hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
-{
- struct kvm_mmu_page *root;
-
- root = get_tdp_mmu_vcpu_root(vcpu);
- if (!root)
- return INVALID_PAGE;
-
+out:
return __pa(root->spt);
}
--
2.30.1.766.gb4fecdf3b7-goog
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