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KVM: MMU: load PDPTRs outside mmu_lock

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On SVM, reading PDPTRs might access guest memory, which might fault
and thus might sleep.  On the other hand, it is not possible to
release the lock after make_mmu_pages_available has been called.

Therefore, push the call to make_mmu_pages_available and the
mmu_lock critical section within mmu_alloc_direct_roots and
mmu_alloc_shadow_roots.

Reported-by: Wanpeng Li <wanpengli@tencent.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2021-04-08 08:10:25 -04:00
parent d9bd0082e2
commit 4a38162ee9
1 changed files with 37 additions and 15 deletions
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52
arch/x86/kvm/mmu/mmu.c
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@ -3245,6 +3245,12 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
u8 shadow_root_level = mmu->shadow_root_level;
hpa_t root;
unsigned i;
int r;
write_lock(&vcpu->kvm->mmu_lock);
r = make_mmu_pages_available(vcpu);
if (r < 0)
goto out_unlock;
if (is_tdp_mmu_enabled(vcpu->kvm)) {
root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu);
@ -3253,8 +3259,10 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level, true);
mmu->root_hpa = root;
} else if (shadow_root_level == PT32E_ROOT_LEVEL) {
if (WARN_ON_ONCE(!mmu->pae_root))
return -EIO;
if (WARN_ON_ONCE(!mmu->pae_root)) {
r = -EIO;
goto out_unlock;
}
for (i = 0; i < 4; ++i) {
WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i]));
@ -3267,13 +3275,15 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
mmu->root_hpa = __pa(mmu->pae_root);
} else {
WARN_ONCE(1, "Bad TDP root level = %d\n", shadow_root_level);
return -EIO;
r = -EIO;
goto out_unlock;
}
/* root_pgd is ignored for direct MMUs. */
mmu->root_pgd = 0;
return 0;
out_unlock:
write_unlock(&vcpu->kvm->mmu_lock);
return r;
}
static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
@ -3282,7 +3292,8 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
u64 pdptrs[4], pm_mask;
gfn_t root_gfn, root_pgd;
hpa_t root;
int i;
unsigned i;
int r;
root_pgd = mmu->get_guest_pgd(vcpu);
root_gfn = root_pgd >> PAGE_SHIFT;
@ -3290,6 +3301,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
if (mmu_check_root(vcpu, root_gfn))
return 1;
/*
* On SVM, reading PDPTRs might access guest memory, which might fault
* and thus might sleep. Grab the PDPTRs before acquiring mmu_lock.
*/
if (mmu->root_level == PT32E_ROOT_LEVEL) {
for (i = 0; i < 4; ++i) {
pdptrs[i] = mmu->get_pdptr(vcpu, i);
@ -3301,6 +3316,11 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
}
}
write_lock(&vcpu->kvm->mmu_lock);
r = make_mmu_pages_available(vcpu);
if (r < 0)
goto out_unlock;
/*
* Do we shadow a long mode page table? If so we need to
* write-protect the guests page table root.
@ -3312,8 +3332,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
goto set_root_pgd;
}
if (WARN_ON_ONCE(!mmu->pae_root))
return -EIO;
if (WARN_ON_ONCE(!mmu->pae_root)) {
r = -EIO;
goto out_unlock;
}
/*
* We shadow a 32 bit page table. This may be a legacy 2-level
@ -3324,8 +3346,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
if (mmu->shadow_root_level == PT64_ROOT_4LEVEL) {
pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;
if (WARN_ON_ONCE(!mmu->lm_root))
return -EIO;
if (WARN_ON_ONCE(!mmu->lm_root)) {
r = -EIO;
goto out_unlock;
}
mmu->lm_root[0] = __pa(mmu->pae_root) | pm_mask;
}
@ -3353,6 +3377,8 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
set_root_pgd:
mmu->root_pgd = root_pgd;
out_unlock:
write_unlock(&vcpu->kvm->mmu_lock);
return 0;
}
@ -4853,14 +4879,10 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
r = mmu_alloc_special_roots(vcpu);
if (r)
goto out;
write_lock(&vcpu->kvm->mmu_lock);
if (make_mmu_pages_available(vcpu))
r = -ENOSPC;
else if (vcpu->arch.mmu->direct_map)
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);
if (r)
goto out;