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KVM: x86/mmu: Ignore guest CR3 on fast root switch for direct MMU

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Ignore the guest's CR3 when looking for a cached root for a direct MMU,
the guest's CR3 has no impact on the direct MMU's shadow pages (the
role check ensures compatibility with CR0.WP, etc...).

Zero out root_cr3 when allocating the direct roots to make it clear that
it's ignored.

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-02-28 14:52:39 -08:00 committed by Paolo Bonzini
parent cc7f5577ad
commit 3651c7fc2b
1 changed files with 5 additions and 3 deletions
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8
arch/x86/kvm/mmu/mmu.c
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@ -3730,7 +3730,9 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root);
} else
BUG();
vcpu->arch.mmu->root_cr3 = vcpu->arch.mmu->get_cr3(vcpu);
/* root_cr3 is ignored for direct MMUs. */
vcpu->arch.mmu->root_cr3 = 0;
return 0;
}
@ -4272,8 +4274,8 @@ static bool cached_root_available(struct kvm_vcpu *vcpu, gpa_t new_cr3,
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
swap(root, mmu->prev_roots[i]);
if (new_cr3 == root.cr3 && VALID_PAGE(root.hpa) &&
page_header(root.hpa) != NULL &&
if ((new_role.direct || new_cr3 == root.cr3) &&
VALID_PAGE(root.hpa) && page_header(root.hpa) &&
new_role.word == page_header(root.hpa)->role.word)
break;
}