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

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>

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c4e0b97..9d617b9 100644 (file)
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -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;
        }