KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch()

The mmu_check_root() check in fast_pgd_switch() seems to be
superfluous: when GPA is outside of the visible range
cached_root_available() will fail for non-direct roots
(as we can't have a matching one on the list) and we don't
seem to care for direct ones.

Also, raising #TF immediately when a non-existent GFN is written to CR3
doesn't seem to mach architectural behavior. Drop the check.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200710141157.1640173-10-vkuznets@redhat.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 61c35fe..613c331 100644 (file)
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4243,8 +4243,7 @@ static bool fast_pgd_switch(struct kvm_vcpu *vcpu, gpa_t new_pgd,
         */
        if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL &&
            mmu->root_level >= PT64_ROOT_4LEVEL)
-               return !mmu_check_root(vcpu, new_pgd >> PAGE_SHIFT) &&
-                      cached_root_available(vcpu, new_pgd, new_role);
+               return cached_root_available(vcpu, new_pgd, new_role);
 
        return false;
 }