[v4,9/9] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch()
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Message ID 20200710141157.1640173-10-vkuznets@redhat.com
State New
Headers show
Series
  • KVM: nSVM: fixes for CR3/MMU switch upon nested guest entry/exit
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Commit Message

Vitaly Kuznetsov July 10, 2020, 2:11 p.m. UTC
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>
---
 arch/x86/kvm/mmu/mmu.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Patch
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diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 13ec3c30eda2..50a923696bf1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4277,8 +4277,7 @@  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;
 }