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[5.12,073/700] KVM: x86/mmu: Use MMUs role to detect CR4.SMEP value in nested NPT walk

Message ID 20210712060935.020357020@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman July 12, 2021, 6:02 a.m. UTC 
From: Sean Christopherson <seanjc@google.com>

commit ef318b9edf66a082f23d00d79b70c17b4c055a26 upstream.

Use the MMU's role to get its effective SMEP value when injecting a fault
into the guest.  When walking L1's (nested) NPT while L2 is active, vCPU
state will reflect L2, whereas NPT uses the host's (L1 in this case) CR0,
CR4, EFER, etc...  If L1 and L2 have different settings for SMEP and
L1 does not have EFER.NX=1, this can result in an incorrect PFEC.FETCH
when injecting #NPF.

Fixes: e57d4a356ad3 ("KVM: Add instruction fetch checking when walking guest page table")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kvm/mmu/paging_tmpl.h |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
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Patch

--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -471,8 +471,7 @@  retry_walk:
 
 error:
 	errcode |= write_fault | user_fault;
-	if (fetch_fault && (mmu->nx ||
-			    kvm_read_cr4_bits(vcpu, X86_CR4_SMEP)))
+	if (fetch_fault && (mmu->nx || mmu->mmu_role.ext.cr4_smep))
 		errcode |= PFERR_FETCH_MASK;
 
 	walker->fault.vector = PF_VECTOR;