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KVM: x86/mmu: Use MMU's role to detect CR4.SMEP value in nested NPT walk

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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>
This commit is contained in:
Sean Christopherson 2021-06-22 10:56:49 -07:00 committed by Paolo Bonzini
parent 0aa1837533
commit ef318b9edf
1 changed files with 1 additions and 2 deletions
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3
arch/x86/kvm/mmu/paging_tmpl.h
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@ -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;