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

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commit ef318b9edf 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: e57d4a356a ("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>
This commit is contained in:
Sean Christopherson 2021-06-22 10:56:49 -07:00 • committed by Greg Kroah-Hartman
commit 9aae145dc5
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;