linux-kernel - [PATCH 04/54] KVM: x86/mmu: Use MMU's role to detect CR4.SMEP value in nested NPT walk

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Date:   Tue, 22 Jun 2021 10:56:49 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 04/54] KVM: x86/mmu: Use MMU's role to detect CR4.SMEP value
 in nested NPT walk

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@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/paging_tmpl.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 823a5919f9fa..52fffd68b522 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -471,8 +471,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
 
 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;
-- 
2.32.0.288.g62a8d224e6-goog