linux-kernel - [PATCH 53/54] KVM: x86/mmu: Get CR4.SMEP from MMU, not vCPU, in shadow page fault

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Message-Id: <20210622175739.3610207-54-seanjc@google.com>
Date:   Tue, 22 Jun 2021 10:57:38 -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 53/54] KVM: x86/mmu: Get CR4.SMEP from MMU, not vCPU, in
 shadow page fault

Use the current MMU instead of vCPU state to query CR4.SMEP when handling
a page fault.  In the nested NPT case, the current CR4.SMEP reflects L2,
whereas the page fault is shadowing L1's NPT, which uses L1's hCR4.
Practically speaking, this is a nop a NPT walks are always user faults,
i.e. this code will never be reached, but fix it up for consistency.

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

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 260a9c06d764..a79353fc6efd 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -903,7 +903,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,
 		 * then we should prevent the kernel from executing it
 		 * if SMEP is enabled.
 		 */
-		if (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
+		if (is_cr4_smep(vcpu->arch.mmu))
 			walker.pte_access &= ~ACC_EXEC_MASK;
 	}
 
-- 
2.32.0.288.g62a8d224e6-goog