linux-kernel - [PATCH 1/2] KVM: SVM: Update EFER software model on CR0 trap for SEV-ES

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Message-Id: <20210507165947.2502412-2-seanjc@google.com>
Date:   Fri,  7 May 2021 09:59:46 -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, Peter Gonda <pgonda@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 1/2] KVM: SVM: Update EFER software model on CR0 trap for SEV-ES

For protected guests, a.k.a. SEV-ES guests, update KVM's model of EFER
when processing the side effect of the CPU entering long mode when paging
is enabled.  The whole point of intercepting CR0/CR4/EFER is to keep
KVM's software model up-to-date.

Fixes: f1c6366e3043 ("KVM: SVM: Add required changes to support intercepts under SEV-ES")
Reported-by: Peter Gonda <pgonda@...gle.com>
Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index a7271f31df47..d271fe8e58de 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1696,15 +1696,17 @@ void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	u64 hcr0 = cr0;
 
 #ifdef CONFIG_X86_64
-	if (vcpu->arch.efer & EFER_LME && !vcpu->arch.guest_state_protected) {
+	if (vcpu->arch.efer & EFER_LME) {
 		if (!is_paging(vcpu) && (cr0 & X86_CR0_PG)) {
 			vcpu->arch.efer |= EFER_LMA;
-			svm->vmcb->save.efer |= EFER_LMA | EFER_LME;
+			if (!vcpu->arch.guest_state_protected)
+				svm->vmcb->save.efer |= EFER_LMA | EFER_LME;
 		}
 
 		if (is_paging(vcpu) && !(cr0 & X86_CR0_PG)) {
 			vcpu->arch.efer &= ~EFER_LMA;
-			svm->vmcb->save.efer &= ~(EFER_LMA | EFER_LME);
+			if (!vcpu->arch.guest_state_protected)
+				svm->vmcb->save.efer &= ~(EFER_LMA | EFER_LME);
 		}
 	}
 #endif
-- 
2.31.1.607.g51e8a6a459-goog