linux-kernel - [PATCH] KVM: nSVM: check for EFER.SVME=1 before entering guest

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Date:   Wed, 18 Mar 2020 13:41:40 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH] KVM: nSVM: check for EFER.SVME=1 before entering guest

EFER is set for L2 using svm_set_efer, which hardcodes EFER_SVME to 1 and hides
an incorrect value for EFER.SVME in the L1 VMCB.  Perform the check manually
to detect invalid guest state.

Reported-by: Krish Sadhukhan <krish.sadhukhan@...cle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 08568ae9f7a1..2125c6ae5951 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3558,6 +3558,9 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
 
 static bool nested_vmcb_checks(struct vmcb *vmcb)
 {
+	if ((vmcb->save.efer & EFER_SVME) == 0)
+		return false;
+
 	if ((vmcb->control.intercept & (1ULL << INTERCEPT_VMRUN)) == 0)
 		return false;
 
-- 
1.8.3.1