linux-kernel - [PATCH] KVM: x86: svm: report MSR_IA32_MCG_EXT

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Date:   Wed, 19 Dec 2018 12:06:13 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Joerg Roedel <joro@...tes.org>, x86@...nel.org
Subject: [PATCH] KVM: x86: svm: report MSR_IA32_MCG_EXT_CTL as unsupported

AMD doesn't seem to implement MSR_IA32_MCG_EXT_CTL and svm code in kvm
knows nothing about it, however, this MSR is among emulated_msrs and
thus returned with KVM_GET_MSR_INDEX_LIST. The consequent KVM_GET_MSRS,
of course, fails.

Report the MSR as unsupported to not confuse userspace.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/svm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 2acb42b74a51..dfdf7d0b7f88 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5845,6 +5845,13 @@ static bool svm_cpu_has_accelerated_tpr(void)
 
 static bool svm_has_emulated_msr(int index)
 {
+	switch (index) {
+	case MSR_IA32_MCG_EXT_CTL:
+		return false;
+	default:
+		break;
+	}
+
 	return true;
 }
 
-- 
2.19.2