linux-kernel - [PATCH] x86/kvm/nVMX: read from MSR_IA32_VMX_PROCBASED

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Message-Id: <20190207104214.8142-1-vkuznets@redhat.com>
Date:   Thu,  7 Feb 2019 11:42:14 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] x86/kvm/nVMX: read from MSR_IA32_VMX_PROCBASED_CTLS2 only when it is available

SDM says MSR_IA32_VMX_PROCBASED_CTLS2 is only available "If
(CPUID.01H:ECX.[5] && IA32_VMX_PROCBASED_CTLS[63])". It was found that
some old cpus (namely "Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz (family: 0x6,
model: 0xf, stepping: 0x6") don't have it. Add the missing check.

Reported-by: Zdenek Kaspar <zkaspar82@...il.com>
Tested-by: Zdenek Kaspar <zkaspar82@...il.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/vmx/nested.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 653830d0f3da..4bd0902bfd8c 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5557,9 +5557,11 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps,
 	 * secondary cpu-based controls.  Do not include those that
 	 * depend on CPUID bits, they are added later by vmx_cpuid_update.
 	 */
-	rdmsr(MSR_IA32_VMX_PROCBASED_CTLS2,
-		msrs->secondary_ctls_low,
-		msrs->secondary_ctls_high);
+	if (msrs->procbased_ctls_high & CPU_BASED_ACTIVATE_SECONDARY_CONTROLS)
+		rdmsr(MSR_IA32_VMX_PROCBASED_CTLS2,
+		      msrs->secondary_ctls_low,
+		      msrs->secondary_ctls_high);
+
 	msrs->secondary_ctls_low = 0;
 	msrs->secondary_ctls_high &=
 		SECONDARY_EXEC_DESC |
-- 
2.20.1