linux-kernel - [PATCH 3.16 148/202] x86/kvm/nVMX: read from MSR_IA32_VMX_PROCBASED

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Message-ID: <lsq.1556377989.569842885@decadent.org.uk>
Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Jim Mattson" <jmattson@...gle.com>,
        "Vitaly Kuznetsov" <vkuznets@...hat.com>,
        "Zdenek Kaspar" <zkaspar82@...il.com>,
        "Paolo Bonzini" <pbonzini@...hat.com>
Subject: [PATCH 3.16 148/202] x86/kvm/nVMX: read from MSR_IA32_VMX_PROCBASED_CTLS2
 only when it is available

3.16.66-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vitaly Kuznetsov <vkuznets@...hat.com>

commit 6b1971c694975e49af302229202c0043568b1791 upstream.

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>
Reviewed-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
[bwh: Backported to 3.16:
 - The MSR values are stored in static variables
 - Adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2320,8 +2320,11 @@ static __init void nested_vmx_setup_ctls
 	nested_vmx_procbased_ctls_high |= CPU_BASED_USE_MSR_BITMAPS;
 
 	/* secondary cpu-based controls */
-	rdmsr(MSR_IA32_VMX_PROCBASED_CTLS2,
-		nested_vmx_secondary_ctls_low, nested_vmx_secondary_ctls_high);
+	if (nested_vmx_procbased_ctls_high & CPU_BASED_ACTIVATE_SECONDARY_CONTROLS)
+		rdmsr(MSR_IA32_VMX_PROCBASED_CTLS2,
+		      nested_vmx_secondary_ctls_low,
+		      nested_vmx_secondary_ctls_high);
+
 	nested_vmx_secondary_ctls_low = 0;
 	nested_vmx_secondary_ctls_high &=
 		SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |