linux-kernel - [PATCH] x86/mce: Check for hypervisor before enabling additional error logging

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Date:   Mon, 9 Nov 2020 15:24:02 -0800
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>, Jim Mattson <jmattson@...gle.com>
Cc:     Qian Cai <cai@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-tip-commits@...r.kernel.org" 
        <linux-tip-commits@...r.kernel.org>, Boris Petkov <bp@...en8.de>,
        Borislav Petkov <bp@...e.de>, x86 <x86@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: [PATCH] x86/mce: Check for hypervisor before enabling additional
 error logging

Booting as a guest under KVM results in error messages about
unchecked MSR access:

[    6.814328][    T0] unchecked MSR access error: RDMSR from 0x17f at rIP: 0xffffffff84483f16 (mce_intel_feature_init+0x156/0x270)

because KVM doesn't provide emulation for random model specific registers.

Check for X86_FEATURE_HYPERVISOR and skip trying to enable the mode (a
guest shouldn't be concerned with corrected errors anyway).

Reported-by: Qian Cai <cai@...hat.com>
Fixes: 68299a42f842 ("x86/mce: Enable additional error logging on certain Intel CPUs")
Signed-off-by: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/cpu/mce/intel.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/mce/intel.c b/arch/x86/kernel/cpu/mce/intel.c
index b47883e364b4..7f7d863400b7 100644
--- a/arch/x86/kernel/cpu/mce/intel.c
+++ b/arch/x86/kernel/cpu/mce/intel.c
@@ -517,6 +517,9 @@ static void intel_imc_init(struct cpuinfo_x86 *c)
 {
 	u64 error_control;
 
+	if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
+		return;
+
 	switch (c->x86_model) {
 	case INTEL_FAM6_SANDYBRIDGE_X:
 	case INTEL_FAM6_IVYBRIDGE_X:
-- 
2.21.1