linux-kernel - [PATCH v2] x86/mce: Use "safe" MSR functions when enabling additional error logging

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Date:   Tue, 10 Nov 2020 16:39:54 -0800
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Borislav Petkov <bp@...en8.de>, Jim Mattson <jmattson@...gle.com>,
        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>, x86 <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: [PATCH v2] x86/mce: Use "safe" MSR functions when 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.

Switch to using rdmsrl_safe()/wrmsrl_safe() to avoid the message.

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 | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/intel.c b/arch/x86/kernel/cpu/mce/intel.c
index b47883e364b4..42e60ef16c3a 100644
--- a/arch/x86/kernel/cpu/mce/intel.c
+++ b/arch/x86/kernel/cpu/mce/intel.c
@@ -521,9 +521,10 @@ static void intel_imc_init(struct cpuinfo_x86 *c)
 	case INTEL_FAM6_SANDYBRIDGE_X:
 	case INTEL_FAM6_IVYBRIDGE_X:
 	case INTEL_FAM6_HASWELL_X:
-		rdmsrl(MSR_ERROR_CONTROL, error_control);
+		if (rdmsrl_safe(MSR_ERROR_CONTROL, &error_control))
+			return;
 		error_control |= 2;
-		wrmsrl(MSR_ERROR_CONTROL, error_control);
+		wrmsrl_safe(MSR_ERROR_CONTROL, error_control);
 		break;
 	}
 }
-- 
2.21.1