linux-kernel - [PATCH 02/16] x86/mce: WARN once if IA32_FEATURE

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Date:   Fri,  4 Oct 2019 14:56:01 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Tony W Wang-oc <TonyWWang-oc@...oxin.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-edac@...r.kernel.org,
        Borislav Petkov <bp@...e.de>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH 02/16] x86/mce: WARN once if IA32_FEATURE_CONTROL MSR is left unlocked

WARN if the IA32_FEATURE_CONTROL MSR is somehow left unlocked now that
CPU initialization unconditionally locks the MSR.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kernel/cpu/mce/intel.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/intel.c b/arch/x86/kernel/cpu/mce/intel.c
index 88cd9598fa57..1008f14b803b 100644
--- a/arch/x86/kernel/cpu/mce/intel.c
+++ b/arch/x86/kernel/cpu/mce/intel.c
@@ -117,11 +117,10 @@ static bool lmce_supported(void)
 	 * generate a #GP fault.
 	 */
 	rdmsrl(MSR_IA32_FEATURE_CONTROL, tmp);
-	if ((tmp & (FEATURE_CONTROL_LOCKED | FEATURE_CONTROL_LMCE)) ==
-		   (FEATURE_CONTROL_LOCKED | FEATURE_CONTROL_LMCE))
-		return true;
+	if (WARN_ON_ONCE(!(tmp & FEATURE_CONTROL_LOCKED)))
+		return false;
 
-	return false;
+	return tmp & FEATURE_CONTROL_LMCE;
 }
 
 bool mce_intel_cmci_poll(void)
-- 
2.22.0