linux-kernel - [PATCH v2 02/16] x86/mce: WARN once if IA32_FEATURE

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Message-Id: <20191021235642.418-1-sean.j.christopherson@intel.com>
Date:   Mon, 21 Oct 2019 16:56:42 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Tony Luck <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [PATCH v2 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.

Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: Wanpeng Li <wanpengli@...cent.com>
Cc: Jim Mattson <jmattson@...gle.com>
Cc: kvm@...r.kernel.org
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