[PATCH v2 02/16] x86/mce: WARN once if IA32_FEATURE_CONTROL MSR is left unlocked

From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Tony Luck <tony.luck@intel.com>, Borislav Petkov <bp@alien8.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>,
	kvm@vger.kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>
Subject: [PATCH v2 02/16] x86/mce: WARN once if IA32_FEATURE_CONTROL MSR is left unlocked
Date: Mon, 21 Oct 2019 16:56:42 -0700	[thread overview]
Message-ID: <20191021235642.418-1-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20191021234632.32363-1-sean.j.christopherson@intel.com>

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

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.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

