[PATCH v3 05/19] x86/mce: WARN once if IA32_FEATURE_CONTROL MSR is left unlocked

[Sean Christopherson]

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

Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
 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 3e5b29acd301..5abc55a67fce 100644
--- a/arch/x86/kernel/cpu/mce/intel.c
+++ b/arch/x86/kernel/cpu/mce/intel.c
@@ -119,11 +119,10 @@ static bool lmce_supported(void)
 	 * generate a #GP fault.
 	 */
 	rdmsrl(MSR_IA32_FEATURE_CONTROL, tmp);
-	if ((tmp & (FEAT_CTL_LOCKED | FEAT_CTL_LMCE_ENABLED)) ==
-		   (FEAT_CTL_LOCKED | FEAT_CTL_LMCE_ENABLED))
-		return true;
+	if (WARN_ON_ONCE(!(tmp & FEAT_CTL_LOCKED)))
+		return false;
 
-	return false;
+	return tmp & FEAT_CTL_LMCE_ENABLED;
 }
 
 bool mce_intel_cmci_poll(void)
-- 
2.24.0