[PATCH v4 05/19] x86/mce: WARN once if IA32_FEAT_CTL MSR is left unlocked

Sean Christopherson
2019-11-28T01:42:01Z

WARN if the IA32_FEAT_CTL MSR is somehow left unlocked now that CPU
initialization unconditionally locks the MSR.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kernel/cpu/mce/intel.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/intel.c b/arch/x86/kernel/cpu/mce/intel.c
index c238518b84a2..5627b1091b85 100644
--- a/arch/x86/kernel/cpu/mce/intel.c
+++ b/arch/x86/kernel/cpu/mce/intel.c
@@ -116,14 +116,15 @@ static bool lmce_supported(void)
/*
* BIOS should indicate support for LMCE by setting bit 20 in
* IA32_FEAT_CTL without which touching MCG_EXT_CTL will generate a #GP
- * fault.
+ * fault. The MSR must also be locked for LMCE_ENABLED to take effect.
+ * WARN if the MSR isn't locked as init_ia32_feat_ctl() unconditionally
+ * locks the MSR in the event that it wasn't already locked by BIOS.
*/
rdmsrl(MSR_IA32_FEAT_CTL, 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