linux-kernel - [PATCH tip: x86/bugs v2] x86/mce: make sure cmci banks are cleared during shutdown on intel

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Message-ID: <20250627174935.95194-1-inwardvessel@gmail.com>
Date: Fri, 27 Jun 2025 10:49:35 -0700
From: JP Kobryn <inwardvessel@...il.com>
To: tony.luck@...el.com,
	bp@...en8.de,
	tglx@...utronix.de,
	mingo@...hat.com,
	dave.hansen@...ux.intel.com,
	hpa@...or.com,
	aijay@...a.com
Cc: linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	kernel-team@...a.com
Subject: [PATCH tip: x86/bugs v2] x86/mce: make sure cmci banks are cleared during shutdown on intel

CMCI banks are not cleared during shutdown on intel CPU's. As a side effect
when a kexec is performed, CPU's coming back online are unable to
rediscover/claim these occupied banks which breaks MCE reporting.

Clear the CPU ownership during shutdown via cmci_clear() so the banks can
be reclaimed and MCE reporting will become functional once more.

Signed-off-by: JP Kobryn <inwardvessel@...il.com>
Reported-by: Aijay Adams <aijay@...a.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
---
 arch/x86/kernel/cpu/mce/intel.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/mce/intel.c b/arch/x86/kernel/cpu/mce/intel.c
index efcf21e9552e..9b149b9c4109 100644
--- a/arch/x86/kernel/cpu/mce/intel.c
+++ b/arch/x86/kernel/cpu/mce/intel.c
@@ -478,6 +478,7 @@ void mce_intel_feature_init(struct cpuinfo_x86 *c)
 void mce_intel_feature_clear(struct cpuinfo_x86 *c)
 {
 	intel_clear_lmce();
+	cmci_clear();
 }
 
 bool intel_filter_mce(struct mce *m)
-- 
2.47.1