[PATCH 6.18 237/430] x86/mce: Do not clear banks poll bit in mce_poll_banks on AMD SMCA systems

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Avadhut Naik <avadhut.naik@amd.com>

commit d7ac083f095d894a0b8ac0573516bfd035e6b25a upstream.

Currently, when a CMCI storm detected on a Machine Check bank, subsides, the
bank's corresponding bit in the mce_poll_banks per-CPU variable is cleared
unconditionally by cmci_storm_end().

On AMD SMCA systems, this essentially disables polling on that particular bank
on that CPU. Consequently, any subsequent correctable errors or storms will not
be logged.

Since AMD SMCA systems allow banks to be managed by both polling and
interrupts, the polling banks bitmap for a CPU, i.e., mce_poll_banks, should
not be modified when a storm subsides.

Fixes: 7eae17c4add5 ("x86/mce: Add per-bank CMCI storm mitigation")
Signed-off-by: Avadhut Naik <avadhut.naik@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20251121190542.2447913-2-avadhut.naik@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kernel/cpu/mce/threshold.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/mce/threshold.c
+++ b/arch/x86/kernel/cpu/mce/threshold.c
@@ -85,7 +85,8 @@ void cmci_storm_end(unsigned int bank)
 {
 	struct mca_storm_desc *storm = this_cpu_ptr(&storm_desc);
 
-	__clear_bit(bank, this_cpu_ptr(mce_poll_banks));
+	if (!mce_flags.amd_threshold)
+		__clear_bit(bank, this_cpu_ptr(mce_poll_banks));
 	storm->banks[bank].history = 0;
 	storm->banks[bank].in_storm_mode = false;