x86/mce: Ensure user polling settings are honored when restarting timer

commit 00c092de upstream.

Users can disable MCA polling by setting the "ignore_ce" parameter or by
setting "check_interval=0". This tells the kernel to *not* start the MCE
timer on a CPU.

If the user did not disable CMCI, then storms can occur. When these
happen, the MCE timer will be started with a fixed interval. After the
storm subsides, the timer's next interval is set to check_interval.

This disregards the user's input through "ignore_ce" and
"check_interval". Furthermore, if "check_interval=0", then the new timer
will run faster than expected.

Create a new helper to check these conditions and use it when a CMCI
storm ends.

  [ bp: Massage. ]

Fixes: 7eae17c4 ("x86/mce: Add per-bank CMCI storm mitigation")
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/20250624-wip-mca-updates-v4-2-236dd74f645f@amd.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>