x86/mce: Handle Intel threshold interrupt storms

x86/mce: Handle Intel threshold interrupt storms

Add an Intel specific hook into machine_check_poll() to keep track of
per-CPU, per-bank corrected error logs (with a stub for the
CONFIG_MCE_INTEL=n case).

When a storm is observed the rate of interrupts is reduced by setting
a large threshold value for this bank in IA32_MCi_CTL2. This bank is
added to the bitmap of banks for this CPU to poll. The polling rate is
increased to once per second.

When a storm ends reset the threshold in IA32_MCi_CTL2 back to 1, remove
the bank from the bitmap for polling, and change the polling rate back
to the default.

If a CPU with banks in storm mode is taken offline, the new CPU that
inherits ownership of those banks takes over management of storm(s) in
the inherited bank(s).

The cmci_discover() function was already very large. These changes
pushed it well over the top. Refactor with three helper functions to
bring it back under control.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231115195450.12963-4-tony.luck@intel.com