x86/microcode: Handle "offline" CPUs correctly

mainline inclusion
from mainline-v6.7-rc1
commit 8f849ff63bcbc77670da03cb8f2b78b06257f455
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I8XRMW


CVE: NA

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

Offline CPUs need to be parked in a safe loop when microcode update is
in progress on the primary CPU. Currently, offline CPUs are parked in
mwait_play_dead(), and for Intel CPUs, its not a safe instruction,
because the MWAIT instruction can be patched in the new microcode update
that can cause instability.

  - Add a new microcode state 'UCODE_OFFLINE' to report status on per-CPU
  basis.
  - Force NMI on the offline CPUs.

Wake up offline CPUs while the update is in progress and then return
them back to mwait_play_dead() after microcode update is complete.

Intel-SIG: commit 8f849ff63bcb x86/microcode: Handle "offline" CPUs correctly.
Microcode restructuring backport.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231002115903.660850472@linutronix.de


[ Aubrey Li: amend commit log ]
Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>