This change affects Intel CPUs only. As most platforms are doing
uCode update using FIT, they aren't affected by this code either.
Update microcode in MP-init using a single spinlock when running on
a Hyper-Threading enabled CPU on pre FIT platforms.
This will slow down the MP-init boot flow.
Intel SDM and various BWGs specify to use a semaphore to update
microcode on one thread per core on Hyper-Threading enabled CPUs.
Due to this complex code would be necessary to determine the core #ID,
initializing and picking the right semaphore out of CONFIG_MAX_CPUS / 2.
Instead use the existing global spinlock already present in MPinit code.
Assuming that only pre-FIT platforms with Hyper-Threading enabled and at
most 8 threads will ever run into this condition, the boot delay is
negligible.
This change is a counterproposal to the previous published patch series
being much more unsophisticated.
Change-Id: I27bf5177859c12e92d6ce7a2966c965d7262b472
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49303
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
ce51b34186