[coreboot-gerrit] [M] Change in coreboot[master]: cpu/x86/cache: CLFLUSH programs to memory before running

[Arthur Heymans (Code Review)]

Attention is currently required from: Raul Rangel, Nico Huber, Michał Żygowski, Subrata Banik, Reka Norman, Michał Kopeć, Angel Pons, Felix Held.

Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/37196 )

Change subject: cpu/x86/cache: CLFLUSH programs to memory before running
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Patch Set 23:

(1 comment)

Patchset:

PS23:
> > > > will this config also helps Xeon platforms?
> > >
> > > It should help all Intel platform that supports CLFLUSH IMO.
> >
> > Well on SPR xeon-sp against recommendations TempRamExit was overloaded with functionality to write things to DRAM to speed things up and therefore made mandatory in the bootflow. CLFLUSHING would have been a way better solution, as invalidating cache in a different environment (FSP) is just though to get right even from a security perspective...
>
> ah, i missed that SPR is still using FSP-T

CAR setup is indeed quite complicated on Xeon-SP and requires FSP-T for now (coherency needs to be set up across CPUs). However CAR teardown is the same as (e)NEM. On CPX and SKX coreboot CAR teardown is used over FSP-M TempRamExit. On SPR-SP that's not possible anymore due to the modified bootflow.