[XS] Change in coreboot[main]: soc/intel/meteorlake: Enable SSE2 accelerated RSA sign. verification

[Subrata Banik (Code Review)]

Attention is currently required from: Dinesh Gehlot, Eran Mitrani, Jakub Czapiga, Jérémy Compostella, Kapil Porwal, Tarun.

Subrata Banik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/79291?usp=email )

Change subject: soc/intel/meteorlake: Enable SSE2 accelerated RSA sign. verification
......................................................................

Patch Set 10:

(1 comment)

Patchset:

PS4:
> > unfortunately, I don't see any savings after picking this cl.
>
> Are you sure you have the vboot repository up-to-date in your build environment ?

except this CL, all other Cls are now landed in downstream (including coreboot, vboot project). I have picked this CL and performed 20 cycles. I don't see 5ms savings in run to run variation.
> Also the benefit is very small compared to the whole boot flow so you need an appropriate performance analysis methodology if you want to observe the benefit on the overall boot time in clear manner. Personally, I collect 20 warm reset `cbmem -t` logs. For those 20 logs, I generate the median of each time interval. Then I compare those.
>
> However, I you look at the the 505-506 interval which is when `modexp` is executed, you should observe a solid and systematic improvement of about 4.8 ms.
>
> I just re-did my boot performance analysis described above twice. In both cases I observe an overall boot time improvement. One is of 3.6 ms and the other of 9 ms.
>
> Note that the improvement is bit lower than it used to be. This is because only two RSA verification are performed now instead of 3. It seems to have changed in the last few months. I have updated the commit message accordingly.