Re: [PATCH v4 70/75] x86/head/64: Don't call verify_cpu() on starting APs

On Wed, Jul 15, 2020 at 12:49:23PM -0700, Kees Cook wrote:

Aaah. I see. Thanks for the details there. So ... can you add a bunch
more comments about why/when the new entry path is being used? I really
don't want to accidentally discover some unrelated refactoring down
the road (in months, years, unrelated to SEV, etc) starts to also skip
verify_cpu() on Intel systems. There had been a lot of BIOSes that set
this MSR to disable NX, and I don't want to repeat that pain: Linux must
never start an Intel CPU with that MSR set. :P

Understood :)

I added a comment above the label explaining why it is only used for
SEV-ES guests and pointing out the importance of running verify_cpu() on
all other systems, especially if they are Intel based.

Regards,

	Joerg