On Wed, Jul 15, 2020 at 05:48:56PM +0200, Joerg Roedel wrote: > It is actually the CPUID instructions that cause #VC exceptions. The > MSRs that are accessed on AMD processors are not intercepted in the > hypervisors this code has been tested on, so these will not cause #VC > exceptions. 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 -- Kees Cook
