Re: [RFC PATCH 04/10 v2 ] x86/fpu: eager switch PKRU state

[Paolo Bonzini]

On 18/09/2018 16:27, Sebastian Andrzej Siewior wrote:
>> Likewise, move this to fpu__clear and outside "if
>> (static_cpu_has(X86_FEATURE_FPU))"?
> okay. But if there is no FPU we did not save/restore the pkru value. Is
> this supposed to be an improvement?

Honestly it just seemed "more correct", but now that I think about it,
kernel threads should run with PKRU=0.  maybe there's a preexisting bug
that your patch has the occasion to fix.

Paolo

>> Also, a __read_pkru() seems to be missing in switch_fpu_prepare.
> But the value is stored during write_pkru(). So the copy that is saved
> should be identical to the value that would be read, correct?
>