Re: [PATCH v2 06/39] x86/fpu: Add helper for modifying xstate

Edgecombe, Rick P
2022-10-04T16:14:45Z

On Tue, 2022-10-04 at 07:18 -0700, Dave Hansen wrote:
> On 10/3/22 13:05, Edgecombe, Rick P wrote:
> > The CET state is xsaves managed. It gets lazily restored before
> > returning to userspace with the rest of the fpu stuff. This
> > function
> > will force restore all the fpu state to the registers early and
> > lock
> > them from being automatically saved/restored. Then the tasks CET
> > state
> > can be modified in the MSRs, before unlocking the fpregs. Last time
> > I
> > tried to modify the state directly in the xsave buffer when it was
> > efficient, but it had issues and Thomas suggested this.
>
> Can you get the gist of this in a comment, please?

Sure.