Re: [PATCH v5 06/39] x86/fpu: Add helper for modifying xstate

Edgecombe, Rick P
2023-02-01T17:32:45Z

On Wed, 2023-02-01 at 12:01 +0100, Borislav Petkov wrote:
> On Thu, Jan 19, 2023 at 01:22:44PM -0800, Rick Edgecombe wrote:
> > +void fpregs_lock_and_load(void)
> > +{
> > + /*
> > + * fpregs_lock() only disables preemption (mostly). So
> > modifying state
> > + * in an interrupt could screw up some in progress fpregs
> > operation,
> > + * but appear to work. Warn about it.
>
> I don't like comments where it sounds like we don't know what we're
> doing. "Appear to work"?

I can change it. This patch started with the observation that modifying
xstate from the kernel had been gotten wrong a couple times in the
past, so that is what this is referencing. Since then, the fancy
automatic solution got boiled down to this helper and a couple
warnings.