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

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Date:   Wed, 1 Feb 2023 17:31:50 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v5 06/39] x86/fpu: Add helper for modifying xstate

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.