linux-kernel - Re: [PATCH RFC 4/5] x86,fpu: lazily skip FPU restore when still loaded

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Message-ID: <57F2C467.5060007@linux.intel.com>
Date:   Mon, 3 Oct 2016 13:49:43 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, tglx@...utronix.de, pbonzini@...hat.com,
        mingo@...hat.com, luto@...nel.org, hpa@...or.com, bp@...e.de
Subject: Re: [PATCH RFC 4/5] x86,fpu: lazily skip FPU restore when still
 loaded

On 10/03/2016 01:22 PM, Rik van Riel wrote:
>> > What are the preempt rules with this thing?  This needs to be called
>> > in preempt-disabled contexts, right?
> Indeed, all the FPU context switching code needs 
> to be called in preempt-disabled contexts.
> 
> You do not want to get preempted halfway through
> saving or restoring floating point registers.

OK, cool, that's what I expected.  Could you just add a comment about it
to make it clear that it's also the case for this new
fpu_lazy_skip_restore() helper?