Re: [PATCH] Make math_state_restore() save and restore the interruptflag

From: H. Peter Anvin
Date: Sat Feb 01 2014 - 20:58:23 EST

On 02/01/2014 05:51 PM, Linus Torvalds wrote:
> On Sat, Feb 1, 2014 at 5:47 PM, Suresh Siddha <sbsiddha@xxxxxxxxx> wrote:
>> So if the restore failed, we should do something like drop_init_fpu(),
>> which will restore init-state to the registers.
>> for eager-fpu() paths we don't use clts() stts() etc.
> Uhhuh. Ok.
> Why do we do that, btw? I think it would make much more sense to just
> do what I *thought* we did, and just make it a context-switch-time
> optimization ("let's always switch FP state"), not make it a huge
> semantic difference.

Twiddling CR0.TS is pretty slow if we're not taking advantage of it.


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