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

[Suresh Siddha]

On Sat, Feb 1, 2014 at 5:51 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> 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.

clts/stts is more costly and not all the state under xsave adhers to
cr0.TS/DNA rules.

did I answer your question?

thanks,
suresh
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