Messages in this thread | | | Date | Sat, 1 Feb 2014 17:59:00 -0800 | Subject | Re: [PATCH] Make math_state_restore() save and restore the interrupt flag | From | Suresh Siddha <> |
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On Sat, Feb 1, 2014 at 5:51 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > On Sat, Feb 1, 2014 at 5:47 PM, Suresh Siddha <sbsiddha@gmail.com> 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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