Messages in this thread | | | Subject | Re: [PATCH] Make math_state_restore() save and restore the interrupt flag | From | "H. Peter Anvin" <> | Date | Sat, 01 Feb 2014 18:12:18 -0800 |
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Yes, that is exactly the "eageronly" features - currently LWP and MPX.
On February 1, 2014 6:05:05 PM PST, Linus Torvalds <torvalds@linux-foundation.org> wrote: >On Sat, Feb 1, 2014 at 5:57 PM, H. Peter Anvin <hpa@zytor.com> wrote: >> >> Twiddling CR0.TS is pretty slow if we're not taking advantage of it. > >Immaterial. > >We *already* avoid twiddling TS if it's not needed. > >It is true that we used to twiddle it at every context switch (and >then twiddle it *again* if we decided that we'd want to pre-load the >FPU state anyway, and avoid the extra fault). > >But that was fixed, and if we switch from a task that had math state >to another task that has math state, we leave TS alone. > >But Suresh apparently hits on the real issue: > >> not all the state under xsave adhers to cr0.TS/DNA rules > >which if so is sad but yes, makes CR0.TS no longer sufficient. > > Linus
-- Sent from my mobile phone. Please pardon brevity and lack of formatting.
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