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Date: Sat, 01 Feb 2014 18:12:18 -0800 From: "H. Peter Anvin" <hpa@...or.com> To: Linus Torvalds <torvalds@...ux-foundation.org> CC: Suresh Siddha <sbsiddha@...il.com>, Nate Eldredge <nate@...tsmathematics.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, the arch/x86 maintainers <x86@...nel.org>, stable <stable@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Maarten Baert <maarten-baert@...mail.com>, Jan Kara <jack@...e.cz>, George Spelvin <linux@...izon.com>, Pekka Riikonen <priikone@....fi> Subject: Re: [PATCH] Make math_state_restore() save and restore the interrupt flag Yes, that is exactly the "eageronly" features - currently LWP and MPX. On February 1, 2014 6:05:05 PM PST, Linus Torvalds <torvalds@...ux-foundation.org> wrote: >On Sat, Feb 1, 2014 at 5:57 PM, H. Peter Anvin <hpa@...or.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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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