Messages in this thread | | | Date | Sat, 01 Feb 2014 11:35:50 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] Make math_state_restore() save and restore the interrupt flag |
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On 02/01/2014 11:27 AM, Linus Torvalds wrote: > > (a) "we don't want to restore at all, because once the kernel starts > using math, it might do so a lot, and saving/restoring is a bad idea": > > void __kernel_fpu_end(void) > { > stts(); > } > > *or* > > Quite frankly, I'd almost lean towards (a). Comments? Does anybody > have any loads where the kernel does a lot of fpu stuff (ie network > encryption using the hw engines or something)? I'd really like to hear > if it makes a difference.. >
This will obviously not protect eageronly features (MPX, LWP, ...) so this means those features are permanently unavailable to the kernel, even inside kernel_fpu_begin/end. Now, currently I don't think we have any plans to use those in the kernel (at least not in a way where kernel_fpu_begin/end makes sense as bracketing), but it is something worth keeping in mind.
-hpa
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