linux-kernel - Re: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs

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Date:	Mon, 23 Feb 2015 10:51:26 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Andy Lutomirski <luto@...capital.net>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Ingo Molnar <mingo@...nel.org>,
	Oleg Nesterov <oleg@...hat.com>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs

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On 02/23/2015 10:03 AM, Borislav Petkov wrote:
> On Mon, Feb 23, 2015 at 07:51:04AM -0500, Rik van Riel wrote:
>> At that point we either load the FPU context, or we set CR0.TS.
> 
> Right, but provided eager doesn't bring any slowdown, we can drop
> the TS fiddling altogether and only load FPU context.

Agreed.

However, we would still need the rest of the kernel code to
check whether userspace FPU context is loaded in the registers
or not. We cannot simplify to the point of assuming that the
FPU state will always be loaded when in eager mode.

- -- 
All rights reversed
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