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

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Message-ID: <20150221192352.GA10027@gmail.com>
Date:	Sat, 21 Feb 2015 20:23:52 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Rik van Riel <riel@...hat.com>, x86@...nel.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


* Borislav Petkov <bp@...en8.de> wrote:

> > I'd sleep a lot better if we had some runtime debug 
> > flag to be able to do run-to-run comparisons on the 
> > same booted up kernel, or so.
> 
> Let me take a look whether we could so some knob... The 
> nice thing is, code uses use_eager_fpu() to check stuff 
> so we should be able to clear the cpufeature flag.

Either that, or you could quickly hack those checks to use 
panic_timeout, add an 'extern int panic_timeout;' and after 
bootup do:

   echo 0 > /proc/sys/kernel/panic
   echo 1 > /proc/sys/kernel/panic

to switch between the modes?

Thanks,

	Ingo
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