linux-kernel - Re: [GIT PULL] x86 fixes

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Message-ID: <20150818075520.GB32338@gmail.com>
Date:	Tue, 18 Aug 2015 09:55:20 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Juergen Gross <jgross@...e.com>,
	Andy Lutomirski <luto@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86 fixes


* Andy Lutomirski <luto@...capital.net> wrote:

> On Mon, Aug 17, 2015 at 1:01 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> > So when I re-introduced static allocations math-emu started working again, to 
> > a limited degree: on a modern distro, trying to boot /bin/bash I got a prompt, 
> > but various programs would segfault. I did not investigate it any deeper, I 
> > suppose the FPU emulation does not go far enough for modern user-space, or 
> > maybe it has more bugs.
> 
> Were you testing with just no387 or did you run a VM with SSE2 and such turned 
> off?
> 
> There's a *lot* of userspace that incorrectly checks for instructions without 
> checking for the state support.  I've filed bugs against libgcc for this and 
> they're still not fixed IIRC.

I tested relatively ancient user-space, 2007 era Fedora Core 6 - but I didn't 
check whether it's truly SSE-less (it probably isn't).

Thanks,

	Ingo
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