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Message-ID: <DF2DA6AB-77F7-4A87-A84A-83A55DF688DC@zytor.com>
Date: Mon, 17 Aug 2015 17:01:13 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Andy Lutomirski <luto@...capital.net>,
Ingo Molnar <mingo@...nel.org>
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>,
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
I ran a hacked Qemu with FPU off.
On August 17, 2015 4:59:18 PM PDT, 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.
>
>--Andy
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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