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Subject: Re: [GIT PULL] x86 fixes
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Mon, 17 Aug 2015 17:01:13 -0700
To: Andy Lutomirski <luto@amacapital.net>, Ingo Molnar <mingo@kernel.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>,
        Juergen Gross <jgross@suse.com>, Andy Lutomirski <luto@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Brian Gerst <brgerst@gmail.com>, Denys Vlasenko <dvlasenk@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>
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I ran a hacked Qemu with FPU off.

On August 17, 2015 4:59:18 PM PDT, Andy Lutomirski <luto@amacapital.net> wrote:
>On Mon, Aug 17, 2015 at 1:01 AM, Ingo Molnar <mingo@kernel.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

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