Subject: Re: [GIT PULL] x86 fixes
To: Ingo Molnar <mingo@kernel.org>
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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>
From: "H. Peter Anvin" <hpa@zytor.com>
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Date: Wed, 19 Aug 2015 03:00:16 -0700
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On 08/18/15 23:50, Ingo Molnar wrote:
>
> Ah, so I was able to make math-emu work with the 'no387 nofxsr' boot options.
>
> It turns out that the crash happens due 'no387' not turning off all modern FPU
> features in cpufeatures, which confuses the FPU code. (This is a far less severe
> bug than math emu not working at all.)
>
> I get some instances of:
>
>     /etc/rc3.d/S99local: line 26:  1626 Illegal instruction
>
> due to user-space presuming modern FPU capabilities:
>

And I bet if CPUID actually reported the right thing it probably would 
work okay.  As I said, I tested this under Qemu which reported an 
accurate (lack of) CPUID for a 486SX.

	-hpa


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