Re: [GIT PULL] x86 fixes

H. Peter Anvin
2015-08-19T10:00:47Z

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