linux-kernel - Re: FPU emulation broken in 2.6.28-rc8 ?

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Date:	Thu, 18 Dec 2008 00:20:44 +0100 (CET)
From:	Jesper Juhl <jj@...osbits.net>
To:	Rogier Wolff <R.E.Wolff@...Wizard.nl>
cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: FPU emulation broken in 2.6.28-rc8 ?

On Wed, 17 Dec 2008, Rogier Wolff wrote:

> On Wed, Dec 17, 2008 at 11:45:39PM +0100, Andi Kleen wrote:
> > Rogier Wolff <R.E.Wolff@...Wizard.nl> writes:
> > >> 
> > >> I'm trying to set up a thin client, which runs on a geode, which
> > >> apparently doesn't have a FPU.... (/proc/cpuinfo mentions the flag 
> > >> "fpu", what does THAT mean?)
> > 
> > Geodes all have FPUs to my knowledge.
> > The only FPU less x87s are 386s and special 486s (and a few emulators)
> > 
> > If the FPU doesn't work on the Geode something else must be broken
> > (or your CPU is not really a Geode)
> 
> Although the /proc/cpuinfo file shows the FPU flag, the kernel stops
> with "no fpu found, and math emulation not present" if I disable
> FP emulation.... 
> 
> chipolata:/etc/X11# cat /proc/cpuinfo 
> processor       : 0
> vendor_id       : CyrixInstead
> cpu family      : 5
> model           : 9
> model name      : Geode(TM) Integrated Processor by National Semi
> stepping        : 2
> cpu MHz         : 299.913
> cache size      : 16 KB
> fdiv_bug        : yes
> hlt_bug         : no
> f00f_bug        : no
> coma_bug        : no
> fpu             : no
> fpu_exception   : no
> cpuid level     : 2
> wp              : yes
> flags           : fpu tsc msr cx8 cmov mmx cxmmx
> bogomips        : 599.82
> clflush size    : 32
> power management:
> 
I've got a box with a Geode CPU here (although a slightly newer one than 
yours) and it works fine without FPU/math emulation.

root@...mpdragon:~# cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 5
model           : 10
model name      : Geode(TM) Integrated Processor by AMD PCS
stepping        : 2
cpu MHz         : 499.894
cache size      : 128 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu de pse tsc msr cx8 sep pge cmov clflush mmx mmxext 3dnowext 3dnow up
bogomips        : 999.78
clflush size    : 32
power management:

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