Re: xen on suse 9.3 and software raid

[Gerd Knorr <kraxel@bytesex.org>]

[ adding xen-devel to Cc: ]

> Just loading the raid6 module in a xen domain makes my
> machine oops, log below.  I'd guess it's because the
> module attempts to use mmx within the kernel, which is
> a bit tricky because you have to save/restore userspace
> fp state for that.  Could be a corner case which simply
> doesn't work with xen.

Confirmed, the faulting instruction is a attempt to access
cr0, right here:

  static inline unsigned long raid6_get_fpu(void)
  {
          unsigned long cr0;

          preempt_disable();
          asm volatile("mov %%cr0,%0 ; clts" : "=r" (cr0));
          return cr0;
  }

(which is called by raid6_before_mmx, which in turn is called by
raid6_mmx1_gen_syndrome, both calls not visible in the trace
because they are inlined).

Ideas how to fix that?  Other than just disabling raid6?  Can
that code be replaced with xen hypercalls?  fsave & frestore
are also used btw.  It's all in drivers/md/raid6x86.h

  Gerd

-- 
-mm seems unusually stable at present.
	-- akpm about 2.6.12-rc3-mm3