Re: [Xen-merge] [PATCH] loosen write_cr0/4 restrictions

["Stephen C. Tweedie" <sct@xxxxxxxxxx>]

Hi,

On Thu, 2006-01-12 at 08:55 +0100, Jan Beulich wrote:

> I disagree with this change; it should rather be done similarly to the
> merge for x86-64's xor.h.

Whichever way it's done, we definitely don't want to preserve the
WARN_ON():

> -#define write_cr0(x) BUG()
> +#define write_cr0(x) \
> +     WARN_ON(1); \
> +     __asm__ __volatile__("movl %0,%%cr0": :"r" (x));

That will let the boot xor tests pass, but will result in massive
console spam if anybody actually uses raid5.  Better to fix it for good
right away, either by relying on the hypervisor %cr0 virtualisation or
just by doing a conditional stts() in the XMMS_RESTORE (the latter is
probably more efficient.)

--Stephen



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