Re: [PATCH 4/8] unify paravirt parts of system.h

[Pavel Machek <pavel@ucw.cz>]

On Tue 2007-12-04 20:34:32, Andi Kleen wrote:
> On Tue, Dec 04, 2007 at 09:18:33PM +0200, Avi Kivity wrote:
> > Glauber de Oliveira Costa wrote:
> >> This patch moves the i386 control registers manipulation functions,
> >> wbinvd, and clts functions to system.h. They are essentially the same
> >> as in x86_64, except for the cr8 register, which we add.
> >>
> >> +
> >> +static inline unsigned long native_read_cr8(void)
> >> +{
> >> +	unsigned long cr8;
> >> +	asm volatile("mov %%cr8,%0" : "=r" (cr8), "=m" (__force_order));
> >> +	return cr8;
> >> +}
> >> +
> >>   
> >
> > There is no cr8 register on i386.  This had better be protected by an 
> > #ifdef.
> >
> > (you're likely not getting an error since it's a static inline, so the asm 
> > is never emitted)
> 
> Linux never uses that register. The only user is suspend save/restore, 
> but that' bogus because it wasn't ever initialized by Linux in the first
> place. It could be probably all safely removed.

It probably is safe to remove... but we currently support '2.8.95
kernel loads/resumes 2.6.24 image'... which would break if 2.8 uses
cr8.

So please keep it if it is not a big problem.

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