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

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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