Re: Per-cpu patches on top of PDA stuff...

[Rusty Russell <rusty@rustcorp.com.au>]

On Tue, 2006-09-19 at 01:14 -0700, Jeremy Fitzhardinge wrote:
> Rusty Russell wrote:
> > 	The first patch simply changes the GDTs to be a straight per-cpu
> > variable.  I notice that you did a similar thing with your patches, but
> > this is simpler and avoids wasting space in the UP case.  It's a bit
> > tricky since we've never referred to per-cpu vars from asm before, but
> > since we're only referring to the pre-setup versions, it's ok.
> >   
> 
> The current mechanism was specifically introduced by James Bottomley a 
> while back; I guess to deal with Voyager strangeness.

(James CC'd).  I dislike the gratuitous copy: we have three gdts, the
boot GDT, the master GDT (cpu_gdt_table), then the per-cpu GDT.  Using
the per-cpu mechanisms already in place makes it simple, avoids manual
allocation, and the extra master GDT.  The extra GDT is particularly
embarrassing on UP, which doesn't want a per-cpu GDT anyway...

Seems that we can't assume boot CPU == 0.  I think I've removed the two
places where I assumed that, but will need testing.

> Hm, now is not really a good time.  I'm still trying to get Xen 
> basically working, and the percpu PDA stuff isn't really necessary for 
> that.  The PDA stuff was enough of a problem in itself...
> 
> Also, the PDA patches are in -mm, so that's probably a better base for 
> your patches.

Yes, it turned out to be easier to go straight to -mm anyway.  I'll redo
them as Andi requested....

Rusty.
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