Re: [PATCH 3/3] Gdt page isolation

[Andi Kleen]

On Thu, Sep 22, 2005 at 03:34:02PM +0200, Ingo Molnar wrote:
> 
> * Andi Kleen <ak@xxxxxx> wrote:
> 
> > >  	 * This grunge runs the startup process for
> > >  	 * the targeted processor.
> > >  	 */
> > > +	cpu_gdt_descr[cpu].address = __get_free_page(GFP_KERNEL|__GFP_ZERO);
> > 
> > I can see why don't check it for NULL, but it's a ugly reason and 
> > would be better fixed. It at least needs a comment.
> 
> it's so early in the bootup that any failure here would probably be 
> fatal anyway. But yeah, a comment would be nice.

Not true for AP boot, especially with CPU hotplug.
And CPU hotplug will be common because suspend/resume use it
and next years laptops will have dual core CPUs.
So it would be nicer to handle it. But getting out of that 
path is difficult.


> > -Andi (who would still prefer just going back to the array in head.S - 
> > would work as well and waste less memory)
> 
> that doesnt really solve the problem for e.g. Xen, which needs a 
> separate page for each GDT. (xenolinux is a separate arch right now, but 
> it will/should be merged back into its base architectures) So why not 
> solve all the problems at once?

Xen could use the same method vmware uses that handles having other
read only data in there too? Doesn't sound too bad.

-Andi
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