Re: [PATCH 7/8] Implement smp_processor_id() with the PDA.

Jeremy Fitzhardinge
2006-08-31T16:04:33Z

Ian Campbell wrote:
> This doesn't compile for me if CONFIG_SMP=n
>

Ah, good point.

> LD .tmp_vmlinux1
> arch/i386/kernel/built-in.o: In function `cpu_init':
> (.init.text+0x1eda): undefined reference to `early_smp_processor_id'
> arch/i386/kernel/built-in.o: In function `cpu_init':
> (.init.text+0x1f11): undefined reference to `early_smp_processor_id'
>
> smp_processor_id() is defined for !SMP in include/linux/smp.h, I don't
> know if it would be appropriate to add early_smp_processor_id() there
> since it seems i386 specific. asm/smp.h isn't included by linux/smp.h
> when !SMP but you could add an explicit include to common.c I suppose.
>

I'll have a look.

I think my preferred solution would be to get rid of all the early*
stuff, and try to arrange to have the PDA set up before C code gets
run. For the boot CPU, it really could be done statically (I'm not
quite sure why the boot CPU's GDT is allocated, given that it already
has a static one; I think this might have been a Xen-related change?).
The secondary CPUs could have their GDT+PDA completely allocated and
initialized in advance, making secondary CPU PDA setup just a matter of
doing lgdt and setting %gs in head.S, even before hitting C code.

J