Re: [kvm-ppc-devel] [RFC PATCH] KVM for PowerPC: simpler TLB handling, better page management

[Hollis Blanchard <hollisb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

On Fri, 2008-02-01 at 13:07 -0600, Nathan Lynch wrote:
> Hollis Blanchard wrote:
> > --- a/arch/powerpc/kernel/asm-offsets.c
> > +++ b/arch/powerpc/kernel/asm-offsets.c
> > @@ -22,6 +22,7 @@
> >  #include <linux/mman.h>
> >  #include <linux/mm.h>
> >  #include <linux/suspend.h>
> > +#include <linux/kvm_host.h>
> >  #ifdef CONFIG_PPC64
> >  #include <linux/time.h>
> >  #include <linux/hardirq.h>
> > @@ -328,5 +329,31 @@ int main(void)
> >  
> >  	DEFINE(PGD_TABLE_SIZE, PGD_TABLE_SIZE);
> >  
> > +#ifdef CONFIG_KVM
> > +	DEFINE(TLBE_BYTES, sizeof(struct tlbe));
> > +
> > +	DEFINE(VCPU_HOST_STACK, offsetof(struct kvm_vcpu, arch.host_stack));
> > +	DEFINE(VCPU_HOST_PID, offsetof(struct kvm_vcpu, arch.host_pid));
> > +	DEFINE(VCPU_HOST_TLB, offsetof(struct kvm_vcpu, arch.host_tlb));
> > +	DEFINE(VCPU_SHADOW_TLB, offsetof(struct kvm_vcpu, arch.shadow_tlb));
> 
> I found that if CONFIG_KVM=m these definitions don't get picked up
> when generating asm-offsets.h, which causes the build to break:
> 
>   AS      arch/powerpc/kvm/booke_interrupts.o
> arch/powerpc/kvm/booke_interrupts.S: Assembler messages:
> arch/powerpc/kvm/booke_interrupts.S:347: Error: unsupported relocation
> against VCPU_HOST_TLB
> arch/powerpc/kvm/booke_interrupts.S:348: Error: unsupported relocation
> against VCPU_SHADOW_TLB
> make[1]: *** [arch/powerpc/kvm/booke_interrupts.o] Error 1
> 
> Changing it to ifdef CONFIG_KVM_POWERPC (which is a bool) seems to do
> the right thing.

Hmm... building as a module is something we've struggled with in the
past, so I just left KVM_POWERPC as a bool because I didn't want to mess
with it.

With PowerPC's asm-offsets dependency, is it really possible to build a
standalone module if the kernel didn't have KVM=y?

-- 
Hollis Blanchard
IBM Linux Technology Center


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