Re: [Qemu-devel] ARM CPU affinities

[Andrew Jones <drjones@redhat.com>]

On Mon, Sep 28, 2015 at 10:13:15AM +0100, Peter Maydell wrote:
> On 27 September 2015 at 22:28, Peter Crosthwaite
> <crosthwaitepeter@gmail.com> wrote:
> > Hi Peter,
> >
> > I am looking at this:
> >
> > static void arm_cpu_initfn(Object *obj)
> > {
> >     ...
> >     Aff1 = cs->cpu_index / ARM_CPUS_PER_CLUSTER;
> >     Aff0 = cs->cpu_index % ARM_CPUS_PER_CLUSTER;
> >     cpu->mp_affinity = (Aff1 << ARM_AFF1_SHIFT) | Aff0;
> >
> >
> > Should we push this up to the machine model? I am trying to fix a
> > machine where Aff1 of the one and only cluster is non-zero. The kernel
> > SMP support barfs when Aff1 is mismatched to whats in the DTB (CPU reg
> > property).
> >
> > I think this modulo 8 starting from 0:0 policy might be specific to mach-virt?
> 
> Yeah, it should be a CPU property if you need it to be something
> different. I think we just left it as a hardcoded thing until
> somebody needed it to be different.
> 
> NB that as the comment says KVM currently imposes its own numbering
> anyway -- if you care about that you need to get the kernel to
> support having userspace tell it about affinity numbering.

I've been thinking about picking this work up. Let me confirm first that
Pavel hasn't already, because, iirc, he was the last to look into it.
Pavel?

Thanks,
drew