Re: [PATCH] hw/arm/virt: Fix CPU's default NUMA node ID

[Peter Maydell]

On Wed, 26 Jan 2022 at 09:14, Igor Mammedov <imammedo@redhat.com> wrote:
>
> On Wed, 26 Jan 2022 13:24:10 +0800
> Gavin Shan <gshan@redhat.com> wrote:
> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > index 141350bf21..b4a95522d3 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -2499,7 +2499,7 @@ virt_cpu_index_to_props(MachineState *ms, unsigned 
> > cpu_index)
> >
> >  static int64_t virt_get_default_cpu_node_id(const MachineState *ms, int 
> > idx)
> >  {
> > -    return idx % ms->numa_state->num_nodes;
> > +    return idx / (ms->smp.dies * ms->smp.clusters * ms->smp.cores * 
> > ms->smp.threads);
>
> I'd like for ARM folks to confirm whether above is correct
> (i.e. socket is NUMA node boundary and also if above topo vars
> could have odd values. Don't look at horribly complicated x86
> as example, but it showed that vendors could stash pretty much
> anything there, so we should consider it here as well and maybe
> forbid that in smp virt-arm parser)

Is there anybody on the CC list who can answer this definitively?
Certainly I have no idea about this virtual topology stuff --
from my point of view I just want VMs to be able to have
multiple CPUs and I don't know anything about how real hardware
might choose to do NUMA topology either now or in future...

Put another way: this patch isn't on my list to do anything with;
please ping me when a decision has been made about whether it should
be applied or not.

thanks
-- PMM