Re: [PATCH] x86/smpboot: Make logical package management more robust

[Boris Ostrovsky]

On 12/10/2016 02:13 PM, Thomas Gleixner wrote:
> On Sat, 10 Dec 2016, Thomas Gleixner wrote:
> > On Fri, 9 Dec 2016, Boris Ostrovsky wrote:
> > > On 12/09/2016 06:02 PM, Boris Ostrovsky wrote:
> > > > On 12/09/2016 05:06 PM, Thomas Gleixner wrote:
> > > > > On Thu, 8 Dec 2016, Thomas Gleixner wrote:
> > > > >
> > > > > Boris, can you please verify if that makes the
> > > > > topology_update_package_map() call which you placed into the Xen cpu
> > > > > starting code obsolete ?
> > > >
> > > > Will do. I did test your patch but without removing
> > > > topology_update_package_map() call. It complained about package IDs
> > > > being wrong, but that's expected until I fix Xen part.
> > >
> > > Ignore my statement about earlier testing --- it was all on single-node
> > > machines.
> > >
> > > Something is broken with multi-node on Intel, but failure modes are different.
> > > Prior to this patch build_sched_domain() reports an error and pretty soon we
> > > crash in scheduler (don't remember off the top of my head). With patch applied
> > > I crash mush later, when one of the drivers does kmalloc_node(..,
> > > cpu_to_node(cpu)) and cpu_to_node() returns 1, which should never happen
> > > ("x86: Booted up 1 node, 32 CPUs" is reported, for example).
> >
> > Hmm. But the cpu_to_node() association is unrelated to the logical package
> > management.
>
> Just came to my mind after hitting send. We had the whole persistent cpuid
> to nodeid association work merged in 4.9. So that might be related.


Yes, that's exactly the reason.

It uses _PXM to set nodeID and _PXM is exposed to dom0 (which is a 
privileged PV guest).

Re: you previous message: after I "fix" the problem above,  I see
    pr_info("Max logical packages: %u\n", __max_logical_packages);
but no
    pr_warn(CPU %u Converting physical %u to logical package %u\n", ...)

with or without topology_update_package_map() in 
arch/x86/xen/smp.c:cpu_bringup()


-boris