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

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Date:   Sat, 10 Dec 2016 20:09:06 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        "Charles (Chas) Williams" <ciwillia@...cade.com>,
        "M. Vefa Bicakci" <m.v.b@...box.com>,
        Alok Kataria <akataria@...are.com>,
        xen-devel <xen-devel@...ts.xen.org>,
        Juergen Groß <jgross@...e.com>
Subject: Re: [PATCH] x86/smpboot: Make logical package management more
 robust

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.

> 2-node AMD box doesn't have these problems.
> 
> I haven't upgraded the Intel machine for about a month but this all must have
> happened in 4.9 timeframe.
> 
> So I can't answer your question since we clearly have other problems on Xen. I
> will be looking into this.

Fair enough. What you could do though with this patch applied and the extra
XEN call to topology_update_package_map() removed is to watchout for the
following messages:

  pr_info("Max logical packages: %u\n", __max_logical_packages);

and

  pr_warn(CPU %u Converting physical %u to logical package %u\n", ...)

Ideally the latter wont show.

Thanks,

	tglx