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

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Date:   Sat, 10 Dec 2016 22:23:45 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Thomas Gleixner <tglx@...utronix.de>
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 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