linux-kernel - Re: [v6,3/3] x86/smpboot: Fix __max_logical

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Message-ID: <02ccc129-83b5-18e9-de5c-b3eff81a8f22@redhat.com>
Date:   Wed, 7 Feb 2018 14:31:02 -0500
From:   Prarit Bhargava <prarit@...hat.com>
To:     Simon Gaiser <simon@...isiblethingslab.com>,
        xen-devel <xen-devel@...ts.xen.org>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Piotr Luc <piotr.luc@...el.com>,
        Kan Liang <kan.liang@...el.com>, Borislav Petkov <bp@...e.de>,
        Stephane Eranian <eranian@...gle.com>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        He Chen <he.chen@...ux.intel.com>,
        Mathias Krause <minipli@...glemail.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [v6,3/3] x86/smpboot: Fix __max_logical_packages estimate



On 02/07/2018 02:26 PM, Simon Gaiser wrote:
> Prarit Bhargava:
>> On 02/07/2018 01:44 PM, Simon Gaiser wrote:

<snip>

>>> This breaks booting as Xen PV domain for me. The problem seems to be
>>> that native_smp_cpus_done() is never called on a PV domain. So
>>> __max_logical_packages is uninitialized and this leads to a NULL
>>> pointer dereference in coretemp.
>>>
>>
>> I'll see if I can figure out a way to test that.
> 
> Ok, thanks. If you need some logs, or if I should test something just
> ask.
> 

Thanks, I may send you a patch off-list to test.

>> Does 947134d9b00f
>> ("x86/smpboot: Do not use smp_num_siblings in __max_logical_packages
>> calculation") help?
> 
> No.
> 

Yeah, your description was absolutely correct.  native_smp_cpus_done() is only
called for HVM guests and not PV.  I'm going to think about that and send you a
patch in a bit.

P.