From: Ingo Molnar <mingo@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Joseph Salisbury <joseph.salisbury@canonical.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Andi Kleen <andi.kleen@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@amacapital.net>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Harish Chegondi <harish.chegondi@intel.com>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Kan Liang <kan.liang@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Luis R. Rodriguez" <mcgrof@suse.com>,
Stephane Eranian <eranian@google.com>,
Toshi Kani <toshi.kani@hp.com>,
Vince Weaver <vincent.weaver@maine.edu>,
LKML <linux-kernel@vger.kernel.org>,
yingying.zhao@intel.com, "Zhang,
Xiong Y" <xiong.y.zhang@intel.com>,
1573231@bugs.launchpad.net, 1397880@bugs.launchpad.net,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Chen Yucong <slaoub@gmail.com>,
Laura Abbott <labbott@fedoraproject.org>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
David Vrabel <david.vrabel@citrix.com>
Subject: Re: [v4.6-rc1 Regression] x86/topology: Create logical package id
Date: Sat, 7 May 2016 07:16:05 +0200 [thread overview]
Message-ID: <20160507051605.GA13962@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1605062046270.3540@nanos>
* Thomas Gleixner <tglx@linutronix.de> wrote:
> > I was hoping to get your feedback, since you are the patch author. Do
> > you think gathering any additional data will help diagnose this issue,
> > or would it be best to submit a revert request?
>
> Yuck. That dies with a divide error. And that looks like XEN is supplying crap
> data in the CPUID.
>
> Does the patch below cure the issue?
>
> Thanks,
>
> tglx
>
> 8<---------------
>
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -332,6 +332,11 @@ static void __init smp_init_package_map(
> * primary cores.
> */
> ncpus = boot_cpu_data.x86_max_cores;
> + if (!ncpus) {
> + pr_warn("x86_max_cores == zero !?!?");
> + ncpus = 1;
> + }
> +
Even if the underlying Xen bug is fixed, I think we should add this protective
measure to defend against future CPUID mishaps.
Thanks,
Ingo
next prev parent reply other threads:[~2016-05-07 5:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-06 18:15 [v4.6-rc1 Regression] x86/topology: Create logical package id Joseph Salisbury
2016-05-06 18:48 ` Thomas Gleixner
2016-05-06 19:13 ` Boris Ostrovsky
2016-05-06 19:38 ` Joseph Salisbury
2016-05-06 20:46 ` Boris Ostrovsky
2016-05-06 20:51 ` Joseph Salisbury
2016-05-06 21:24 ` Boris Ostrovsky
2016-05-06 19:38 ` Joseph Salisbury
2016-05-06 20:50 ` Joseph Salisbury
2016-05-07 5:16 ` Ingo Molnar [this message]
2016-05-07 8:12 ` [tip:x86/urgent] x86/topology: Handle CPUID bogosity gracefully tip-bot for Thomas Gleixner
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