From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1756659AbcKBWsQ (ORCPT <rfc822;w@1wt.eu>);
        Wed, 2 Nov 2016 18:48:16 -0400
Received: from mx0a-000f0801.pphosted.com ([67.231.144.122]:48613 "EHLO
        mx0a-000f0801.pphosted.com" rhost-flags-OK-OK-OK-OK)
        by vger.kernel.org with ESMTP id S1755768AbcKBWsP (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 2 Nov 2016 18:48:15 -0400
Subject: Re: [RFC PATCH] perf/x86/intel/rapl: avoid access unallocate memory
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>, <x86@kernel.org>
References: <20161102122557.qs4rl6mb7n7l7j7p@linutronix.de>
CC: <linux-kernel@vger.kernel.org>, "M. Vefa Bicakci" <m.v.b@runbox.com>
From: "Charles (Chas) Williams" <ciwillia@brocade.com>
Message-ID: <24e69019-60d0-29e7-e31f-c6f00f9ed98a@brocade.com>
Date: Wed, 2 Nov 2016 18:47:49 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Icedove/45.3.0
MIME-Version: 1.0
In-Reply-To: <20161102122557.qs4rl6mb7n7l7j7p@linutronix.de>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 7bit
X-ClientProxiedBy: hq1wp-excas14.corp.brocade.com (10.70.38.103) To
 BRMWP-EXMB12.corp.brocade.com (172.16.59.130)
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-11-02_07:,,
 signatures=0
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0
 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011
 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0
 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1611020407
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 11/02/2016 08:25 AM, Sebastian Andrzej Siewior wrote:
> I am not sure if this a race with the new hotplug code or something that was
> always there. Both (M. Vefa Bicakc and Charles) say that the box boots
> sometimes fine (without the patch).  smp_store_boot_cpu_info() should have run
> before the notofoert and thus should have set the info properly. However I got
> the following bootlog from Charles with this patch:

I don't this this is a race.  Here is some debugging from the two CPU VM
(2 sockets, 1 core per socket).  In identify_cpu() we have:

         /* The boot/hotplug time assigment got cleared, restore it */
         c->logical_proc_id = topology_phys_to_logical_pkg(c->phys_proc_id);

The values just after this:

	[    0.228306] identify_cpu: c ffff88023fd0a040  logical_proc_id 65535  c->phys_proc_id 2

So what's interesting here, is the phys_proc_id of 2 for CPU1:

         int topology_phys_to_logical_pkg(unsigned int phys_pkg)
         {
                 if (phys_pkg >= max_physical_pkg_id)
                         return -1;
                 return physical_to_logical_pkg[phys_pkg];
         }

And we happen to know the max_physical_pkg_id is 2 in this case.
So apparently, topology_phys_to_logical_pkg() returns -1 and it gets
assigned to the logical_proc_id.

I don't know why the CPU's phys_proc_id is 2.