From mboxrd@z Thu Jan  1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 191481] New: Virtual machine CPU counters are broken forever
 after live migration to system with "steal time overflow" KVM bug
Date: Thu, 29 Dec 2016 16:21:38 +0000
Message-ID: <bug-191481-28872@https.bugzilla.kernel.org/>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
To: kvm@vger.kernel.org
Return-path: <kvm-owner@vger.kernel.org>
Received: from mail.kernel.org ([198.145.29.136]:59780 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1752901AbcL2QVp (ORCPT <rfc822;kvm@vger.kernel.org>);
        Thu, 29 Dec 2016 11:21:45 -0500
Received: from mail.kernel.org (localhost [127.0.0.1])
        by mail.kernel.org (Postfix) with ESMTP id 747EA2052A
        for <kvm@vger.kernel.org>; Thu, 29 Dec 2016 16:21:43 +0000 (UTC)
Received: from bugzilla1.web.kernel.org (bugzilla1.web.kernel.org [172.20.200.51])
        by mail.kernel.org (Postfix) with ESMTP id F3E3D2051D
        for <kvm@vger.kernel.org>; Thu, 29 Dec 2016 16:21:38 +0000 (UTC)
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

https://bugzilla.kernel.org/show_bug.cgi?id=191481

            Bug ID: 191481
           Summary: Virtual machine CPU counters are broken forever after
                    live migration to system with "steal time overflow"
                    KVM bug
           Product: Virtualization
           Version: unspecified
    Kernel Version: Found since 3.18.31, still resides in latest ubuntu
                    3.19..4.8 builds
          Hardware: Intel
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: ds@vo-ix.ru
        Regression: No

All (at least, compiled for ubuntu) kernels had the stolen time overflow bug,
described in links below:
http://lists.gnu.org/archive/html/qemu-devel/2015-06/msg01295.html
https://bugs.launchpad.net/linux/+bug/1494350

It was fixed (in ubuntu) on summer 2016, so till now still exists affected
hosts.

Kernels built before Apr 2016 bypass "%still" counter as is, so sar output
likes this:
11:11:15 AM     CPU     %user     %nice   %system   %iowait    %steal     %idle
11:10:48 AM     all      0.00      0.00      0.50      0.00      0.00     99.50
11:10:49 AM     all      0.00      0.00      0.00      0.00   
18823208238479134720.00    203.06
11:10:50 AM     all      0.00      0.00      0.00      0.00      0.00    100.00

While all newer kernel counters I've been tested sticks:
11:11:15 AM     CPU     %user     %nice   %system   %iowait    %steal     %idle
07:07:56 AM     all      0.50      0.00      0.00      0.00      0.00     99.50
07:07:57 AM     all      0.00      0.00      0.50      0.00      0.00     99.50
07:07:58 AM     all      0.00      0.00      0.50      0.00      0.00     99.50
07:07:59 AM     all      0.00      0.00      0.00      0.00    100.00      0.00
07:08:00 AM     all      0.00      0.00      0.00      0.00    100.00      0.00
07:08:01 AM     all      0.00      0.00      0.00      0.00    100.00      0.00

%steal is always 100% after migration.

I slightly suspect that the reason resides in commit
0185604c2d82c560dab2f2933a18f797e74ab5a8.

-- 
You are receiving this mail because:
You are watching the assignee of the bug.