From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Lieven Subject: Re: [Qemu-devel] Help debugging a regression in KVM Module Date: Tue, 18 Aug 2015 16:54:28 +0200 Message-ID: <55D34724.6000209@kamp.de> References: <55CDCCE6.90102@kamp.de> <87zj1thc5z.fsf@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "qemu-devel@nongnu.org" , "kvm@vger.kernel.org" , Paolo Bonzini , rkrcmar@redhat.com, Jan Kiszka To: =?UTF-8?B?QWxleCBCZW5uw6ll?= Return-path: Received: from mx01.kamp.de ([82.141.2.16]:48416 "EHLO mx01.kamp.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751399AbbHROye (ORCPT ); Tue, 18 Aug 2015 10:54:34 -0400 In-Reply-To: <87zj1thc5z.fsf@linaro.org> Sender: kvm-owner@vger.kernel.org List-ID: Am 14.08.2015 um 22:01 schrieb Alex Benn=C3=A9e: > Peter Lieven writes: > >> Hi, >> >> some time a go I stumbled across a regression in the KVM Module that= has been introduced somewhere >> between 3.17 and 3.19. >> >> I have a rather old openSUSE guest with an XFS filesystem which real= iably crashes after some live migrations. >> I originally believed that the issue might be related to my setup wi= th a 3.12 host kernel and kvm-kmod 3.19, >> but I now found that it is also still present with a 3.19 host kerne= l with included 3.19 kvm module. >> >> My idea was to continue testing on a 3.12 host kernel and then bisec= t all commits to the kvm related parts. >> >> Now my question is how to best bisect only kvm related changes (thos= e >> that go into kvm-kmod)? > In general I don't bother. As it is a bisection you eliminate half th= e > commits at a time you get their fairly quickly anyway. However you ca= n > tell bisect which parts of the tree you car about: > > git bisect start -- arch/arm64/kvm include/linux/kvm* include/uapi= /linux/kvm* virt/kvm/ After some experiments I was able to find out the bad commit that intro= duced the regression: commit f30ebc312ca9def25650b4e1d01cdb425c310dca Author: Radim Kr=C4=8Dm=C3=A1=C5=99 Date: Thu Oct 30 15:06:47 2014 +0100 It seems that this optimisation is not working reliabliy after live mig= ration. I can't reproduce if I take a 3.19 kernel and revert this single commit. Peter