Am 14.08.2015 um 22:01 schrieb Alex Bennée:
Peter Lieven <p...@kamp.de> 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 realiably 
crashes after some live migrations.
I originally believed that the issue might be related to my setup with 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 kernel with 
included 3.19 kvm module.

My idea was to continue testing on a 3.12 host kernel and then bisect all 
commits to the kvm related parts.

Now my question is how to best bisect only kvm related changes (those
that go into kvm-kmod)?
In general I don't bother. As it is a bisection you eliminate half the
commits at a time you get their fairly quickly anyway. However you can
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 introduced 
the regression:

commit f30ebc312ca9def25650b4e1d01cdb425c310dca
Author: Radim Krčmář <rkrc...@redhat.com>
Date:   Thu Oct 30 15:06:47 2014 +0100

It seems that this optimisation is not working reliabliy after live migration. 
I can't reproduce if
I take a 3.19 kernel and revert this single commit.

Peter

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