Re: Random guest crashes since 5c34d002dcc7 ("virtio_pci: use shared interrupts for virtqueues")

[Richard W.M. Jones]

 On Thu, Mar 23, 2017 at 03:51:25PM +0100, Thorsten Leemhuis wrote:
> Hi Christoph! Hi Michael!
> 
> (Mail roughly based on text from
> https://bugzilla.kernel.org/show_bug.cgi?id=194911 )
> 
> I'm seeing random crashes during boot every few boot attempts when
> running Linux 4.11-rc/mainline in a Fedora 26 guest under a CentOS7 host
> (CPU: Intel(R) Pentium(R) CPU G3220) using KVM. Sometimes when the guest
> actually booted the network did not work. To get some impressions of the
> crashes I got see this gallery:
> https://plus.google.com/+ThorstenLeemhuis/posts/FjyyGjNtrrG
> 
> Richard W.M. Jones and Adam Williamson see the same problems. See above
> bug for details. It seems they ran into the problem in the past few
> days, so I assume it's still present in mainline (I'm travelling
> currently and haven't had time for proper tests since last last Friday
> (pre-rc3); but I thought it's time to get the problem to the lists).
> 
> Long story short: Richard and I did bisections and we both found that
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=07ec51480b5e
> ("virtio_pci: use shared interrupts for virtqueues") is the first bad
> commit. Any idea what might be wrong? Do you need more details from us
> to fix this?

Laura Abbott posted a kernel RPM which works for me.  She has had to
revert quite a number of commits, which are detailed in this comment:

  https://bugzilla.redhat.com/show_bug.cgi?id=1430297#c7

Her reverting patch is also attached.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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