[Qemu-devel] qemu virtio_net abort bisect

[Qemu-devel] qemu virtio_net abort bisect

[John Fastabend]

Hi Michael,

I'm getting a qemu crash from a load/unload of virtio_net.ko in guest
kernel with the following,

> ./x86_64-softmmu/qemu-system-x86_64 -hda /var/lib/libvirt/images/Fedora-test0.img \
       -m 4096 -enable-kvm -smp 4 -netdev tap,id=hn0,queues=4,vhost=on \
       -device virtio-net-pci,netdev=hn0,mq=on,vectors=9

in the host I do a simple

# rmmod virtio_net
# modprobe virtio_net

And bisecting points at this merge which just from the commit message
looks like it could be the culprit,

> Merge: 4eb28ab 5300063
> Author: Stefan Hajnoczi <stefanha@redhat.com>
> Date: Thu Nov 3 14:41:53 2016 +0000
> 
> Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into staging
> 
> virtio, pc: fixes and features
> 
> nvdimm hotplug support
> virtio migration and ioeventfd rework    <--- ioeventfd bits?
> virtio crypto device
> ipmi fixes
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Running without the above and everything works no issues. I started to
debug but admittedly got a bit lost in the notifier hooks maybe someone
will have a better idea. Here is the error I get,

> kvm_io_ioeventfd_add: error adding ioeventfd: File exists
> Aborted (core dumped)

I had a gdb backtrace at one point and can post that if its helpful.

Thanks,
John

Re: [Qemu-devel] qemu virtio_net abort bisect

[Michael S. Tsirkin]

On Thu, Nov 10, 2016 at 03:02:43PM -0800, John Fastabend wrote:
> Hi Michael,
> 
> I'm getting a qemu crash from a load/unload of virtio_net.ko in guest
> kernel with the following,
> 
> > ./x86_64-softmmu/qemu-system-x86_64 -hda /var/lib/libvirt/images/Fedora-test0.img \
>        -m 4096 -enable-kvm -smp 4 -netdev tap,id=hn0,queues=4,vhost=on \
>        -device virtio-net-pci,netdev=hn0,mq=on,vectors=9
> 
> in the host I do a simple
> 
> # rmmod virtio_net
> # modprobe virtio_net
> 
> And bisecting points at this merge which just from the commit message
> looks like it could be the culprit,
> 
> > Merge: 4eb28ab 5300063
> > Author: Stefan Hajnoczi <stefanha@redhat.com>
> > Date: Thu Nov 3 14:41:53 2016 +0000
> > 
> > Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into staging
> > 
> > virtio, pc: fixes and features
> > 
> > nvdimm hotplug support
> > virtio migration and ioeventfd rework    <--- ioeventfd bits?
> > virtio crypto device
> > ipmi fixes
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> Running without the above and everything works no issues. I started to
> debug but admittedly got a bit lost in the notifier hooks maybe someone
> will have a better idea. Here is the error I get,
> 
> > kvm_io_ioeventfd_add: error adding ioeventfd: File exists
> > Aborted (core dumped)
> 
> I had a gdb backtrace at one point and can post that if its helpful.
> 
> Thanks,
> John

Thanks!
Unfortunately it looks like a recent change broke this for a lot of people.
If you have the time, it might be helpful to try both

[PATCH] vhost-scsi: Update 'ioeventfd_started' with host notifiers
and
[PATCH v2] vhost: Update 'ioeventfd_started' with host notifiers



-- 
MST