On 10.02.20 10:40, Eugenio Perez Martin wrote:

Hi Christian.

I'm not able to reproduce the failure with eccb852f1fe6bede630e2e4f1a121a81e34354ab commit. Could you add more data? Your configuration (libvirt or qemu line), and host's dmesg output if any?

I do the following in the guest:
ping -c 200 -f somevalidip; reboot
sometimes I need to do that multiple times and sometimes I do not get a guest crash but host dmesg like

Guest moved used index from 0 to 292

xml is pretty simple

    <interface type='direct'>
      <mac address='52:54:00:7c:2c:f3'/>
      <source dev='encbd00' mode='bridge'/>
      <model type='virtio'/>
      <driver name='vhost'/>
      <address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0001'/>
    </interface>


Reverting this patch seems to make both problems go away.

Thanks!

On Fri, Feb 7, 2020 at 9:13 AM Christian Borntraeger <borntraeger@de.ibm.com <mailto:borntraeger@de.ibm.com>> wrote:



    On 07.02.20 08:58, Michael S. Tsirkin wrote:
    > On Fri, Feb 07, 2020 at 08:47:14AM +0100, Christian Borntraeger wrote:
    >> Also adding Cornelia.
    >>
    >>
    >> On 06.02.20 23:17, Michael S. Tsirkin wrote:
    >>> On Thu, Feb 06, 2020 at 04:12:21PM +0100, Christian Borntraeger wrote:
    >>>>
    >>>>
    >>>> On 06.02.20 15:22, eperezma@redhat.com <mailto:eperezma@redhat.com> wrote:
    >>>>> Hi Christian.
    >>>>>
    >>>>> Could you try this patch on top of ("38ced0208491 vhost: use batched version by default")?
    >>>>>
    >>>>> It will not solve your first random crash but it should help with the lost of network connectivity.
    >>>>>
    >>>>> Please let me know how does it goes.
    >>>>
    >>>>
    >>>> 38ced0208491 + this seem to be ok.
    >>>>
    >>>> Not sure if you can make out anything of this (and the previous git bisect log)
    >>>
    >>> Yes it does - that this is just bad split-up of patches, and there's
    >>> still a real bug that caused worse crashes :)
    >>>
    >>> So I just pushed batch-v4.
    >>> I expect that will fail, and bisect to give us
    >>>     vhost: batching fetches
    >>> Can you try that please?
    >>>
    >>
    >> yes.
    >>
    >> eccb852f1fe6bede630e2e4f1a121a81e34354ab is the first bad commit
    >> commit eccb852f1fe6bede630e2e4f1a121a81e34354ab
    >> Author: Michael S. Tsirkin <mst@redhat.com <mailto:mst@redhat.com>>
    >> Date:   Mon Oct 7 06:11:18 2019 -0400
    >>
    >>     vhost: batching fetches
    >>     
    >>     With this patch applied, new and old code perform identically.
    >>     
    >>     Lots of extra optimizations are now possible, e.g.
    >>     we can fetch multiple heads with copy_from/to_user now.
    >>     We can get rid of maintaining the log array.  Etc etc.
    >>     
    >>     Signed-off-by: Michael S. Tsirkin <mst@redhat.com <mailto:mst@redhat.com>>
    >>
    >>  drivers/vhost/test.c  |  2 +-
    >>  drivers/vhost/vhost.c | 39 ++++++++++++++++++++++++++++++++++-----
    >>  drivers/vhost/vhost.h |  4 +++-
    >>  3 files changed, 38 insertions(+), 7 deletions(-)
    >>
    >
    >
    > And the symptom is still the same - random crashes
    > after a bit of traffic, right?

    random guest crashes after a reboot of the guests. As if vhost would still
    write into now stale buffers.