On Tue, Aug 2, 2016 at 2:11 AM, Michael S. Tsirkin <m...@redhat.com> wrote: > On Mon, Aug 01, 2016 at 11:59:31PM +0000, Li, Liang Z wrote: >> > On Wed, Jul 06, 2016 at 12:49:06PM +0000, Li, Liang Z wrote: >> > > > > > > After live migration, 'guest-stats' can't get the expected >> > > > > > > memory status in the guest. This issue is caused by commit >> > 4eae2a657d. >> > > > > > > The value of 's->stats_vq_elem' will be NULL after live >> > > > > > > migration, and the check in the function >> > > > > > > 'balloon_stats_poll_cb()' will prevent the 'virtio_notify()' >> > > > > > > from executing. So guest will not update the memory status. >> > > > > > > >> > > > > > > Commit 4eae2a657d is doing the right thing, but >> > > > > > > 's->stats_vq_elem' >> > > > > > > should be treated as part of balloon device state and migrated >> > > > > > > to destination if it's not NULL to make everything works well. >> > > > > > > >> > > > > > > Signed-off-by: Liang Li <liang.z...@intel.com> >> > > > > > > Suggested-by: Paolo Bonzini <pbonz...@redhat.com> >> > > > > > > Cc: Michael S. Tsirkin <m...@redhat.com> >> > > > > > > Cc: Ladi Prosek <lpro...@redhat.com> >> > > > > > > Cc: Paolo Bonzini <pbonz...@redhat.com> >> > > > > > >> > > > > > I agree there's an issue but we don't change versions anymore. >> > > > > > Breaking migrations for everyone is also not nice. >> > > > > > >> > > > > > How about queueing virtio_balloon_receive_stats so it will get >> > > > > > invoked when vm starts? >> > > > > > >> > > > > >> > > > > Could you give more explanation about how it works? I can't catch >> > > > > you. >> > > > > >> > > > > Thanks! >> > > > > Liang >> > > > >> > > > virtqueue_discard before migration >> > > > >> > > > virtio_balloon_receive_stats after migration >> > > > >> > > >> > > Sorry, I still can't catch you. Maybe it's easier for you to submit a >> > > patch than writing a lot a words to make me understand your idea. >> > >> > I'm rather busy now. I might look into it towards end of the month. >> > >> > > I just don't understand why not to use the version to make things >> > > easier, is that not the original intent of version id? >> > >> > This was the original idea but we stopped using version ids since they have >> > many shortcomings. >> > >> > > If we want to extend the device and more states are needed, the idea >> > > you suggest can be used as a common solution? >> > > >> > > Thanks! >> > > Liang >> > >> > The idea is to try to avoid adding more state. that's not always possible >> > but in >> > this case element was seen but not consumed yet, so it should be possible >> > for destination to simply get it from the VQ again. >> > >> > > > -- >> > > > MST >> >> Hi Michel, >> >> Do you have time for this issue recently? >> >> Thanks! >> Liang
Hi Liang, I should be able to look into it this week if you help me with testing. Thanks, Ladi > Sorry, doesn't look like I will. > Idea is to make sure balloon_stats_poll_cb runs > on source. This will set stats_vq_elem to NULL. > > > -- > MST
