On Wed, Dec 06, 2017 at 09:30:27PM +0800, Ying Fang wrote: > > On 2017/12/1 22:39, Michael S. Tsirkin wrote: > > On Fri, Dec 01, 2017 at 01:58:32PM +0800, fangying wrote: > >> QEMU will abort when vhost-user process is restarted during migration > >> when vhost_log_global_start/stop is called. The reason is clear that > >> vhost_dev_set_log returns -1 because network connection is lost. > >> > >> To handle this situation, let's cancel migration by setting migrate > >> state to failure and report it to user. > > > > In fact I don't see this as the right way to fix it. Backend is dead so why > > not just proceed with migration? We just need to make sure we re-send > > migration data on re-connect. > > This is where vhost start/stop migration dirty log. The original code aborts > qemu here beacuse vhost data stream may break down if we fail to start/stop > vhost dirty log during migration. Backend may be active after > vhost_log_global_start. > > dirty log start ----------------- dirty log stop > ^ ^ > | | > ----- backend dead ----- backend active
I'm sorry, I don't understand yet. Backend is active after logging started - why is this a problem? > Currently we don't re-send migration data on re-connect in this situation. > May we should work it out. So basically backend connects after logging started, and we do not tell it to start logging and where - is that the issue? I agree, that would be a bug then. -- MST
