Re: [Qemu-devel] 3.1: second invocation of migrate crashes qemu

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Kevin Wolf (kwolf@redhat.com) wrote:
> Am 14.01.2019 um 11:51 hat Dr. David Alan Gilbert geschrieben:
> > * Michael Tokarev (mjt@tls.msk.ru) wrote:
> > > $ qemu-system-x86_64 -monitor stdio -hda foo.img
> > > QEMU 3.1.0 monitor - type 'help' for more information
> > > (qemu) stop
> > > (qemu) migrate "exec:cat >/dev/null"
> > > (qemu) migrate "exec:cat >/dev/null"
> > > qemu-system-x86_64: /build/qemu/qemu-3.1/block.c:4647: bdrv_inactivate_recurse: Assertion `!(bs->open_flags & BDRV_O_INACTIVE)' failed.
> > > Aborted
> > 
> > And on head as well;  it only happens if the 1st migrate is succesful;
> > if it got cancelled the 2nd one works, so it's not too bad.
> > 
> > I suspect the problem here is all around locking/ownership - the block
> > devices get shutdown at the end of migration since the assumption is
> > that the other end has them open now and we had better release them.
> 
> Yes, only "cont" gets control back to the source VM.
> 
> I think we really should limit the possible monitor commands in the
> postmigrate status, and possibly provide a way to get back to the
> regular paused state (which means getting back control of the resources)
> without resuming the VM first.

This error is a little interesting if you'd done something like:


     src:
         stop
         migrate

     dst:
         <kill qemu for some reason>
         start a new qemu

     src:
         migrate

Now that used to work (safely) - note we've not started
a VM succesfully anywhere else.

Now the source refuses to let that happen - with a rather
nasty abort.

Dave

> Kevin
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK