Re: [Qemu-devel] QMP events and the migration of halted machines

[John Snow <jsnow@redhat.com>]

On 02/24/2015 11:31 AM, John Snow wrote:
> In writing migration tests for qtest and ahci-test, I ran into an
> interesting pattern and wanted to know if this was expected:
>
> 1) Using blkdebug, I inject an error to execute once for the first flush
> request.
> 2) Executing the command, I get a STOP event.
> 3) I migrate the VM, and poll the source until it reports that it is
> completed.
>
> So far, so good.
>
> 4) I receive a RESUME event from the destination, even though the
> machine wasn't started.

Small correction: BLOCK_IO_ERROR and STOP occur here.

> 5) Naively, my script assumes the machine is stopped and sends
> {"execute": "cont"} to resume execution from the failed flush command.
> 6) I then see BLOCK_IO_ERROR, STOP, and then RESUME events in order.

...and not here.

> 7) The command appears to then execute and finish successfully.
>
> Is this the expected flow? I perhaps naively assumed that the machine
> would stay stopped during migration and wait for me to resume it, and
> not what appears to happen, which is resume automatically and then stop.
>
> This flow seems *very* odd to me.
>