Re: [PATCH] libxl: wait for QEMU exit before restarting a domain

[Jiaqing Zhao <Zhao.Jiaqing@amd.com>]

On 2026-11-05 16:13, Jan Beulich wrote:
> On 04.11.2026 18:33, Jason Andryuk wrote:
>> On 2026-11-04 01:46, Jiaqing Zhao wrote:
>>> The PID-based device model destruction path returns immediately after
>>> sending SIGHUP, before QEMU has necessarily exited. When an HVM guest
>>> reboots with VNC enabled, the new QEMU process may fail to bind the VNC
>>> port because the old process still holds it.
>>>
>>> Wait for QEMU to exit in a child process after singaling it for at most
>>
>> "signaling"
>>
>>> 60 seconds. If waiting fails or times out, log the error and retain the
>>> existing domain destruction behaviour.
>>
>> 60 seconds seems like a lot.  Did you measure the time to see how long 
>> it takes?  It's an upper bound, but maybe 10 seconds would be better?
> 
> Is 10s enough for it to time out upon disconnecting pass-through devices?
> I'm seeing this happen routinely, albeit with an older version of qemu.
> 
> Jan

I checked the code, passthorugh devices are removed via QMP, with
pci_remove_qmp_query_cb(), before sending SIGHUP to terminate QEMU.

Passing through a PCI SD card controller on my system took ~1.2s from
`xl destory` to sending SIGHUP to QEMU, and QEMU then took ~50ms to exit.
So 10s is pretty enough here I think.