On 14/02/2025 15:19, Daniel P. Berrangé wrote:
On Fri, Feb 14, 2025 at 01:59:20PM +0000, Daniel P. Berrangé wrote:
On Fri, Feb 14, 2025 at 11:18:55AM +0100, Laurent Vivier wrote:
On 14/02/2025 11:06, Markus Armbruster wrote:
Laurent Vivier <lviv...@redhat.com> writes:
The netdev reports NETDEV_VHOST_USER_CONNECTED event when
the chardev is connected, and NETDEV_VHOST_USER_DISCONNECTED
when it is disconnected.
The NETDEV_VHOST_USER_CONNECTED event includes the ChardevInfo
(label, filename and frontend_open).
This allows a system manager like libvirt to detect when the server
fails.
For instance with passt:
{ 'execute': 'qmp_capabilities' }
{ "return": { } }
[killing passt here]
{ "timestamp": { "seconds": 1739517243, "microseconds": 115081 },
"event": "NETDEV_VHOST_USER_DISCONNECTED",
"data": { "netdev-id": "netdev0" } }
[automatic reconnection with reconnect-ms]
{ "timestamp": { "seconds": 1739517290, "microseconds": 343777 },
"event": "NETDEV_VHOST_USER_CONNECTED",
"data": { "netdev-id": "netdev0",
"info": { "frontend-open": true,
"filename": "unix:",
"label": "chr0" } } }
Signed-off-by: Laurent Vivier <lviv...@redhat.com>
Standard question for events: if a management application misses an
event, say because it restarts and reconnects, is there a way to obtain
the missed information with a query command?
query-chardev could help but it doesn't provide the netdev id.
It doesn't have to IMHO. The application that created the NIC should know
what ID it assigned to both the netdev and chardev, and thus should be
able to use query-chardev to identify the chardev it previously
associated with the netdev.
That said I kind of wonder whether we should be adding events against
the chardev directly, instead of against the netdev use of chardev.
I don't know that is the best from a libvirt point of view.
ie CHARDEV_OPENED / CHARDEV_CLOSED events. For OPENED it is trivially
equivalent. For CLOSED it is a little trickier, since this patch does
delayed event dispatch from a bottom-half. If the chardev code was
able to emit this event from a bottom half itself, that could be OK
though.
Do we really need to delay the event?
libvirt could check the chardev user is really down before restarting it?
Without bh it's very simple:
@@ -68,9 +69,11 @@ void qemu_chr_be_event(Chardev *s, QEMUChrEvent event)
switch (event) {
case CHR_EVENT_OPENED:
s->be_open = 1;
+ qapi_event_send_chardev_connected(s->label);
break;
case CHR_EVENT_CLOSED:
s->be_open = 0;
+ qapi_event_send_chardev_disconnected(s->label);
break;
case CHR_EVENT_BREAK:
case CHR_EVENT_MUX_IN:
Thanks,
Laurent
With regards,
Daniel
