Re: [PATCH 2/2] virtio: Keep notifications disabled during drain

[Fiona Ebner <f.ebner@proxmox.com>]

Am 24.01.24 um 18:38 schrieb Hanna Czenczek:
> During drain, we do not care about virtqueue notifications, which is why
> we remove the handlers on it.  When removing those handlers, whether vq
> notifications are enabled or not depends on whether we were in polling
> mode or not; if not, they are enabled (by default); if so, they have
> been disabled by the io_poll_start callback.
> 
> Because we do not care about those notifications after removing the
> handlers, this is fine.  However, we have to explicitly ensure they are
> enabled when re-attaching the handlers, so we will resume receiving
> notifications.  We do this in virtio_queue_aio_attach_host_notifier*().
> If such a function is called while we are in a polling section,
> attaching the notifiers will then invoke the io_poll_start callback,
> re-disabling notifications.
> 
> Because we will always miss virtqueue updates in the drained section, we
> also need to poll the virtqueue once after attaching the notifiers.
> 
> Buglink: https://issues.redhat.com/browse/RHEL-3934
> Signed-off-by: Hanna Czenczek <hreitz@redhat.com>

Tested-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Fiona Ebner <f.ebner@proxmox.com>