On Wed, Apr 22, 2026 at 1:32 AM Stefano Garzarella <[email protected]> wrote: > > On Wed, 22 Apr 2026 at 03:16, Jorge Moreira <[email protected]> wrote: > > > > On Tue, Apr 21, 2026 at 2:12 PM Stefan Hajnoczi <[email protected]> wrote: > > > > > > On Mon, Apr 20, 2026 at 05:48:13PM -0700, Jorge Moreira wrote: > > > > While starting the vrings on SET_VRING_KICK could solve the state > > > > machine issue, it still won't notify the back-end that buffers are > > > > ready (the driver won't do this). Non-polling back-ends depend on this > > > > kick, especially for queues where data flows only from the driver to > > > > the back-end. Most implementations likely attempt to read from the > > > > queue only after receiving the kick. > > > > > > This is an interesting question to clarify in the spec. > > Yep, which is in part related to what I wrote in the other reply: > "I think the main issue to clarify is what the device should do > when the vrings are configured, but the driver has already been > initialized (which is usually the case after migration)." > > > > > > > Stefan > > > > This is the question that interests me most, to be honest. I'd rather > > have the discussion about when to activate the vrings in a different > > thread and keep this one focused on whether the front-end should send > > the kick or if the back-end is expected to check if there are "new" > > buffers in the vring after restore. > > > > IMO we don't need anything from the VMM. When the device receives > SET_VRING_KICK, it can check if the vring already contains buffers > (and this is the part we might need to clarify) and wake-up the other > threads (or always wake-ups them, as crosvm does IIUC, and let them > perform this check). > After sending the SET_VRING_KICK message to the device, the VMM has > the exact same knowledge of the vring state as the device, therefore, > it's still unclear to me why we need to inject that kick. > > Stefano >
Is it possible to activate a vring after it has been deactivated with VHOST_USER_GET_VRING_BASE? If yes, does the front-end need to send the kick file descriptor again with VHOST_USER_SET_VRING_KICK to reactivate it?
