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Subject: Re: [virtio-comment] [PATCH V2 1/2] virtio: introduce virtqueue state as basic facility
On Wed, Mar 24, 2021 at 04:15:55PM +0800, Jason Wang wrote: > å 2021/3/23 äå6:27, Stefan Hajnoczi åé: > > On Mon, Mar 22, 2021 at 11:47:16AM +0800, Jason Wang wrote: > > > +The \field{used_wrap_counter} field is the wrap counter that is used > > > +by the device. > > > + > > > +The used state is unnecessary when VIRTIO_RING_F_PACKED is not > > > +negotiated. > > > + > > > +See also \ref{sec:Packed Virtqueues / Driver and Device Ring Wrap Counters}. > > > + > > > +\drivernormative{\subsection}{Virtqueue State}{Basic Facilities of a Virtio Device / Virtqueue State} > > > + > > > +If VIRTIO_F_QUEUE_STATE has been negotiated, a driver MUST set the > > > +state of each virtqueue after setting the FEATURE_OK status bit but > > > +before setting the DRIVER_OK status bit. > > > + > > > +If VIRTIO_F_QUEUE_STATE has been negotiated. a driver MUST reset the > > s/negotiated./negotiated,/ > > > > > +device before getting the virtqueue state. > > Interesting approach, but it makes sense that the device must be stopped > > before we mess with the queue state :). > > > > I wonder whether requiring the device to keep state across reset will > > cause issues in the future or for testing/fuzzing. > > > > Another approach would have been to add a new status register bit for > > pausing the device. That reminds me of vhost. > > > That's the way I did here: > https://lists.oasis-open.org/archives/virtio-comment/202012/msg00027.html That design seems less risky. I think modifying the semantics of device reset might end up being a problem. Defining an explicit paused state for saving/loading state seems cleaner. Why did you end up switching approaches? Stefan
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