On Sun, Mar 05, 2023 at 07:03:02PM -0500, Stefan Hajnoczi wrote: > On Sun, Mar 05, 2023 at 04:38:59AM -0500, Michael S. Tsirkin wrote: > > On Fri, Mar 03, 2023 at 03:21:33PM -0500, Stefan Hajnoczi wrote: > > > What happens if a command takes 1 second to complete, is the device > > > allowed to process the next command from the virtqueue during this time, > > > possibly completing it before the first command? > > > > > > This requires additional clarification in the spec because "they are > > > processed by the device in the order in which they are queued" does not > > > explain whether commands block the virtqueue (in order completion) or > > > not (out of order completion). > > > > Oh I begin to see. Hmm how does e.g. virtio scsi handle this? > > virtio-scsi, virtio-blk, and NVMe requests may complete out of order. > Several may be processed by the device at the same time.
Let's say I submit a write followed by read - is read guaranteed to return an up to date info? > They rely on multi-queue for abort operations: > > In virtio-scsi the abort requests (VIRTIO_SCSI_T_TMF_ABORT_TASK) are > sent on the control virtqueue. The the request identifier namespace is > shared across all virtqueues so it's possible to abort a request that > was submitted to any command virtqueue. > > NVMe also follows the same design where abort commands are sent on the > Admin Submission Queue instead of an I/O Submission Queue. It's possible > to identify NVMe requests by <Submission Queue ID, Command Identifier>. > > virtio-blk doesn't support aborting requests. > > I think the logic behind this design is that if a queue gets stuck > processing long-running requests, then the device should not be forced > to perform lookahead in the queue to find abort commands. A separate > control/admin queue is used for the abort requests. > > Stefan --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org
