virtio — archive

[Stefan Hajnoczi]

On Sun, Mar 05, 2023 at 07:18:24PM -0500, Michael S. Tsirkin wrote: > 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? In general, no. The driver must wait for the write completion before submitting the read if it wants consistency. Stefan