Re: [virtio] Re: [PATCH v10 04/10] admin: introduce virtio admin virtqueues

[Stefan Hajnoczi <stefanha@redhat.com>]

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

Attachment: signature.asc
Description: PGP signature