[virtio-comment] Re: [PATCH v2 0/2] Add VIRTIO_RING_F_LARGE_INDIRECT_DESC

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

On Dienstag, 30. November 2021 13:06:31 CET Cornelia Huck wrote:
> On Mon, Nov 29 2021, Christian Schoenebeck <qemu_oss@crudebyte.com> wrote:
> > This is a follow-up of:
> > https://lists.oasis-open.org/archives/virtio-comment/202111/msg00059.html
> > 
> > These two patches introduce a more fine graded control over the maximum
> > length of an indirect descriptor table.
> > 
> > Associated Github Task:
> > https://github.com/oasis-tcs/virtio-spec/issues/122
> > 
> > v1 -> v2:
> >   * "active/pending message(s)" -> "vring slot(s)"
> >   
> >     NOTE: I decided to use the term "vring slot(s)" over the previously
> >     suggested term "buffer(s)" as I found tha latter too ambiguous in this
> >     context. [patch 1]
> >   
> >   * "... but does not oppose a limit to the actual bulk data size
> >   
> >     being transmitted."
> >     ->
> >     " ... but does not oppose a limit to the actual bulk data size
> >     being transmitted when indirect descriptors are used." [patch 1]
> >   
> >   * Add common configuration field "queue_indirect_size" and make it
> >   
> >     mandatory as of revision 3. [NEW patch 2]
> 
> Now you have me confused: 'revision' is a ccw transport concept, but you
> only add support on the pci transport? It's fine to leave out ccw (and
> mmio) for now, but you should not talk about revision 3...

Looks like I was too quick on this one. Right, the name virtio_pci_common_cfg 
should have suggested to me that this was PCI specific. :) I simply assumed 
this was a common config structure shared by all bus types.

And I had no idea that you were referring with "revision" to a bus specific 
mechanism either. I assumed virtio v1.0 = rev1, virtio v1.1 = rev2 and that 
the upcoming spec to become v1.2 = rev3 (i.e. for all bus tyes).

So what is the desired approach to proceed on this overall task, should this 
just be addressed on PCI for now as first step?

And what about the intended availability of this new virtio_pci_common_cfg 
field "queue_indirect_size", should it be optional per se, independent of the 
virtio version or rather a mandatory field in upcoming virtio version?

> > Christian Schoenebeck (2):
> >   Add VIRTIO_RING_F_LARGE_INDIRECT_DESC
> >   Add common configuration field "queue_indirect_size"
> >  
> >  content.tex    | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  split-ring.tex |  7 ++++++-
> >  2 files changed, 62 insertions(+), 1 deletion(-)