virtio — archive

[PATCH v6 0/5] packed ring layout spec

From: Michael S. Tsirkin <[email protected]>
To: [email protected]
Date: Wed, 10 Jan 2018 11:16:00 -0000

On Wed, Jan 10, 2018 at 12:14:03PM +0100, Cornelia Huck wrote: > On Wed, 10 Jan 2018 13:10:49 +0200 > "Michael S. Tsirkin" <[email protected]> wrote: > > > On Wed, Jan 10, 2018 at 11:33:15AM +0100, Cornelia Huck wrote: > > > On Wed, 10 Jan 2018 11:47:53 +0200 > > > "Michael S. Tsirkin" <[email protected]> wrote: > > > > > > > OK, this is in a shape where we could include it in the spec. > > > > Changes from v5: > > > > - scope reductions (see below). We can add more > > > > features down the road, hopefully reduced scope will be enough > > > > to finalize spec soon. > > > > - cleanup and integrate in the spec > > > > - pseudo-code > > > > > > > > Deferred features: > > > > - dropped _F_DESC_LIST, 1.0 includes this unconditionally, we > > > > can do same > > > > - dropped event structure change notifications - needed for > > > > efficient hardware implementations but let's add this on top > > > > > > > > 3 1st patches just move text around so all virtio 1.0 > > > > things are in the same place. 2 last ones add the new layout > > > > > > > > Option to mark descriptors as not generating events isn't > > > > yet implemented. Again, let's add this on top. > > > > > > > > I also note that for hardware implementations, a different > > > > set of memory barriers is needed. Again, let's add this on top > > > > > > > > not linking into conformance sections, will add after spec > > > > itself is approved. > > > > > > > > Michael S. Tsirkin (5): > > > > content: move 1.0 queue format out to a separate section > > > > content: move ring text out to a separate file > > > > content: move virtqueue operation description > > > > packed virtqueues: more efficient virtqueue layout > > > > packed-ring: add in order request support > > > > > > > > conformance.tex | 4 +- > > > > content.tex | 718 +++++ --------------------------------------------------- > > > > packed-ring.tex | 692 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > > split-ring.tex | 666 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > > 4 files changed, 1423 insertions(+), 657 deletions(-) > > > > create mode 100644 packed-ring.tex > > > > create mode 100644 split-ring.tex > > > > > > > > > > One thing I just noticed: This does not seem to contain any changes for > > > transports. For ccw, we use different payloads in the SET_VQ command > > > for legacy (pre-virtio-1) and virtio-1 split layout. I think we would > > > need a new SET_VQ payload for the packed ring guarded by a new > > > revision, but I have not investigated it yet. I have not yet thought > > > through how this interacts with feature negotiation, either. > > > > Good point. > > There's exactly same number of chunks (descriptor, device and driver > > event suppression). > > > > So the idea is to substitute descriptor for descriptor, device event > > suppression for available ring and driver event suppression for > > used ring. > > > > That's why we don't need to change transports. > > > > I will add text to clarify that. > > I think we also need to update the text for the transports, as they > explicitly refer to avail/used. Exactly. > > > > > Otherwise, I don't see any reason why the packed ring would not work > > > fine for ccw as well.