On Fri, 23 Oct 2015 09:00:38 +0000
"Xie, Huawei" <huawei.xie at intel.com> wrote:
> >> Why use merge-able rx header here in the tx region?
> > If mergeable rx is negotiated then the header must be used for
> > both Tx and Rx. I chose to allocate the largest possible header
> > needed, rather than having to deal with variable size data structure.
> Our original code is also using merge-able header for TX descriptor if
> this negotiated.
> I checked the virtio spec, all of the merge-able header is about
> receiving buffers, which is expected. That is why i feel weird here.
> Maybe not a big deal?
Since num_buffers is only in merge-able header, the negotiation is implied
to be symmetric.
Reading 0.95 spec
Under "Packet Transmission"
3. If the driver negotatied the VIRTIO_NET_F_MGR_RXBUF feature
the num_buffers field is set to zero.
