[dpdk-dev] [PATCH 4/5] virtio: use any layout on transmit

Xie, Huawei huawei.xie at intel.com
Mon Oct 19 18:28:30 CEST 2015


On 10/19/2015 1:16 PM, Stephen Hemminger wrote:
> Virtio supports a feature that allows sender to put transmit
> header prepended to data.  It requires that the mbuf be writeable, correct
> alignment, and the feature has been negotiatied.  If all this works out,
> then it will be the optimum way to transmit a single segment packet.
"When using legacy interfaces, transitional drivers which have not
negotiated VIRTIO_F_ANY_LAYOUT
MUST use a single descriptor for the struct virtio_net_hdr on both
transmit and receive, with the
network data in the following descriptors."

I think we shouldn't assume that virtio header descriptor uses a
separate descriptor. It could be with data. Virtio RX(and dpdk vhost)
actually is implemented like this before, i.e, i thought this should be
inherent but not a feature.
Is the current RX implementation wrong?
[...]


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