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

[Stephen Hemminger <stephen@networkplumber.org>]

On Mon, 19 Oct 2015 16:56:02 +0000
"Xie, Huawei" <huawei.xie@intel.com> wrote:

> On 10/20/2015 12:43 AM, Stephen Hemminger wrote:
> > On Mon, 19 Oct 2015 16:28:30 +0000
> > "Xie, Huawei" <huawei.xie@intel.com> wrote:
> >
> >> 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."
> > The code checks for the any layout feature, what is the problem?
> My reply is removed. I said virtio RX is already implemented using this
> feature by default without negotiation(at the time of implementation, no
> idea of this feature), is the RX implementation wrong?
> 

No receiver is fine, it is okay to handle it coming in as long
as it doesn't assume that is the only possible layout.