Re: [PATCH v7] virtio_net: support split header

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Sep 02, 2022 at 04:58:16PM +0800, Heng Qi wrote:
> When VIRTIO_NET_F_SPLIT_TRANSPORT_HEADER is negotiated,
> the driver requires that the buffers submitted to receiveq
> MUST be composed of at least two descriptors,
> which means that each buffer the device gets is a descriptor chain,
> even if the device does not split the header for some packets.
> 
> To store packet in the descriptor chain without header splitting
> by the device, the device MUST start with the first descriptor of
> the descriptor chain to store the packet, and MUST NOT set the
> VIRTIO_NET_HDR_F_SPLIT_TRANSPORT_HEADER bit in \field{flags}.
> 
> Thanks.

Descriptor chains will hurt performance badly.
How about simply making this feature depend on mergeable buffers?
Then we have a separate buffer for the header and
this works cleanly.

-- 
MST