Re: [virtio-comment] RE: VIRTIO_NET_F_MRG_RXBUF number of descriptors

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Jul 09, 2019 at 08:33:16AM +0000, Savir, Gil wrote:
> In addition I suggest, Section 5.1.6.4 (Processing of Incoming Packets) should be changed from:
> "
> 1. num_buffers indicates how many descriptors this packet is spread over (including this one): this will always be 1 if VIRTIO_NET_F_MRG_RXBUF was not negotiated. This allows receipt of large packets without having to allocate large buffers: a packet that does not fit in a single buffer can flow over to the next buffer, and so on. In this case, there will be at least num_buffers used buffers in the virtqueue, and the device chains them together to form a single packet in a way similar to how it would store it in a single buffer spread over multiple descriptors. The other buffers will not begin with a struct virtio_net_hdr.
> 2. If num_buffers is one, then the entire packet will be contained within this buffer, immediately following the struct virtio_net_hdr.
> "
> 
> to
> 
> "
> 1. num_buffers indicates how many descriptor-chains this packet is spread over (including this one): this will always be 1 if VIRTIO_NET_F_MRG_RXBUF was not negotiated. This allows receipt of large packets without having to allocate large buffers: a packet that does not fit in a single buffer can flow over to the next buffer, and so on. In this case, there will be at least num_buffers used buffers in the virtqueue, and the device merge them together to form a single packet. The other buffers will not begin with a struct virtio_net_hdr.
> 2. If num_buffers is one, then the entire packet will be contained within this descriptors-chain, immediately following the struct virtio_net_hdr.
> "
> 
> This, in order to prevent more confusion, caused by the use of the word "descriptor" interchanging as between descriptor and descriptor-chain.

Please change it to "used buffers" instead of "descriptor-chains" for
consistency with the rest of the specification.

Thanks,
Stefan

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