Re: [PATCH 4/6] virtio network driver for QEMU (v2)

[Dor Laor <dor.laor-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Anthony Liguori wrote:
> This patch implements a very naive virtio network device backend in QEMU.
> Even with this simple implementation, it get's about 3x the throughput of
> rtl8139.  Of course, there's a whole lot of room for optimization to eliminate
> the unnecessary copying and support more advanced features.
>
> To use a virtio network device, simply specific '-net nic,model=virtio'
>
> Signed-off-by: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
>   
[snip]

> +/* TX */
> +static void virtio_net_handle_tx(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    VirtIONet *n = to_virtio_net(vdev);
> +    VirtQueueElement elem;
> +
> +    while (virtqueue_pop(vq, &elem)) {
> +	int i;
> +	size_t len = 0;
> +
> +	/* ignore the header for now */
> +	for (i = 1; i < elem.out_num; i++) {
> +	    qemu_send_packet(n->vc, elem.out_sg[i].iov_base,
> +			     elem.out_sg[i].iov_len);
> +	    len += elem.out_sg[i].iov_len;
> +	}
> +
> +	virtqueue_push(vq, &elem, sizeof(struct virtio_net_hdr) + len);
> +	virtio_notify(&n->vdev, vq);
> +    }
> +}
>   
Get the notify out of the while please.

Regardless of above, at the moment you copy the receive packets into 
virtio sg's.
I had a did an incomplete job of adding vectored read to qemu.
What's your opinion about it? Maybe using qemu's pending dma functions?
Regards & cheers,
Dor.
> +
> +VirtIODevice *virtio_net_init(PCIBus *bus, uint16_t vendor, uint16_t device,
> +			      NICInfo *nd, int devfn)
> +{
> +    VirtIONet *n;
> +
> +    n = (VirtIONet *)virtio_init_pci(bus, "virtio-net", vendor, device,
> +				     vendor, VIRTIO_ID_NET,
> +				     6, sizeof(VirtIONet));
> +
> +    n->vdev.update_config = virtio_net_update_config;
> +    n->vdev.get_features = virtio_net_get_features;
> +    n->rx_vq = virtio_add_queue(&n->vdev, virtio_net_handle_rx);
> +    n->tx_vq = virtio_add_queue(&n->vdev, virtio_net_handle_tx);
> +    n->can_receive = 0;
> +    memcpy(n->mac, nd->macaddr, 6);
> +    n->vc = qemu_new_vlan_client(nd->vlan, virtio_net_receive,
> +				 virtio_net_can_receive, n);
> +
> +    return &n->vdev;
> +}
> diff --git a/qemu/vl.h b/qemu/vl.h
> index 7b5cc8d..4f26fbb 100644
> --- a/qemu/vl.h
> +++ b/qemu/vl.h
> @@ -1401,6 +1401,9 @@ VirtIODevice *virtio_blk_init(PCIBus *bus, uint16_t vendor, uint16_t device,
>  
>  VirtIODevice *virtio_9p_init(PCIBus *bus, uint16_t vendor, uint16_t device);
>  
> +VirtIODevice *virtio_net_init(PCIBus *bus, uint16_t vendor, uint16_t device,
> +			      NICInfo *nd, int devfn);
> +
>  /* buf = NULL means polling */
>  typedef int ADBDeviceRequest(ADBDevice *d, uint8_t *buf_out,
>                                const uint8_t *buf, int len);
>
>   


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