[Xen-devel] [PATCH RFC 2/3] Virtio draft III: example net driver

[Rusty Russell <rusty@xxxxxxxxxxxxxxx>]

Net driver using virtio

TODO:
        1) GSO.
        2) Checksum options.
        3) Big packets.

Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
---
 drivers/net/Makefile       |    2 
 drivers/net/virtio_net.c   |  277 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/virtio_net.h |   12 +
 3 files changed, 290 insertions(+), 1 deletion(-)

===================================================================
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -37,7 +37,7 @@ obj-$(CONFIG_CASSINI) += cassini.o
 
 obj-$(CONFIG_MACE) += mace.o
 obj-$(CONFIG_BMAC) += bmac.o
-
+obj-y += virtio_net.o
 obj-$(CONFIG_DGRS) += dgrs.o
 obj-$(CONFIG_VORTEX) += 3c59x.o
 obj-$(CONFIG_TYPHOON) += typhoon.o
===================================================================
--- /dev/null
+++ b/drivers/net/virtio_net.c
@@ -0,0 +1,277 @@
+/* A simple network driver using virtio.
+ *
+ * Copyright 2007 Rusty Russell <rusty@xxxxxxxxxxxxxxx> IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+//#define DEBUG
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/module.h>
+#include <linux/virtio.h>
+#include <linux/scatterlist.h>
+
+/* FIXME: Make dynamic */
+#define MAX_PACKET_LEN (ETH_HLEN+ETH_DATA_LEN)
+
+#define SKB_ID(skb) (*(unsigned long *)(skb)->cb)
+
+struct virtnet_info
+{
+       struct virtio_device *vdev;
+       struct net_device *ndev;
+
+       /* Number of input buffers, and max we've ever had. */
+       unsigned int num, max;
+
+       /* Receive & send queues. */
+       struct sk_buff_head recv;
+       struct sk_buff_head send;
+};
+
+static bool skb_xmit_done(struct virtio_device *vdev)
+{
+       struct virtnet_info *vi = vdev->priv;
+
+       /* In case we were waiting for output buffers. */
+       netif_wake_queue(vi->ndev);
+       return true;
+}
+
+static void receive_skb(struct net_device *dev, struct sk_buff *skb,
+                       unsigned len)
+{
+       if (unlikely(len < ETH_HLEN)) {
+               pr_debug("%s: short packet %i\n", dev->name, len);
+               dev->stats.rx_length_errors++;
+               dev_kfree_skb(skb);
+               return;
+       }
+       BUG_ON(len > MAX_PACKET_LEN);
+
+       skb_trim(skb, len);
+       skb->protocol = eth_type_trans(skb, dev);
+       pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
+                ntohs(skb->protocol), skb->len, skb->pkt_type);
+       dev->stats.rx_bytes += skb->len;
+       dev->stats.rx_packets++;
+       netif_rx(skb);
+}
+
+static void try_fill_recv(struct virtnet_info *vi)
+{
+       struct sk_buff *skb;
+       struct scatterlist sg[MAX_SKB_FRAGS];
+       unsigned long sgnum, id;
+
+       for (;;) {
+               skb = netdev_alloc_skb(vi->ndev, MAX_PACKET_LEN);
+               if (unlikely(!skb))
+                       break;
+
+               skb_put(skb, MAX_PACKET_LEN);
+               sgnum = skb_to_sgvec(skb, sg, 0, skb->len);
+               skb_queue_head(&vi->recv, skb);
+
+               id = vi->vdev->ops->add_inbuf(vi->vdev, sg, sgnum, skb);
+               if (IS_ERR_VALUE(id)) {
+                       skb_unlink(skb, &vi->recv);
+                       kfree_skb(skb);
+                       break;
+               }
+               vi->num++;
+       }
+       if (unlikely(vi->num > vi->max))
+               vi->max = vi->num;
+       vi->vdev->ops->sync(vi->vdev, VIRTIO_IN);
+}
+
+static bool skb_recv_done(struct virtio_device *vdev)
+{
+       struct virtnet_info *vi = vdev->priv;
+
+       netif_rx_schedule(vi->ndev);
+       /* Suppress further interrupts. */
+       return false;
+}
+
+static int virtnet_poll(struct net_device *dev, int *budget)
+{
+       struct virtnet_info *vi = netdev_priv(dev);
+       struct sk_buff *skb = NULL;
+       unsigned int len, received = 0;
+
+again:
+       while (received < dev->quota &&
+              (skb = vi->vdev->ops->get_inbuf(vi->vdev, &len)) != NULL) {
+               __skb_unlink(skb, &vi->recv);
+               receive_skb(vi->ndev, skb, len);
+               vi->num--;
+               received++;
+       }
+
+        dev->quota -= received;
+        *budget -= received;
+
+       /* FIXME: If we oom and completely run out of inbufs, we need
+        * to start a timer trying to fill more. */
+       if (vi->num < vi->max / 2)
+               try_fill_recv(vi);
+
+       /* Still more work to do? */
+       if (skb)
+               return 1; /* not done */
+
+       netif_rx_complete(dev);
+       if (unlikely(!vi->vdev->ops->restart_in(vi->vdev))
+           && netif_rx_reschedule(dev, received))
+               goto again;
+
+       return 0;
+}
+
+static void free_old_xmit_skbs(struct virtnet_info *vi)
+{
+       struct sk_buff *skb;
+       unsigned int len;
+
+       while ((skb = vi->vdev->ops->get_outbuf(vi->vdev, &len)) != NULL) {
+               pr_debug("Sent skb %p\n", skb);
+               __skb_unlink(skb, &vi->send);
+               vi->ndev->stats.tx_bytes += len;
+               vi->ndev->stats.tx_packets++;
+               kfree_skb(skb);
+       }
+}
+
+static int start_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+       struct virtnet_info *vi = netdev_priv(dev);
+       unsigned long num, id;
+       struct scatterlist sg[MAX_SKB_FRAGS];
+       const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
+
+       pr_debug("%s: xmit %p %02x:%02x:%02x:%02x:%02x:%02x\n",
+                dev->name, skb,
+                dest[0], dest[1], dest[2], dest[3], dest[4], dest[5]);
+
+       free_old_xmit_skbs(vi);
+
+       num = skb_to_sgvec(skb, sg, 0, skb->len);
+       __skb_queue_head(&vi->send, skb);
+       id = vi->vdev->ops->add_outbuf(vi->vdev, sg, num, skb);
+       if (IS_ERR_VALUE(id)) {
+               pr_debug("%s: virtio not prepared to send\n", dev->name);
+               skb_unlink(skb, &vi->send);
+               netif_stop_queue(dev);
+               return NETDEV_TX_BUSY;
+       }
+       SKB_ID(skb) = id;
+       vi->vdev->ops->sync(vi->vdev, VIRTIO_OUT);
+
+       return 0;
+}
+
+static int virtnet_open(struct net_device *dev)
+{
+       struct virtnet_info *vi = netdev_priv(dev);
+
+       try_fill_recv(vi);
+
+       /* If we didn't even get one input buffer, we're useless. */
+       if (vi->num == 0)
+               return -ENOMEM;
+
+       return 0;
+}
+
+static int virtnet_close(struct net_device *dev)
+{
+       struct virtnet_info *vi = netdev_priv(dev);
+       struct sk_buff *skb;
+
+       /* networking core has neutered skb_xmit_done/skb_recv_done, so don't
+        * worry about races vs. get_buf(). */
+       while ((skb = __skb_dequeue(&vi->recv)) != NULL) {
+               vi->vdev->ops->detach_inbuf(vi->vdev, SKB_ID(skb));
+               kfree_skb(skb);
+               vi->num--;
+       }
+       while ((skb = __skb_dequeue(&vi->send)) != NULL) {
+               vi->vdev->ops->detach_outbuf(vi->vdev, SKB_ID(skb));
+               kfree_skb(skb);
+       }
+       BUG_ON(vi->num != 0);
+       return 0;
+}
+
+static struct virtio_driver_ops virtnet_ops = {
+       .in = skb_recv_done,
+       .out = skb_xmit_done,
+};
+
+struct net_device *virtnet_probe(struct virtio_device *vdev,
+                                const u8 mac[ETH_ALEN])
+{
+       int err;
+       struct net_device *dev;
+       struct virtnet_info *vi;
+
+       dev = alloc_etherdev(sizeof(struct virtnet_info));
+       if (!dev)
+               return ERR_PTR(-ENOMEM);
+
+       SET_MODULE_OWNER(dev);
+
+       ether_setup(dev);
+       memcpy(dev->dev_addr, mac, ETH_ALEN);
+       dev->open = virtnet_open;
+       dev->stop = virtnet_close;
+       dev->poll = virtnet_poll;
+       dev->hard_start_xmit = start_xmit;
+       dev->weight = 16;
+       SET_NETDEV_DEV(dev, vdev->dev);
+
+       vi = netdev_priv(dev);
+       vi->vdev = vdev;
+       vi->ndev = dev;
+       vdev->priv = vi;
+       vdev->driver_ops = &virtnet_ops;
+       skb_queue_head_init(&vi->recv);
+       skb_queue_head_init(&vi->send);
+
+       err = register_netdev(dev);
+       if (err) {
+               pr_debug("virtio_net: registering device failed\n");
+               goto free;
+       }
+       pr_debug("virtnet: registered device %s\n", dev->name);
+       return dev;
+
+free:
+       free_netdev(dev);
+       return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(virtnet_probe);
+
+void virtnet_remove(struct net_device *dev)
+{
+       unregister_netdev(dev);
+       free_netdev(dev);
+}
+EXPORT_SYMBOL_GPL(virtnet_remove);
+
+MODULE_DESCRIPTION("Virtio network driver");
+MODULE_LICENSE("GPL");
===================================================================
--- /dev/null
+++ b/include/linux/virtio_net.h
@@ -0,0 +1,12 @@
+#ifndef _LINUX_VIRTIO_NET_H
+#define _LINUX_VIRTIO_NET_H
+#include <linux/types.h>
+#include <linux/etherdevice.h>
+struct net_device;
+struct virtio_device;
+
+struct net_device *virtnet_probe(struct virtio_device *vdev,
+                                const u8 mac[ETH_ALEN]);
+void virtnet_remove(struct net_device *dev);
+
+#endif /* _LINUX_VIRTIO_NET_H */



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