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

Rusty Russell
2007-06-16T13:17:05Z

Net driver using virtio

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

Signed-off-by: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
---
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-8n+1lVoiYb80n/F98K4Iww@public.gmane.org> 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 */