Net driver using virtio

The network driver uses two virtqueues: one for input packets and one
for output packets.  This has nice locking properties (ie. we don't do
any for recv vs send).

TODO:
	1) Big packets.
	2) Multi-client devices (maybe separate driver?).
	3) Resolve freeing of old xmit skbs (Christian Borntraeger)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: netdev@vger.kernel.org

1 files changed, 435 insertions, 0 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
new file mode 100644
index 000000000000..e396c9d2af8d
--- /dev/null
+++ b/drivers/net/virtio_net.c
@@ -0,0 +1,435 @@
+/* A simple network driver using virtio.
+ *
+ * Copyright 2007 Rusty Russell <rusty@rustcorp.com.au> 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/virtio_net.h>
+#include <linux/scatterlist.h>
+
+/* FIXME: MTU in config. */
+#define MAX_PACKET_LEN (ETH_HLEN+ETH_DATA_LEN)
+
+struct virtnet_info
+{
+        struct virtio_device *vdev;
+        struct virtqueue *rvq, *svq;
+        struct net_device *dev;
+        struct napi_struct napi;
+
+        /* 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 inline struct virtio_net_hdr *skb_vnet_hdr(struct sk_buff *skb)
+{
+        return (struct virtio_net_hdr *)skb->cb;
+}
+
+static inline void vnet_hdr_to_sg(struct scatterlist *sg, struct sk_buff *skb)
+{
+        sg_init_one(sg, skb_vnet_hdr(skb), sizeof(struct virtio_net_hdr));
+}
+
+static bool skb_xmit_done(struct virtqueue *rvq)
+{
+        struct virtnet_info *vi = rvq->vdev->priv;
+
+        /* In case we were waiting for output buffers. */
+        netif_wake_queue(vi->dev);
+        return true;
+}
+
+static void receive_skb(struct net_device *dev, struct sk_buff *skb,
+                        unsigned len)
+{
+        struct virtio_net_hdr *hdr = skb_vnet_hdr(skb);
+
+        if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
+                pr_debug("%s: short packet %i\n", dev->name, len);
+                dev->stats.rx_length_errors++;
+                goto drop;
+        }
+        len -= sizeof(struct virtio_net_hdr);
+        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++;
+
+        if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
+                pr_debug("Needs csum!\n");
+                skb->ip_summed = CHECKSUM_PARTIAL;
+                skb->csum_start = hdr->csum_start;
+                skb->csum_offset = hdr->csum_offset;
+                if (skb->csum_start > skb->len - 2
+                    || skb->csum_offset > skb->len - 2) {
+                        if (net_ratelimit())
+                                printk(KERN_WARNING "%s: csum=%u/%u len=%u\n",
+                                       dev->name, skb->csum_start,
+                                       skb->csum_offset, skb->len);
+                        goto frame_err;
+                }
+        }
+
+        if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
+                pr_debug("GSO!\n");
+                switch (hdr->gso_type) {
+                case VIRTIO_NET_HDR_GSO_TCPV4:
+                        skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
+                        break;
+                case VIRTIO_NET_HDR_GSO_TCPV4_ECN:
+                        skb_shinfo(skb)->gso_type = SKB_GSO_TCP_ECN;
+                        break;
+                case VIRTIO_NET_HDR_GSO_UDP:
+                        skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+                        break;
+                case VIRTIO_NET_HDR_GSO_TCPV6:
+                        skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
+                        break;
+                default:
+                        if (net_ratelimit())
+                                printk(KERN_WARNING "%s: bad gso type %u.\n",
+                                       dev->name, hdr->gso_type);
+                        goto frame_err;
+                }
+
+                skb_shinfo(skb)->gso_size = hdr->gso_size;
+                if (skb_shinfo(skb)->gso_size == 0) {
+                        if (net_ratelimit())
+                                printk(KERN_WARNING "%s: zero gso size.\n",
+                                       dev->name);
+                        goto frame_err;
+                }
+
+                /* Header must be checked, and gso_segs computed. */
+                skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
+                skb_shinfo(skb)->gso_segs = 0;
+        }
+
+        netif_receive_skb(skb);
+        return;
+
+frame_err:
+        dev->stats.rx_frame_errors++;
+drop:
+        dev_kfree_skb(skb);
+}
+
+static void try_fill_recv(struct virtnet_info *vi)
+{
+        struct sk_buff *skb;
+        struct scatterlist sg[1+MAX_SKB_FRAGS];
+        int num, err;
+
+        for (;;) {
+                skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN);
+                if (unlikely(!skb))
+                        break;
+
+                skb_put(skb, MAX_PACKET_LEN);
+                vnet_hdr_to_sg(sg, skb);
+                num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
+                skb_queue_head(&vi->recv, skb);
+
+                err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb);
+                if (err) {
+                        skb_unlink(skb, &vi->recv);
+                        kfree_skb(skb);
+                        break;
+                }
+                vi->num++;
+        }
+        if (unlikely(vi->num > vi->max))
+                vi->max = vi->num;
+        vi->rvq->vq_ops->kick(vi->rvq);
+}
+
+static bool skb_recv_done(struct virtqueue *rvq)
+{
+        struct virtnet_info *vi = rvq->vdev->priv;
+        netif_rx_schedule(vi->dev, &vi->napi);
+        /* Suppress further interrupts. */
+        return false;
+}
+
+static int virtnet_poll(struct napi_struct *napi, int budget)
+{
+        struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi);
+        struct sk_buff *skb = NULL;
+        unsigned int len, received = 0;
+
+again:
+        while (received < budget &&
+               (skb = vi->rvq->vq_ops->get_buf(vi->rvq, &len)) != NULL) {
+                __skb_unlink(skb, &vi->recv);
+                receive_skb(vi->dev, skb, len);
+                vi->num--;
+                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);
+
+        /* All done? */
+        if (!skb) {
+                netif_rx_complete(vi->dev, napi);
+                if (unlikely(!vi->rvq->vq_ops->restart(vi->rvq))
+                    && netif_rx_reschedule(vi->dev, napi))
+                        goto again;
+        }
+
+        return received;
+}
+
+static void free_old_xmit_skbs(struct virtnet_info *vi)
+{
+        struct sk_buff *skb;
+        unsigned int len;
+
+        while ((skb = vi->svq->vq_ops->get_buf(vi->svq, &len)) != NULL) {
+                pr_debug("Sent skb %p\n", skb);
+                __skb_unlink(skb, &vi->send);
+                vi->dev->stats.tx_bytes += len;
+                vi->dev->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);
+        int num, err;
+        struct scatterlist sg[1+MAX_SKB_FRAGS];
+        struct virtio_net_hdr *hdr;
+        const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
+        DECLARE_MAC_BUF(mac);
+
+        pr_debug("%s: xmit %p %s\n", dev->name, skb, print_mac(mac, dest));
+
+        free_old_xmit_skbs(vi);
+
+        /* Encode metadata header at front. */
+        hdr = skb_vnet_hdr(skb);
+        if (skb->ip_summed == CHECKSUM_PARTIAL) {
+                hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+                hdr->csum_start = skb->csum_start - skb_headroom(skb);
+                hdr->csum_offset = skb->csum_offset;
+        } else {
+                hdr->flags = 0;
+                hdr->csum_offset = hdr->csum_start = 0;
+        }
+
+        if (skb_is_gso(skb)) {
+                hdr->gso_size = skb_shinfo(skb)->gso_size;
+                if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_ECN)
+                        hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4_ECN;
+                else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+                        hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
+                else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+                        hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+                else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
+                        hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
+                else
+                        BUG();
+        } else {
+                hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
+                hdr->gso_size = 0;
+        }
+
+        vnet_hdr_to_sg(sg, skb);
+        num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
+        __skb_queue_head(&vi->send, skb);
+        err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
+        if (err) {
+                pr_debug("%s: virtio not prepared to send\n", dev->name);
+                skb_unlink(skb, &vi->send);
+                netif_stop_queue(dev);
+                return NETDEV_TX_BUSY;
+        }
+        vi->svq->vq_ops->kick(vi->svq);
+
+        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;
+
+        napi_enable(&vi->napi);
+        return 0;
+}
+
+static int virtnet_close(struct net_device *dev)
+{
+        struct virtnet_info *vi = netdev_priv(dev);
+        struct sk_buff *skb;
+
+        napi_disable(&vi->napi);
+
+        /* networking core has neutered skb_xmit_done/skb_recv_done, so don't
+         * worry about races vs. get(). */
+        vi->rvq->vq_ops->shutdown(vi->rvq);
+        while ((skb = __skb_dequeue(&vi->recv)) != NULL) {
+                kfree_skb(skb);
+                vi->num--;
+        }
+        vi->svq->vq_ops->shutdown(vi->svq);
+        while ((skb = __skb_dequeue(&vi->send)) != NULL)
+                kfree_skb(skb);
+
+        BUG_ON(vi->num != 0);
+        return 0;
+}
+
+static int virtnet_probe(struct virtio_device *vdev)
+{
+        int err;
+        unsigned int len;
+        struct net_device *dev;
+        struct virtnet_info *vi;
+        void *token;
+
+        /* Allocate ourselves a network device with room for our info */
+        dev = alloc_etherdev(sizeof(struct virtnet_info));
+        if (!dev)
+                return -ENOMEM;
+
+        /* Set up network device as normal. */
+        ether_setup(dev);
+        dev->open = virtnet_open;
+        dev->stop = virtnet_close;
+        dev->hard_start_xmit = start_xmit;
+        dev->features = NETIF_F_HIGHDMA;
+        SET_NETDEV_DEV(dev, &vdev->dev);
+
+        /* Do we support "hardware" checksums? */
+        token = vdev->config->find(vdev, VIRTIO_CONFIG_NET_F, &len);
+        if (virtio_use_bit(vdev, token, len, VIRTIO_NET_F_NO_CSUM)) {
+                /* This opens up the world of extra features. */
+                dev->features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;
+                if (virtio_use_bit(vdev, token, len, VIRTIO_NET_F_TSO4))
+                        dev->features |= NETIF_F_TSO;
+                if (virtio_use_bit(vdev, token, len, VIRTIO_NET_F_UFO))
+                        dev->features |= NETIF_F_UFO;
+                if (virtio_use_bit(vdev, token, len, VIRTIO_NET_F_TSO4_ECN))
+                        dev->features |= NETIF_F_TSO_ECN;
+                if (virtio_use_bit(vdev, token, len, VIRTIO_NET_F_TSO6))
+                        dev->features |= NETIF_F_TSO6;
+        }
+
+        /* Configuration may specify what MAC to use.  Otherwise random. */
+        token = vdev->config->find(vdev, VIRTIO_CONFIG_NET_MAC_F, &len);
+        if (token) {
+                dev->addr_len = len;
+                vdev->config->get(vdev, token, dev->dev_addr, len);
+        } else
+                random_ether_addr(dev->dev_addr);
+
+        /* Set up our device-specific information */
+        vi = netdev_priv(dev);
+        netif_napi_add(dev, &vi->napi, virtnet_poll, 16);
+        vi->dev = dev;
+        vi->vdev = vdev;
+
+        /* We expect two virtqueues, receive then send. */
+        vi->rvq = vdev->config->find_vq(vdev, skb_recv_done);
+        if (IS_ERR(vi->rvq)) {
+                err = PTR_ERR(vi->rvq);
+                goto free;
+        }
+
+        vi->svq = vdev->config->find_vq(vdev, skb_xmit_done);
+        if (IS_ERR(vi->svq)) {
+                err = PTR_ERR(vi->svq);
+                goto free_recv;
+        }
+
+        /* Initialize our empty receive and send queues. */
+        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_send;
+        }
+        pr_debug("virtnet: registered device %s\n", dev->name);
+        vdev->priv = vi;
+        return 0;
+
+free_send:
+        vdev->config->del_vq(vi->svq);
+free_recv:
+        vdev->config->del_vq(vi->rvq);
+free:
+        free_netdev(dev);
+        return err;
+}
+
+static void virtnet_remove(struct virtio_device *vdev)
+{
+        unregister_netdev(vdev->priv);
+        free_netdev(vdev->priv);
+}
+
+static struct virtio_device_id id_table[] = {
+        { VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
+        { 0 },
+};
+
+static struct virtio_driver virtio_net = {
+        .driver.name =  KBUILD_MODNAME,
+        .driver.owner = THIS_MODULE,
+        .id_table =     id_table,
+        .probe =        virtnet_probe,
+        .remove =       __devexit_p(virtnet_remove),
+};
+
+static int __init init(void)
+{
+        return register_virtio_driver(&virtio_net);
+}
+
+static void __exit fini(void)
+{
+        unregister_virtio_driver(&virtio_net);
+}
+module_init(init);
+module_exit(fini);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio network driver");
+MODULE_LICENSE("GPL");