[PATCH 3/6] virtio net driver

Rusty Russell
2007-09-20T12:14:55Z

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 (someone sent patch IIRC?)

Signed-off-by: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
---
drivers/net/Kconfig | 6
drivers/net/Makefile | 2
drivers/net/virtio_net.c | 438 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/virtio_net.h | 36 +++
4 files changed, 481 insertions(+), 1 deletion(-)

===================================================================
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -2998,4 +2998,10 @@ config NET_POLL_CONTROLLER
config NET_POLL_CONTROLLER
def_bool NETPOLL

+config VIRTIO_NET
+ tristate "Virtio network driver (EXPERIMENTAL)"
+ depends on EXPERIMENTAL && VIRTIO
+ ---help---
+ This is the virtual network driver for lguest. Say Y or M.
+
endif # NETDEVICES
===================================================================
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -38,7 +38,7 @@ obj-$(CONFIG_SUNVNET) += sunvnet.o

obj-$(CONFIG_MACE) += mace.o
obj-$(CONFIG_BMAC) += bmac.o
-
+obj-$(CONFIG_VIRTIO_NET) += virtio_net.o
obj-$(CONFIG_DGRS) += dgrs.o
obj-$(CONFIG_VORTEX) += 3c59x.o
obj-$(CONFIG_TYPHOON) += typhoon.o
===================================================================
--- /dev/null
+++ b/drivers/net/virtio_net.c
@@ -0,0 +1,438 @@
+/* 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/virtio_net.h>
+#include <linux/scatterlist.h>
+
+/* FIXME: MTU in config. */
+#define MAX_PACKET_LEN (ETH_HLEN+ETH_DATA_LEN)
+
+struct virtnet_info
+{
+ struct virtqueue_ops *vq_ops;
+ struct virtqueue *vq_recv;
+ struct virtqueue *vq_send;
+ 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 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(void *ndev)
+{
+ /* In case we were waiting for output buffers. */
+ netif_wake_queue(ndev);
+ 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->ndev, 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->vq_ops->add_buf(vi->vq_recv, 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->vq_ops->kick(vi->vq_recv);
+}
+
+static bool skb_recv_done(void *ndev)
+{
+ netif_rx_schedule(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->vq_ops->get_buf(vi->vq_recv, &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->vq_ops->restart(vi->vq_recv))
+ && 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->vq_ops->get_buf(vi->vq_send, &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);
+ 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;
+
+ 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);
+
+ /* 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->vq_ops->add_buf(vi->vq_send, 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->vq_ops->kick(vi->vq_send);
+
+ 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(). */
+ vi->vq_ops->shutdown(vi->vq_recv);
+ while ((skb = __skb_dequeue(&vi->recv)) != NULL) {
+ kfree_skb(skb);
+ vi->num--;
+ }
+ vi->vq_ops->shutdown(vi->vq_send);
+ while ((skb = __skb_dequeue(&vi->send)) != NULL)
+ kfree_skb(skb);
+
+ BUG_ON(vi->num != 0);
+ return 0;
+}
+
+static void *virtnet_probe(struct device *device,
+ struct virtio_config_space *config,
+ struct virtqueue_ops *vq_ops)
+{
+ int err, coff;
+ unsigned int len;
+ struct net_device *dev;
+ struct virtnet_info *vi;
+
+ /* Allocate ourselves a network device with room for our info */
+ dev = alloc_etherdev(sizeof(struct virtnet_info));
+ if (!dev)
+ return ERR_PTR(-ENOMEM);
+
+ /* Set up network device as normal. */
+ SET_MODULE_OWNER(dev);
+ ether_setup(dev);
+ dev->open = virtnet_open;
+ dev->stop = virtnet_close;
+ dev->poll = virtnet_poll;
+ dev->hard_start_xmit = start_xmit;
+ dev->weight = 16;
+ dev->features = NETIF_F_HIGHDMA;
+ SET_NETDEV_DEV(dev, device);
+
+ /* Do we support "hardware" checksums? */
+ coff = virtio_config_find(config, VIRTIO_CONFIG_NET_F, &len);
+ if (virtio_use_bit(config, coff, 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(config, coff, len, VIRTIO_NET_F_TSO4))
+ dev->features |= NETIF_F_TSO;
+ if (virtio_use_bit(config, coff, len, VIRTIO_NET_F_UFO))
+ dev->features |= NETIF_F_UFO;
+ if (virtio_use_bit(config, coff, len, VIRTIO_NET_F_TSO4_ECN))
+ dev->features |= NETIF_F_TSO_ECN;
+ if (virtio_use_bit(config, coff, len, VIRTIO_NET_F_TSO6))
+ dev->features |= NETIF_F_TSO6;
+ }
+
+ /* Configuration may specify what MAC to use. Otherwise random. */
+ coff = virtio_config_find(config, VIRTIO_CONFIG_NET_MAC_F, &len);
+ if (coff >= 0) {
+ dev->addr_len = len;
+ virtio_config_get(config, coff, len, dev->dev_addr);
+ } else
+ random_ether_addr(dev->dev_addr);
+
+ /* Set up our device-specific information */
+ vi = netdev_priv(dev);
+ vi->ndev = dev;
+ vi->vq_ops = vq_ops;
+
+ /* We expect two virtqueues, receive then send. */
+ vi->vq_recv = virtio_config_vq(config, vq_ops, device,
+ skb_recv_done, dev);
+ if (IS_ERR(vi->vq_recv)) {
+ err = PTR_ERR(vi->vq_recv);
+ goto free;
+ }
+
+ vi->vq_send = virtio_config_vq(config, vq_ops, device,
+ skb_xmit_done, dev);
+ if (IS_ERR(vi->vq_send)) {
+ err = PTR_ERR(vi->vq_send);
+ 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);
+ return dev;
+
+free_send:
+ vq_ops->free_vq(vi->vq_send);
+free_recv:
+ vq_ops->free_vq(vi->vq_recv);
+free:
+ free_netdev(dev);
+ return ERR_PTR(err);
+}
+
+static void virtnet_remove(void *dev)
+{
+ unregister_netdev(dev);
+ free_netdev(dev);
+}
+
+static struct pci_device_id id_table[] = {
+ VIRTIO_DEV_ID(VIRTIO_ID_NET, PCI_CLASS_NETWORK_OTHER),
+ { 0 },
+};
+
+static struct virtio_driver virtio_net = {
+ .name = KBUILD_MODNAME,
+ .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(pci, id_table);
+MODULE_DESCRIPTION("Virtio network driver");
+MODULE_LICENSE("GPL");
===================================================================
--- /dev/null
+++ b/include/linux/virtio_net.h
@@ -0,0 +1,36 @@
+#ifndef _LINUX_VIRTIO_NET_H
+#define _LINUX_VIRTIO_NET_H
+#include <linux/virtio_config.h>
+
+/* The ID for virtio_net */
+#define VIRTIO_ID_NET 1
+
+/* The bitmap of config for virtio net */
+#define VIRTIO_CONFIG_NET_F 0x40
+#define VIRTIO_NET_F_NO_CSUM 1
+#define VIRTIO_NET_F_TSO4 2
+#define VIRTIO_NET_F_UFO 4
+#define VIRTIO_NET_F_TSO4_ECN 8
+#define VIRTIO_NET_F_TSO6 16
+
+/* The config defining mac address. */
+#define VIRTIO_CONFIG_NET_MAC_F 0x41
+
+/* This is the first element of the scatter-gather list. If you don't
+ * specify GSO or CSUM features, you can simply ignore the header. */
+struct virtio_net_hdr
+{
+#define VIRTIO_NET_HDR_F_NEEDS_CSUM 1 // Use csum_start, csum_offset
+ __u8 flags;
+#define VIRTIO_NET_HDR_GSO_NONE 0 // Not a GSO frame
+#define VIRTIO_NET_HDR_GSO_TCPV4 1 // GSO frame, IPv4 TCP (TSO)
+/* FIXME: Do we need this? If they said they can handle ECN, do they care? */
+#define VIRTIO_NET_HDR_GSO_TCPV4_ECN 2 // GSO frame, IPv4 TCP w/ ECN
+#define VIRTIO_NET_HDR_GSO_UDP 3 // GSO frame, IPv4 UDP (UFO)
+#define VIRTIO_NET_HDR_GSO_TCPV6 4 // GSO frame, IPv6 TCP
+ __u8 gso_type;
+ __u16 gso_size;
+ __u16 csum_start;
+ __u16 csum_offset;
+};
+#endif /* _LINUX_VIRTIO_NET_H */