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

Anthony Liguori
2007-11-11T03:20:38Z

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>

diff --git a/qemu/Makefile.target b/qemu/Makefile.target
index fedf1e0..8ed5ea9 100644
--- a/qemu/Makefile.target
+++ b/qemu/Makefile.target
@@ -449,7 +449,7 @@ VL_OBJS += rtl8139.o
VL_OBJS+= hypercall.o

# virtio devices
-VL_OBJS += virtio.o virtio-blk.o virtio-9p.o
+VL_OBJS += virtio.o virtio-blk.o virtio-9p.o virtio-net.o

ifeq ($(TARGET_BASE_ARCH), i386)
# Hardware support
diff --git a/qemu/hw/pci.c b/qemu/hw/pci.c
index 7e8adc4..d370988 100644
--- a/qemu/hw/pci.c
+++ b/qemu/hw/pci.c
@@ -588,6 +588,8 @@ void pci_nic_init(PCIBus *bus, NICInfo *nd, int devfn)
pci_rtl8139_init(bus, nd, devfn);
} else if (strcmp(nd->model, "pcnet") == 0) {
pci_pcnet_init(bus, nd, devfn);
+ } else if (strcmp(nd->model, "virtio") == 0) {
+ virtio_net_init(bus, 0x5002, 0x2258, nd, devfn);
} else if (strcmp(nd->model, "?") == 0) {
fprintf(stderr, "qemu: Supported PCI NICs: i82551 i82557b i82559er"
" ne2k_pci pcnet rtl8139\n");
diff --git a/qemu/hw/virtio-net.c b/qemu/hw/virtio-net.c
new file mode 100644
index 0000000..9ed7df7
--- /dev/null
+++ b/qemu/hw/virtio-net.c
@@ -0,0 +1,175 @@
+/*
+ * Virtio Network Device
+ *
+ * Copyright IBM, Corp. 2007
+ *
+ * Authors:
+ * Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "vl.h"
+#include "virtio.h"
+
+/* from Linux's virtio_net.h */
+
+/* The ID for virtio_net */
+#define VIRTIO_ID_NET 1
+
+/* The feature bitmap for virtio net */
+#define VIRTIO_NET_F_NO_CSUM 0
+#define VIRTIO_NET_F_TSO4 1
+#define VIRTIO_NET_F_UFO 2
+#define VIRTIO_NET_F_TSO4_ECN 3
+#define VIRTIO_NET_F_TSO6 4
+#define VIRTIO_NET_F_MAC 5
+
+/* The config defining mac address (6 bytes) */
+#define VIRTIO_CONFIG_NET_MAC_F 0
+
+/* 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
+ uint8_t 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
+ uint8_t gso_type;
+ uint16_t gso_size;
+ uint16_t csum_start;
+ uint16_t csum_offset;
+};
+
+typedef struct VirtIONet
+{
+ VirtIODevice vdev;
+ uint8_t mac[6];
+ VirtQueue *rx_vq;
+ VirtQueue *tx_vq;
+ VLANClientState *vc;
+ int can_receive;
+} VirtIONet;
+
+/* FIXME: there may be a bug where the first dns lookup doesn't work. have to
+ * see if this is a regression */
+
+static VirtIONet *to_virtio_net(VirtIODevice *vdev)
+{
+ return (VirtIONet *)vdev;
+}
+
+static void virtio_net_update_config(VirtIODevice *vdev, uint8_t *config)
+{
+ VirtIONet *n = to_virtio_net(vdev);
+
+ memcpy(config + VIRTIO_CONFIG_NET_MAC_F, n->mac, 6);
+}
+
+static uint32_t virtio_net_get_features(VirtIODevice *vdev)
+{
+ return (1 << VIRTIO_NET_F_MAC);
+}
+
+/* RX */
+
+static void virtio_net_handle_rx(VirtIODevice *vdev, VirtQueue *vq)
+{
+ VirtIONet *n = to_virtio_net(vdev);
+ n->can_receive = 1;
+}
+
+static int virtio_net_can_receive(void *opaque)
+{
+ VirtIONet *n = opaque;
+
+ return (n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK) && n->can_receive;
+}
+
+static void virtio_net_receive(void *opaque, const uint8_t *buf, int size)
+{
+ VirtIONet *n = opaque;
+ VirtQueueElement elem;
+ struct virtio_net_hdr *hdr;
+ int offset, i;
+
+ /* FIXME: the drivers really need to set their status better */
+ if (n->rx_vq->vring.avail == NULL) {
+ n->can_receive = 0;
+ return;
+ }
+
+ if (virtqueue_pop(n->rx_vq, &elem) == 0) {
+ /* wait until the guest adds some rx bufs */
+ n->can_receive = 0;
+ return;
+ }
+
+ hdr = (void *)elem.in_sg[0].iov_base;
+ hdr->flags = 0;
+ hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
+
+ /* copy in packet. ugh */
+ offset = 0;
+ i = 1;
+ while (offset < size && i < elem.in_num) {
+ int len = MIN(elem.in_sg[i].iov_len, size - offset);
+ memcpy(elem.in_sg[i].iov_base, buf + offset, len);
+ offset += len;
+ i++;
+ }
+
+ /* signal other side */
+ virtqueue_push(n->rx_vq, &elem, sizeof(*hdr) + offset);
+ virtio_notify(&n->vdev, n->rx_vq);
+}
+
+/* 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);
+ }
+}
+
+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);