[Qemu-devel] [PATCH 2/3] virtio network device

[Anthony Liguori <aliguori@us.ibm.com>]

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Subject: [PATCH 2/3] virtio network device
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Avi Kivity <avi@qumranet.com>
Cc: Dor Laor <dor.laor@qumranet.com>

This patch implements the backend support for the virtio network device.  The
device is optimized for virtualized environments by limiting the number of
guest=>host transitions per-packet.  In the best case, the number of
transitions per-packet is < 1.

With some further optimizations, I have been able to obtain 1.5gbit/sec
host=>guest with this driver (compared to the 90mbit/sec from the rtl8139
card).  This requires additional patches not present in this series.

Index: qemu/Makefile.target
===================================================================
--- qemu.orig/Makefile.target	2007-12-04 14:15:20.000000000 -0600
+++ qemu/Makefile.target	2007-12-04 14:43:57.000000000 -0600
@@ -436,7 +436,7 @@
 VL_OBJS += rtl8139.o
 
 # virtio devices
-VL_OBJS += virtio.o
+VL_OBJS += virtio.o virtio-net.o
 
 ifeq ($(TARGET_BASE_ARCH), i386)
 # Hardware support
Index: qemu/hw/pci.c
===================================================================
--- qemu.orig/hw/pci.c	2007-12-04 14:15:20.000000000 -0600
+++ qemu/hw/pci.c	2007-12-04 14:44:06.000000000 -0600
@@ -25,6 +25,7 @@
 #include "pci.h"
 #include "console.h"
 #include "net.h"
+#include "pc.h"
 
 //#define DEBUG_PCI
 
@@ -591,9 +592,11 @@
         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, nd, devfn);
     } else if (strcmp(nd->model, "?") == 0) {
         fprintf(stderr, "qemu: Supported PCI NICs: i82551 i82557b i82559er"
-                        " ne2k_pci pcnet rtl8139\n");
+                        " ne2k_pci pcnet rtl8139 virtio\n");
         exit (1);
     } else {
         fprintf(stderr, "qemu: Unsupported NIC: %s\n", nd->model);
Index: qemu/hw/virtio-net.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ qemu/hw/virtio-net.c	2007-12-04 14:17:37.000000000 -0600
@@ -0,0 +1,178 @@
+/*
+ * Virtio Network Device
+ *
+ * Copyright IBM, Corp. 2007
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "virtio.h"
+#include "net.h"
+#include "pc.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) */
+struct virtio_net_config
+{
+    uint8_t mac[6];
+} __attribute__((packed));
+
+/* 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;
+
+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);
+    struct virtio_net_config netcfg;
+
+    memcpy(netcfg.mac, n->mac, 6);
+    memcpy(config, &netcfg, sizeof(netcfg));
+}
+
+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);
+    }
+}
+
+void *virtio_net_init(PCIBus *bus, NICInfo *nd, int devfn)
+{
+    VirtIONet *n;
+
+    n = (VirtIONet *)virtio_init_pci(bus, "virtio-net", 6900, 0x1000,
+				     0, VIRTIO_ID_NET,
+				     0x02, 0x00, 0x00,
+				     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, 512, virtio_net_handle_rx);
+    n->tx_vq = virtio_add_queue(&n->vdev, 128, 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;
+}
Index: qemu/hw/pc.h
===================================================================
--- qemu.orig/hw/pc.h	2007-12-04 14:15:20.000000000 -0600
+++ qemu/hw/pc.h	2007-12-04 14:43:57.000000000 -0600
@@ -142,4 +142,9 @@
 
 void isa_ne2000_init(int base, qemu_irq irq, NICInfo *nd);
 
+/* virtio-net.c */
+
+void *virtio_net_init(PCIBus *bus, NICInfo *nd, int devfn);
+
+
 #endif