kvm tools: Add vhost-net support

This patch adds support to using the vhost-net device when using a tap backed virtio-net device. Activating vhost-net is done by appending a 'vhost=1' flag to the net device configuration. For example: 'kvm run -n mode=tap,vhost=1' This improves performance as follows: Short version ------------------ TCP Throughput: +29% UDP Throughput: +10% TCP Latency: -15% UDP Latency: -12% Long version ------------------ MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.33.4 (192.168.33.4) port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 16384 10.00 4895.04 MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.33.4 (192.168.33.4) port 0 AF_INET Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 229376 65507 10.00 125287 0 6565.60 229376 10.00 106910 5602.57 MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.33.4 (192.168.33.4) port 0 AF_INET : first burst 0 Local /Remote Socket Size Request Resp. Elapsed Trans. Send Recv Size Size Time Rate bytes Bytes bytes bytes secs. per sec 16384 87380 1 1 10.00 14811.55 MIGRATED UDP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.33.4 (192.168.33.4) port 0 AF_INET : first burst 0 Local /Remote Socket Size Request Resp. Elapsed Trans. Send Recv Size Size Time Rate bytes Bytes bytes bytes secs. per sec 229376 229376 1 1 10.00 16000.44 229376 229376 After: MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.33.4 (192.168.33.4) port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 16384 10.00 6340.74 MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.33.4 (192.168.33.4) port 0 AF_INET Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 229376 65507 10.00 131478 0 6890.09 229376 10.00 118136 6190.90 MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.33.4 (192.168.33.4) port 0 AF_INET : first burst 0 Local /Remote Socket Size Request Resp. Elapsed Trans. Send Recv Size Size Time Rate bytes Bytes bytes bytes secs. per sec 16384 87380 1 1 10.00 17126.10 MIGRATED UDP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.33.4 (192.168.33.4) port 0 AF_INET : first burst 0 Local /Remote Socket Size Request Resp. Elapsed Trans. Send Recv Size Size Time Rate bytes Bytes bytes bytes secs. per sec 229376 229376 1 1 10.00 17944.51 Cc: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Pekka Enberg <penberg@kernel.org>
2026-09-05 13:11:44 +00:00 · 2015-06-01 16:39:48 +01:00
parent 263b80e8e9
commit 9ed67cdc82
3 changed files with 122 additions and 1 deletions
@@ -217,6 +217,8 @@ static int set_net_param(struct virtio_net_params *p, const char *param,
 		p->guest_ip = strdup(val);
 	} else if (strcmp(param, "host_ip") == 0) {
 		p->host_ip = strdup(val);
+	} else if (strcmp(param, "vhost") == 0) {
+		p->vhost = atoi(val);
 	}

 	return 0;
@@ -11,6 +11,7 @@ struct virtio_net_params {
 	char host_mac[6];
 	struct kvm *kvm;
 	int mode;
+	int vhost;
 };

 void virtio_net__init(const struct virtio_net_params *params);
@@ -10,6 +10,7 @@
 #include "kvm/guest_compat.h"
 #include "kvm/virtio-trans.h"

+#include <linux/vhost.h>
 #include <linux/virtio_net.h>
 #include <linux/if_tun.h>
 #include <linux/types.h>
@@ -25,6 +26,7 @@
 #include <sys/ioctl.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <sys/eventfd.h>

 #define VIRTIO_NET_QUEUE_SIZE		128
 #define VIRTIO_NET_NUM_QUEUES		2
@@ -57,6 +59,7 @@ struct net_dev {
 	pthread_mutex_t			io_tx_lock;
 	pthread_cond_t			io_tx_cond;

+	int				vhost_fd;
 	int				tap_fd;
 	char				tap_name[IFNAMSIZ];

@@ -323,9 +326,12 @@ static void set_guest_features(struct kvm *kvm, void *dev, u32 features)

 static int init_vq(struct kvm *kvm, void *dev, u32 vq, u32 pfn)
 {
+	struct vhost_vring_state state = { .index = vq };
+	struct vhost_vring_addr addr;
 	struct net_dev *ndev = dev;
 	struct virt_queue *queue;
 	void *p;
+	int r;

 	compat__remove_message(compat_id);

@@ -335,9 +341,82 @@ static int init_vq(struct kvm *kvm, void *dev, u32 vq, u32 pfn)

 	vring_init(&queue->vring, VIRTIO_NET_QUEUE_SIZE, p, VIRTIO_PCI_VRING_ALIGN);

+	if (ndev->vhost_fd == 0)
+		return 0;
+
+	state.num = queue->vring.num;
+	r = ioctl(ndev->vhost_fd, VHOST_SET_VRING_NUM, &state);
+	if (r < 0)
+		die_perror("VHOST_SET_VRING_NUM failed");
+	state.num = 0;
+	r = ioctl(ndev->vhost_fd, VHOST_SET_VRING_BASE, &state);
+	if (r < 0)
+		die_perror("VHOST_SET_VRING_BASE failed");
+
+	addr = (struct vhost_vring_addr) {
+		.index = vq,
+		.desc_user_addr = (u64)(unsigned long)queue->vring.desc,
+		.avail_user_addr = (u64)(unsigned long)queue->vring.avail,
+		.used_user_addr = (u64)(unsigned long)queue->vring.used,
+	};
+
+	r = ioctl(ndev->vhost_fd, VHOST_SET_VRING_ADDR, &addr);
+	if (r < 0)
+		die_perror("VHOST_SET_VRING_ADDR failed");
+
 	return 0;
 }

+static void notify_vq_gsi(struct kvm *kvm, void *dev, u32 vq, u32 gsi)
+{
+	struct net_dev *ndev = dev;
+	struct kvm_irqfd irq;
+	struct vhost_vring_file file;
+	int r;
+
+	if (ndev->vhost_fd == 0)
+		return;
+
+	irq = (struct kvm_irqfd) {
+		.gsi	= gsi,
+		.fd	= eventfd(0, 0),
+	};
+	file = (struct vhost_vring_file) {
+		.index	= vq,
+		.fd	= irq.fd,
+	};
+
+	r = ioctl(kvm->vm_fd, KVM_IRQFD, &irq);
+	if (r < 0)
+		die_perror("KVM_IRQFD failed");
+
+	r = ioctl(ndev->vhost_fd, VHOST_SET_VRING_CALL, &file);
+	if (r < 0)
+		die_perror("VHOST_SET_VRING_CALL failed");
+	file.fd = ndev->tap_fd;
+	r = ioctl(ndev->vhost_fd, VHOST_NET_SET_BACKEND, &file);
+	if (r != 0)
+		die("VHOST_NET_SET_BACKEND failed %d", errno);
+
+}
+
+static void notify_vq_eventfd(struct kvm *kvm, void *dev, u32 vq, u32 efd)
+{
+	struct net_dev *ndev = dev;
+	struct vhost_vring_file file = {
+		.index	= vq,
+		.fd	= efd,
+	};
+	int r;
+
+	if (ndev->vhost_fd == 0)
+		return;
+
+	r = ioctl(ndev->vhost_fd, VHOST_SET_VRING_KICK, &file);
+	if (r < 0)
+		die_perror("VHOST_SET_VRING_KICK failed");
+}
+
 static int notify_vq(struct kvm *kvm, void *dev, u32 vq)
 {
 	struct net_dev *ndev = dev;
@@ -368,8 +447,44 @@ static struct virtio_ops net_dev_virtio_ops = (struct virtio_ops) {
 	.notify_vq		= notify_vq,
 	.get_pfn_vq		= get_pfn_vq,
 	.get_size_vq		= get_size_vq,
+	.notify_vq_gsi		= notify_vq_gsi,
+	.notify_vq_eventfd	= notify_vq_eventfd,
 };

+static void virtio_net__vhost_init(struct kvm *kvm, struct net_dev *ndev)
+{
+	u64 features = 0;
+	struct vhost_memory *mem;
+	int r;
+
+	ndev->vhost_fd = open("/dev/vhost-net", O_RDWR);
+	if (ndev->vhost_fd < 0)
+		die_perror("Failed openning vhost-net device");
+
+	mem = malloc(sizeof(*mem) + sizeof(struct vhost_memory_region));
+	if (mem == NULL)
+		die("Failed allocating memory for vhost memory map");
+
+	mem->nregions = 1;
+	mem->regions[0] = (struct vhost_memory_region) {
+		.guest_phys_addr	= 0,
+		.memory_size		= kvm->ram_size,
+		.userspace_addr		= (u64)kvm->ram_start,
+	};
+
+	r = ioctl(ndev->vhost_fd, VHOST_SET_OWNER);
+	if (r != 0)
+		die_perror("VHOST_SET_OWNER failed");
+
+	r = ioctl(ndev->vhost_fd, VHOST_SET_FEATURES, &features);
+	if (r != 0)
+		die_perror("VHOST_SET_FEATURES failed");
+	r = ioctl(ndev->vhost_fd, VHOST_SET_MEM_TABLE, mem);
+	if (r != 0)
+		die_perror("VHOST_SET_MEM_TABLE failed");
+	free(mem);
+}
+
 void virtio_net__init(const struct virtio_net_params *params)
 {
 	int i;
@@ -415,7 +530,10 @@ void virtio_net__init(const struct virtio_net_params *params)
 					VIRTIO_ID_NET, PCI_CLASS_NET);
 	ndev->vtrans.virtio_ops = &net_dev_virtio_ops;

-	virtio_net__io_thread_init(params->kvm, ndev);
+	if (params->vhost)
+		virtio_net__vhost_init(params->kvm, ndev);
+	else
+		virtio_net__io_thread_init(params->kvm, ndev);

 	if (compat_id != -1)
 		compat_id = compat__add_message("virtio-net device was not detected",