qemu/hw/vhost_net.c
mst@redhat.com 5430a28fe4 vhost: force vhost off for non-MSI guests
When MSI is off, each interrupt needs to be bounced through the io
thread when it's set/cleared, so vhost-net causes more context switches and
higher CPU utilization than userspace virtio which handles networking in
the same thread.

We'll need to fix this by adding level irq support in kvm irqfd,
for now disable vhost-net in these configurations.

Added a vhostforce flag to force vhost-net back on.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2011-02-01 16:50:44 -06:00

230 lines
5.9 KiB
C

/*
* vhost-net support
*
* Copyright Red Hat, Inc. 2010
*
* Authors:
* Michael S. Tsirkin <mst@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*/
#include "net.h"
#include "net/tap.h"
#include "virtio-net.h"
#include "vhost_net.h"
#include "config.h"
#ifdef CONFIG_VHOST_NET
#include <linux/vhost.h>
#include <sys/socket.h>
#include <linux/kvm.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/virtio_ring.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <stdio.h>
#include "vhost.h"
struct vhost_net {
struct vhost_dev dev;
struct vhost_virtqueue vqs[2];
int backend;
VLANClientState *vc;
};
unsigned vhost_net_get_features(struct vhost_net *net, unsigned features)
{
/* Clear features not supported by host kernel. */
if (!(net->dev.features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY))) {
features &= ~(1 << VIRTIO_F_NOTIFY_ON_EMPTY);
}
if (!(net->dev.features & (1 << VIRTIO_RING_F_INDIRECT_DESC))) {
features &= ~(1 << VIRTIO_RING_F_INDIRECT_DESC);
}
if (!(net->dev.features & (1 << VIRTIO_NET_F_MRG_RXBUF))) {
features &= ~(1 << VIRTIO_NET_F_MRG_RXBUF);
}
return features;
}
void vhost_net_ack_features(struct vhost_net *net, unsigned features)
{
net->dev.acked_features = net->dev.backend_features;
if (features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY)) {
net->dev.acked_features |= (1 << VIRTIO_F_NOTIFY_ON_EMPTY);
}
if (features & (1 << VIRTIO_RING_F_INDIRECT_DESC)) {
net->dev.acked_features |= (1 << VIRTIO_RING_F_INDIRECT_DESC);
}
if (features & (1 << VIRTIO_NET_F_MRG_RXBUF)) {
net->dev.acked_features |= (1 << VIRTIO_NET_F_MRG_RXBUF);
}
}
static int vhost_net_get_fd(VLANClientState *backend)
{
switch (backend->info->type) {
case NET_CLIENT_TYPE_TAP:
return tap_get_fd(backend);
default:
fprintf(stderr, "vhost-net requires tap backend\n");
return -EBADFD;
}
}
struct vhost_net *vhost_net_init(VLANClientState *backend, int devfd,
bool force)
{
int r;
struct vhost_net *net = qemu_malloc(sizeof *net);
if (!backend) {
fprintf(stderr, "vhost-net requires backend to be setup\n");
goto fail;
}
r = vhost_net_get_fd(backend);
if (r < 0) {
goto fail;
}
net->vc = backend;
net->dev.backend_features = tap_has_vnet_hdr(backend) ? 0 :
(1 << VHOST_NET_F_VIRTIO_NET_HDR);
net->backend = r;
r = vhost_dev_init(&net->dev, devfd, force);
if (r < 0) {
goto fail;
}
if (!tap_has_vnet_hdr_len(backend,
sizeof(struct virtio_net_hdr_mrg_rxbuf))) {
net->dev.features &= ~(1 << VIRTIO_NET_F_MRG_RXBUF);
}
if (~net->dev.features & net->dev.backend_features) {
fprintf(stderr, "vhost lacks feature mask %" PRIu64 " for backend\n",
(uint64_t)(~net->dev.features & net->dev.backend_features));
vhost_dev_cleanup(&net->dev);
goto fail;
}
/* Set sane init value. Override when guest acks. */
vhost_net_ack_features(net, 0);
return net;
fail:
qemu_free(net);
return NULL;
}
bool vhost_net_query(VHostNetState *net, VirtIODevice *dev)
{
return vhost_dev_query(&net->dev, dev);
}
int vhost_net_start(struct vhost_net *net,
VirtIODevice *dev)
{
struct vhost_vring_file file = { };
int r;
if (net->dev.acked_features & (1 << VIRTIO_NET_F_MRG_RXBUF)) {
tap_set_vnet_hdr_len(net->vc,
sizeof(struct virtio_net_hdr_mrg_rxbuf));
}
net->dev.nvqs = 2;
net->dev.vqs = net->vqs;
r = vhost_dev_start(&net->dev, dev);
if (r < 0) {
return r;
}
net->vc->info->poll(net->vc, false);
qemu_set_fd_handler(net->backend, NULL, NULL, NULL);
file.fd = net->backend;
for (file.index = 0; file.index < net->dev.nvqs; ++file.index) {
r = ioctl(net->dev.control, VHOST_NET_SET_BACKEND, &file);
if (r < 0) {
r = -errno;
goto fail;
}
}
return 0;
fail:
file.fd = -1;
while (file.index-- > 0) {
int r = ioctl(net->dev.control, VHOST_NET_SET_BACKEND, &file);
assert(r >= 0);
}
net->vc->info->poll(net->vc, true);
vhost_dev_stop(&net->dev, dev);
if (net->dev.acked_features & (1 << VIRTIO_NET_F_MRG_RXBUF)) {
tap_set_vnet_hdr_len(net->vc, sizeof(struct virtio_net_hdr));
}
return r;
}
void vhost_net_stop(struct vhost_net *net,
VirtIODevice *dev)
{
struct vhost_vring_file file = { .fd = -1 };
for (file.index = 0; file.index < net->dev.nvqs; ++file.index) {
int r = ioctl(net->dev.control, VHOST_NET_SET_BACKEND, &file);
assert(r >= 0);
}
net->vc->info->poll(net->vc, true);
vhost_dev_stop(&net->dev, dev);
if (net->dev.acked_features & (1 << VIRTIO_NET_F_MRG_RXBUF)) {
tap_set_vnet_hdr_len(net->vc, sizeof(struct virtio_net_hdr));
}
}
void vhost_net_cleanup(struct vhost_net *net)
{
vhost_dev_cleanup(&net->dev);
if (net->dev.acked_features & (1 << VIRTIO_NET_F_MRG_RXBUF)) {
tap_set_vnet_hdr_len(net->vc, sizeof(struct virtio_net_hdr));
}
qemu_free(net);
}
#else
struct vhost_net *vhost_net_init(VLANClientState *backend, int devfd,
bool force)
{
return NULL;
}
bool vhost_net_query(VHostNetState *net, VirtIODevice *dev)
{
return false;
}
int vhost_net_start(struct vhost_net *net,
VirtIODevice *dev)
{
return -ENOSYS;
}
void vhost_net_stop(struct vhost_net *net,
VirtIODevice *dev)
{
}
void vhost_net_cleanup(struct vhost_net *net)
{
}
unsigned vhost_net_get_features(struct vhost_net *net, unsigned features)
{
return features;
}
void vhost_net_ack_features(struct vhost_net *net, unsigned features)
{
}
#endif