vhost: enable vhost without without MSI-X

We use vhostforce to enable vhost even if Guests don't have MSI-X
support and we fall back to QEMU virtio-net.

This gives a very small performance gain, but the disadvantage
is that guest now controls which virtio code is running
(qemu or vhost) so our attack surface is doubled.

This patch will enable vhost unconditionally whenever it's requested.
For compatibility, enable vhost when vhostforce is set, as well.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>

hw/net/vhost_net.c

@@ -163,7 +163,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
     net->dev.vq_index = net->nc->queue_index;
 
     r = vhost_dev_init(&net->dev, options->opaque,
-                       options->backend_type, options->force);
+                       options->backend_type);
     if (r < 0) {
         goto fail;
     }
@@ -188,11 +188,6 @@ fail:
     return NULL;
 }
 
-bool vhost_net_query(VHostNetState *net, VirtIODevice *dev)
-{
-    return vhost_dev_query(&net->dev, dev);
-}
-
 static void vhost_net_set_vq_index(struct vhost_net *net, int vq_index)
 {
     net->dev.vq_index = vq_index;
@@ -424,11 +419,6 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
     return NULL;
 }
 
-bool vhost_net_query(VHostNetState *net, VirtIODevice *dev)
-{
-    return false;
-}
-
 int vhost_net_start(VirtIODevice *dev,
                     NetClientState *ncs,
                     int total_queues)

hw/net/virtio-net.c

@@ -128,10 +128,6 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
     if (!n->vhost_started) {
         int r, i;
 
-        if (!vhost_net_query(get_vhost_net(nc->peer), vdev)) {
-            return;
-        }
-
         /* Any packets outstanding? Purge them to avoid touching rings
          * when vhost is running.
          */

hw/scsi/vhost-scsi.c

@@ -246,7 +246,7 @@ static void vhost_scsi_realize(DeviceState *dev, Error **errp)
     s->dev.backend_features = 0;
 
     ret = vhost_dev_init(&s->dev, (void *)(uintptr_t)vhostfd,
-                         VHOST_BACKEND_TYPE_KERNEL, true);
+                         VHOST_BACKEND_TYPE_KERNEL);
     if (ret < 0) {
         error_setg(errp, "vhost-scsi: vhost initialization failed: %s",
                    strerror(-ret));

hw/virtio/vhost.c

@@ -898,7 +898,7 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq)
 }
 
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
-                   VhostBackendType backend_type, bool force)
+                   VhostBackendType backend_type)
 {
     uint64_t features;
     int i, r;
@@ -961,7 +961,6 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     hdev->started = false;
     hdev->memory_changed = false;
     memory_listener_register(&hdev->memory_listener, &address_space_memory);
-    hdev->force = force;
     return 0;
 fail_vq:
     while (--i >= 0) {
@@ -989,17 +988,6 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
     hdev->vhost_ops->vhost_backend_cleanup(hdev);
 }
 
-bool vhost_dev_query(struct vhost_dev *hdev, VirtIODevice *vdev)
-{
-    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
-    VirtioBusState *vbus = VIRTIO_BUS(qbus);
-    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
-
-    return !k->query_guest_notifiers ||
-           k->query_guest_notifiers(qbus->parent) ||
-           hdev->force;
-}
-
 /* Stop processing guest IO notifications in qemu.
  * Start processing them in vhost in kernel.
  */

include/hw/virtio/vhost.h

@@ -51,7 +51,6 @@ struct vhost_dev {
     bool log_enabled;
     unsigned long long log_size;
     Error *migration_blocker;
-    bool force;
     bool memory_changed;
     hwaddr mem_changed_start_addr;
     hwaddr mem_changed_end_addr;
@@ -61,7 +60,7 @@ struct vhost_dev {
 };
 
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
-                   VhostBackendType backend_type, bool force);
+                   VhostBackendType backend_type);
 void vhost_dev_cleanup(struct vhost_dev *hdev);
 bool vhost_dev_query(struct vhost_dev *hdev, VirtIODevice *vdev);
 int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev);

include/net/vhost_net.h

@@ -11,12 +11,10 @@ typedef struct VhostNetOptions {
     VhostBackendType backend_type;
     NetClientState *net_backend;
     void *opaque;
-    bool force;
 } VhostNetOptions;
 
 struct vhost_net *vhost_net_init(VhostNetOptions *options);
 
-bool vhost_net_query(VHostNetState *net, VirtIODevice *dev);
 int vhost_net_start(VirtIODevice *dev, NetClientState *ncs, int total_queues);
 void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs, int total_queues);
 

net/tap.c

@@ -671,7 +671,6 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
 
         options.backend_type = VHOST_BACKEND_TYPE_KERNEL;
         options.net_backend = &s->nc;
-        options.force = tap->has_vhostforce && tap->vhostforce;
 
         if (tap->has_vhostfd || tap->has_vhostfds) {
             vhostfd = monitor_fd_param(cur_mon, vhostfdname, &err);

net/vhost-user.c

@@ -50,7 +50,6 @@ static int vhost_user_start(VhostUserState *s)
     options.backend_type = VHOST_BACKEND_TYPE_USER;
     options.net_backend = &s->nc;
     options.opaque = s->chr;
-    options.force = true;
 
     s->vhost_net = vhost_net_init(&options);