vhost: multiqueue support

This patch lets vhost support multiqueue. The idea is simple, just launching
multiple threads of vhost and let each of vhost thread processing a subset of
the virtqueues of the device. After this change each emulated device can have
multiple vhost threads as its backend.

To do this, a virtqueue index were introduced to record to first virtqueue that
will be handled by this vhost_net device. Based on this and nvqs, vhost could
calculate its relative index to setup vhost_net device.

Since we may have many vhost/net devices for a virtio-net device. The setting of
guest notifiers were moved out of the starting/stopping of a specific vhost
thread. The vhost_net_{start|stop}() were renamed to
vhost_net_{start|stop}_one(), and a new vhost_net_{start|stop}() were introduced
to configure the guest notifiers and start/stop all vhost/vhost_net devices.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 36 insertions, 46 deletions

diff --git a/hw/vhost.c b/hw/vhost.c
index 0dd2a9aa40..8d41fdb53f 100644
--- a/hw/vhost.c
+++ b/hw/vhost.c
@@ -616,14 +616,17 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
 {
     hwaddr s, l, a;
     int r;
+    int vhost_vq_index = idx - dev->vq_index;
     struct vhost_vring_file file = {
-        .index = idx,
+        .index = vhost_vq_index
     };
     struct vhost_vring_state state = {
-        .index = idx,
+        .index = vhost_vq_index
     };
     struct VirtQueue *vvq = virtio_get_queue(vdev, idx);
 
+    assert(idx >= dev->vq_index && idx < dev->vq_index + dev->nvqs);
+
     vq->num = state.num = virtio_queue_get_num(vdev, idx);
     r = ioctl(dev->control, VHOST_SET_VRING_NUM, &state);
     if (r) {
@@ -666,11 +669,12 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
         goto fail_alloc_ring;
     }
 
-    r = vhost_virtqueue_set_addr(dev, vq, idx, dev->log_enabled);
+    r = vhost_virtqueue_set_addr(dev, vq, vhost_vq_index, dev->log_enabled);
     if (r < 0) {
         r = -errno;
         goto fail_alloc;
     }
+
     file.fd = event_notifier_get_fd(virtio_queue_get_host_notifier(vvq));
     r = ioctl(dev->control, VHOST_SET_VRING_KICK, &file);
     if (r) {
@@ -706,9 +710,10 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
                                     unsigned idx)
 {
     struct vhost_vring_state state = {
-        .index = idx,
+        .index = idx - dev->vq_index
     };
     int r;
+    assert(idx >= dev->vq_index && idx < dev->vq_index + dev->nvqs);
     r = ioctl(dev->control, VHOST_GET_VRING_BASE, &state);
     if (r < 0) {
         fprintf(stderr, "vhost VQ %d ring restore failed: %d\n", idx, r);
@@ -864,7 +869,9 @@ int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
     }
 
     for (i = 0; i < hdev->nvqs; ++i) {
-        r = vdev->binding->set_host_notifier(vdev->binding_opaque, i, true);
+        r = vdev->binding->set_host_notifier(vdev->binding_opaque,
+                                             hdev->vq_index + i,
+                                             true);
         if (r < 0) {
             fprintf(stderr, "vhost VQ %d notifier binding failed: %d\n", i, -r);
             goto fail_vq;
@@ -874,7 +881,9 @@ int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
     return 0;
 fail_vq:
     while (--i >= 0) {
-        r = vdev->binding->set_host_notifier(vdev->binding_opaque, i, false);
+        r = vdev->binding->set_host_notifier(vdev->binding_opaque,
+                                             hdev->vq_index + i,
+                                             false);
         if (r < 0) {
             fprintf(stderr, "vhost VQ %d notifier cleanup error: %d\n", i, -r);
             fflush(stderr);
@@ -895,7 +904,9 @@ void vhost_dev_disable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
     int i, r;
 
     for (i = 0; i < hdev->nvqs; ++i) {
-        r = vdev->binding->set_host_notifier(vdev->binding_opaque, i, false);
+        r = vdev->binding->set_host_notifier(vdev->binding_opaque,
+                                             hdev->vq_index + i,
+                                             false);
         if (r < 0) {
             fprintf(stderr, "vhost VQ %d notifier cleanup failed: %d\n", i, -r);
             fflush(stderr);
@@ -909,8 +920,9 @@ void vhost_dev_disable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
  */
 bool vhost_virtqueue_pending(struct vhost_dev *hdev, int n)
 {
-    struct vhost_virtqueue *vq = hdev->vqs + n;
+    struct vhost_virtqueue *vq = hdev->vqs + n - hdev->vq_index;
     assert(hdev->started);
+    assert(n >= hdev->vq_index && n < hdev->vq_index + hdev->nvqs);
     return event_notifier_test_and_clear(&vq->masked_notifier);
 }
 
@@ -919,15 +931,16 @@ void vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
                          bool mask)
 {
     struct VirtQueue *vvq = virtio_get_queue(vdev, n);
-    int r;
+    int r, index = n - hdev->vq_index;
 
     assert(hdev->started);
+    assert(n >= hdev->vq_index && n < hdev->vq_index + hdev->nvqs);
 
     struct vhost_vring_file file = {
-        .index = n,
+        .index = index
     };
     if (mask) {
-        file.fd = event_notifier_get_fd(&hdev->vqs[n].masked_notifier);
+        file.fd = event_notifier_get_fd(&hdev->vqs[index].masked_notifier);
     } else {
         file.fd = event_notifier_get_fd(virtio_queue_get_guest_notifier(vvq));
     }
@@ -942,20 +955,6 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
 
     hdev->started = true;
 
-    if (!vdev->binding->set_guest_notifiers) {
-        fprintf(stderr, "binding does not support guest notifiers\n");
-        r = -ENOSYS;
-        goto fail;
-    }
-
-    r = vdev->binding->set_guest_notifiers(vdev->binding_opaque,
-                                           hdev->nvqs,
-                                           true);
-    if (r < 0) {
-        fprintf(stderr, "Error binding guest notifier: %d\n", -r);
-        goto fail_notifiers;
-    }
-
     r = vhost_dev_set_features(hdev, hdev->log_enabled);
     if (r < 0) {
         goto fail_features;
@@ -967,9 +966,9 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
     }
     for (i = 0; i < hdev->nvqs; ++i) {
         r = vhost_virtqueue_start(hdev,
-                                 vdev,
-                                 hdev->vqs + i,
-                                 i);
+                                  vdev,
+                                  hdev->vqs + i,
+                                  hdev->vq_index + i);
         if (r < 0) {
             goto fail_vq;
         }
@@ -992,15 +991,13 @@ fail_log:
 fail_vq:
     while (--i >= 0) {
         vhost_virtqueue_stop(hdev,
-                                vdev,
-                                hdev->vqs + i,
-                                i);
+                             vdev,
+                             hdev->vqs + i,
+                             hdev->vq_index + i);
     }
+    i = hdev->nvqs;
 fail_mem:
 fail_features:
-    vdev->binding->set_guest_notifiers(vdev->binding_opaque, hdev->nvqs, false);
-fail_notifiers:
-fail:
 
     hdev->started = false;
     return r;
@@ -1009,29 +1006,22 @@ fail:
 /* Host notifiers must be enabled at this point. */
 void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
 {
-    int i, r;
+    int i;
 
     for (i = 0; i < hdev->nvqs; ++i) {
         vhost_virtqueue_stop(hdev,
-                                vdev,
-                                hdev->vqs + i,
-                                i);
+                             vdev,
+                             hdev->vqs + i,
+                             hdev->vq_index + i);
     }
     for (i = 0; i < hdev->n_mem_sections; ++i) {
         vhost_sync_dirty_bitmap(hdev, &hdev->mem_sections[i],
                                 0, (hwaddr)~0x0ull);
     }
-    r = vdev->binding->set_guest_notifiers(vdev->binding_opaque,
-                                           hdev->nvqs,
-                                           false);
-    if (r < 0) {
-        fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", r);
-        fflush(stderr);
-    }
-    assert (r >= 0);
 
     hdev->started = false;
     g_free(hdev->log);
     hdev->log = NULL;
     hdev->log_size = 0;
 }
+