[Qemu-devel] [PATCH 06/12] vhost: multiqueue support

[Jason Wang <jasowang@redhat.com>]

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.

The only thing needed is passing a virtqueue index when starting vhost device,
this is used to track the first virtqueue which this vhost thread serves.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/vhost.c      |   52 +++++++++++++++++++++++++++++++++-------------------
 hw/vhost.h      |    2 ++
 hw/vhost_net.c  |    7 +++++--
 hw/vhost_net.h  |    2 +-
 hw/virtio-net.c |    3 ++-
 5 files changed, 43 insertions(+), 23 deletions(-)

diff --git a/hw/vhost.c b/hw/vhost.c
index 16322a1..63c76d6 100644
--- a/hw/vhost.c
+++ b/hw/vhost.c
@@ -619,11 +619,12 @@ static int vhost_virtqueue_init(struct vhost_dev *dev,
 {
     hwaddr s, l, a;
     int r;
+    int vhost_vq_index = idx % dev->nvqs;
     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);
 
@@ -669,11 +670,12 @@ static int vhost_virtqueue_init(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) {
@@ -714,7 +716,7 @@ static void vhost_virtqueue_cleanup(struct vhost_dev *dev,
                                     unsigned idx)
 {
     struct vhost_vring_state state = {
-        .index = idx,
+        .index = idx % dev->nvqs,
     };
     int r;
     r = ioctl(dev->control, VHOST_GET_VRING_BASE, &state);
@@ -829,7 +831,9 @@ 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;
@@ -839,7 +843,9 @@ 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);
@@ -860,7 +866,9 @@ 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);
@@ -879,10 +887,12 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
         goto fail;
     }
 
-    r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, true);
-    if (r < 0) {
-        fprintf(stderr, "Error binding guest notifier: %d\n", -r);
-        goto fail_notifiers;
+    if (hdev->vq_index == 0) {
+        r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, 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);
@@ -898,7 +908,7 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
         r = vhost_virtqueue_init(hdev,
                                  vdev,
                                  hdev->vqs + i,
-                                 i);
+                                 hdev->vq_index + i);
         if (r < 0) {
             goto fail_vq;
         }
@@ -925,8 +935,9 @@ fail_vq:
         vhost_virtqueue_cleanup(hdev,
                                 vdev,
                                 hdev->vqs + i,
-                                i);
+                                hdev->vq_index + i);
     }
+    i = hdev->nvqs;
 fail_mem:
 fail_features:
     vdev->binding->set_guest_notifiers(vdev->binding_opaque, false);
@@ -944,21 +955,24 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
         vhost_virtqueue_cleanup(hdev,
                                 vdev,
                                 hdev->vqs + i,
-                                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, false);
-    if (r < 0) {
-        fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", r);
-        fflush(stderr);
+    if (hdev->vq_index == 0) {
+        r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, false);
+        if (r < 0) {
+            fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", r);
+            fflush(stderr);
+        }
+        assert (r>= 0);
     }
-    assert (r >= 0);
 
     hdev->started = false;
     g_free(hdev->log);
     hdev->log = NULL;
     hdev->log_size = 0;
 }
+
diff --git a/hw/vhost.h b/hw/vhost.h
index 0c47229..e94a9f7 100644
--- a/hw/vhost.h
+++ b/hw/vhost.h
@@ -34,6 +34,8 @@ struct vhost_dev {
     MemoryRegionSection *mem_sections;
     struct vhost_virtqueue *vqs;
     int nvqs;
+    /* the first virtuque which would be used by this vhost dev */
+    int vq_index;
     unsigned long long features;
     unsigned long long acked_features;
     unsigned long long backend_features;
diff --git a/hw/vhost_net.c b/hw/vhost_net.c
index 8241601..cdb294c 100644
--- a/hw/vhost_net.c
+++ b/hw/vhost_net.c
@@ -138,13 +138,15 @@ bool vhost_net_query(VHostNetState *net, VirtIODevice *dev)
 }
 
 int vhost_net_start(struct vhost_net *net,
-                    VirtIODevice *dev)
+                    VirtIODevice *dev,
+                    int vq_index)
 {
     struct vhost_vring_file file = { };
     int r;
 
     net->dev.nvqs = 2;
     net->dev.vqs = net->vqs;
+    net->dev.vq_index = vq_index;
 
     r = vhost_dev_enable_notifiers(&net->dev, dev);
     if (r < 0) {
@@ -214,7 +216,8 @@ bool vhost_net_query(VHostNetState *net, VirtIODevice *dev)
 }
 
 int vhost_net_start(struct vhost_net *net,
-		    VirtIODevice *dev)
+                    VirtIODevice *dev,
+                    int vq_index)
 {
     return -ENOSYS;
 }
diff --git a/hw/vhost_net.h b/hw/vhost_net.h
index a9db234..c9a8429 100644
--- a/hw/vhost_net.h
+++ b/hw/vhost_net.h
@@ -9,7 +9,7 @@ typedef struct vhost_net VHostNetState;
 VHostNetState *vhost_net_init(NetClientState *backend, int devfd, bool force);
 
 bool vhost_net_query(VHostNetState *net, VirtIODevice *dev);
-int vhost_net_start(VHostNetState *net, VirtIODevice *dev);
+int vhost_net_start(VHostNetState *net, VirtIODevice *dev, int vq_index);
 void vhost_net_stop(VHostNetState *net, VirtIODevice *dev);
 
 void vhost_net_cleanup(VHostNetState *net);
diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index d57a5a5..70bc0e6 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -126,7 +126,8 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
         if (!vhost_net_query(tap_get_vhost_net(qemu_get_queue(n->nic)->peer), &n->vdev)) {
             return;
         }
-        r = vhost_net_start(tap_get_vhost_net(qemu_get_queue(n->nic)->peer), &n->vdev);
+        r = vhost_net_start(tap_get_vhost_net(qemu_get_queue(n->nic)->peer),
+                            &n->vdev, 0);
         if (r < 0) {
             error_report("unable to start vhost net: %d: "
                          "falling back on userspace virtio", -r);
-- 
1.7.1