[PATCH 0/5] NIC vhost-vdpa state restore via Shadow CVQ

[PATCH 0/5] NIC vhost-vdpa state restore via Shadow CVQ

[Eugenio Pérez]

CVQ of net vhost-vdpa devices can be intercepted since the work of [1]. The
virtio-net device model is updated. The migration was blocked because although
the state can be megrated between VMM it was not possible to restore on the
destination NIC.

This series add support for SVQ to inject external messages without the guest's
knowledge, so before the guest is resumed all the guest visible state is
restored. It is done using standard CVQ messages, so the vhost-vdpa device does
not need to learn how to restore it: As long as they have the feature, they
know how to handle it.

This series needs SVQ CVQ support [1] and fixes [2] to be applied.

Thanks!

[1] https://lists.nongnu.org/archive/html/qemu-devel/2022-07/msg02938.html
[2] https://lists.nongnu.org/archive/html/qemu-devel/2022-07/msg02984.html

v1 from RFC:
- Do not reorder DRIVER_OK & enable patches.
- Delete leftovers

Eugenio Pérez (5):
  vhost: stop transfer elem ownership in vhost_handle_guest_kick
  vdpa: Extract vhost_vdpa_net_cvq_add from
    vhost_vdpa_net_handle_ctrl_avail
  vdpa: Make vhost_vdpa_net_cvq_map_elem accept any out sg
  vdpa: Add virtio-net mac address via CVQ at start
  vdpa: Delete CVQ migration blocker

 include/hw/virtio/vhost-vdpa.h     |   1 -
 include/net/vhost-vdpa.h           |   1 +
 hw/net/vhost_net.c                 |   8 ++
 hw/virtio/vhost-shadow-virtqueue.c |  10 +-
 hw/virtio/vhost-vdpa.c             |  11 --
 net/vhost-vdpa.c                   | 157 +++++++++++++++++++++--------
 6 files changed, 127 insertions(+), 61 deletions(-)

-- 
2.31.1

[PATCH 1/5] vhost: stop transfer elem ownership in vhost_handle_guest_kick

[Eugenio Pérez]

It was easier to allow vhost_svq_add to handle the memory. Now that we
will move SVQDesc to an opaque context, it's better to handle it in the
caller.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index 1646d3cb40..1a50faceb7 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -233,9 +233,6 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq)
 /**
  * Add an element to a SVQ.
  *
- * The caller must check that there is enough slots for the new element. It
- * takes ownership of the element: In case of failure not ENOSPC, it is free.
- *
  * Return -EINVAL if element is invalid, -ENOSPC if dev queue is full
  */
 int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
@@ -252,7 +249,6 @@ int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
 
     ok = vhost_svq_add_split(svq, out_sg, out_num, in_sg, in_num, &qemu_head);
     if (unlikely(!ok)) {
-        g_free(elem);
         return -EINVAL;
     }
 
@@ -293,7 +289,7 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
         virtio_queue_set_notification(svq->vq, false);
 
         while (true) {
-            VirtQueueElement *elem;
+            g_autofree VirtQueueElement *elem;
             int r;
 
             if (svq->next_guest_avail_elem) {
@@ -324,12 +320,14 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
                      * queue the current guest descriptor and ignore kicks
                      * until some elements are used.
                      */
-                    svq->next_guest_avail_elem = elem;
+                    svq->next_guest_avail_elem = g_steal_pointer(&elem);
                 }
 
                 /* VQ is full or broken, just return and ignore kicks */
                 return;
             }
+            /* elem belongs to SVQ or external caller now */
+            elem = NULL;
         }
 
         virtio_queue_set_notification(svq->vq, true);
-- 
2.31.1

[PATCH 2/5] vdpa: Extract vhost_vdpa_net_cvq_add from vhost_vdpa_net_handle_ctrl_avail

[Eugenio Pérez]

So we can reuse to inject state messages.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 net/vhost-vdpa.c | 71 ++++++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 27 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 986e6414b4..fa00928854 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -334,6 +334,43 @@ static bool vhost_vdpa_net_cvq_map_elem(VhostVDPAState *s,
     return true;
 }
 
+static virtio_net_ctrl_ack vhost_vdpa_net_cvq_add(VhostShadowVirtqueue *svq,
+                                               const struct iovec *dev_buffers)
+{
+    /* in buffer used for device model */
+    virtio_net_ctrl_ack status;
+    size_t dev_written;
+    int r;
+    void *unused = (void *)1;
+
+    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, unused);
+    if (unlikely(r != 0)) {
+        if (unlikely(r == -ENOSPC)) {
+            qemu_log_mask(LOG_GUEST_ERROR, "%s: No space on device queue\n",
+                          __func__);
+        }
+        return VIRTIO_NET_ERR;
+    }
+
+    /*
+     * We can poll here since we've had BQL from the time we sent the
+     * descriptor. Also, we need to take the answer before SVQ pulls by itself,
+     * when BQL is released
+     */
+    dev_written = vhost_svq_poll(svq);
+    if (unlikely(dev_written < sizeof(status))) {
+        error_report("Insufficient written data (%zu)", dev_written);
+        return VIRTIO_NET_ERR;
+    }
+
+    memcpy(&status, dev_buffers[1].iov_base, sizeof(status));
+    if (status != VIRTIO_NET_OK) {
+        return VIRTIO_NET_ERR;
+    }
+
+    return VIRTIO_NET_OK;
+}
+
 /**
  * Do not forward commands not supported by SVQ. Otherwise, the device could
  * accept it and qemu would not know how to update the device model.
@@ -380,19 +417,18 @@ static int vhost_vdpa_net_handle_ctrl_avail(VhostShadowVirtqueue *svq,
                                             void *opaque)
 {
     VhostVDPAState *s = opaque;
-    size_t in_len, dev_written;
+    size_t in_len;
     virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
     /* out and in buffers sent to the device */
     struct iovec dev_buffers[2] = {
         { .iov_base = s->cvq_cmd_out_buffer },
         { .iov_base = s->cvq_cmd_in_buffer },
     };
-    /* in buffer used for device model */
+    /* in buffer seen by virtio-net device model */
     const struct iovec in = {
         .iov_base = &status,
         .iov_len = sizeof(status),
     };
-    int r;
     bool ok;
 
     ok = vhost_vdpa_net_cvq_map_elem(s, elem, dev_buffers);
@@ -405,35 +441,16 @@ static int vhost_vdpa_net_handle_ctrl_avail(VhostShadowVirtqueue *svq,
         goto out;
     }
 
-    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, elem);
-    if (unlikely(r != 0)) {
-        if (unlikely(r == -ENOSPC)) {
-            qemu_log_mask(LOG_GUEST_ERROR, "%s: No space on device queue\n",
-                          __func__);
-        }
-        goto out;
-    }
-
-    /*
-     * We can poll here since we've had BQL from the time we sent the
-     * descriptor. Also, we need to take the answer before SVQ pulls by itself,
-     * when BQL is released
-     */
-    dev_written = vhost_svq_poll(svq);
-    if (unlikely(dev_written < sizeof(status))) {
-        error_report("Insufficient written data (%zu)", dev_written);
-        goto out;
-    }
-
-    memcpy(&status, dev_buffers[1].iov_base, sizeof(status));
+    status = vhost_vdpa_net_cvq_add(svq, dev_buffers);
     if (status != VIRTIO_NET_OK) {
         goto out;
     }
 
     status = VIRTIO_NET_ERR;
-    virtio_net_handle_ctrl_iov(svq->vdev, &in, 1, dev_buffers, 1);
-    if (status != VIRTIO_NET_OK) {
+    in_len = virtio_net_handle_ctrl_iov(svq->vdev, &in, 1, dev_buffers, 1);
+    if (in_len != sizeof(status) || status != VIRTIO_NET_OK) {
         error_report("Bad CVQ processing in model");
+        return VIRTIO_NET_ERR;
     }
 
 out:
@@ -450,7 +467,7 @@ out:
     if (dev_buffers[1].iov_base) {
         vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, dev_buffers[1].iov_base);
     }
-    return r;
+    return status == VIRTIO_NET_OK ? 0 : 1;
 }
 
 static const VhostShadowVirtqueueOps vhost_vdpa_net_svq_ops = {
-- 
2.31.1

[PATCH 3/5] vdpa: Make vhost_vdpa_net_cvq_map_elem accept any out sg

[Eugenio Pérez]

So its generic enough to accept any out sg buffer and we can inject
NIC state messages.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 net/vhost-vdpa.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index fa00928854..533bd9f680 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -302,35 +302,36 @@ dma_map_err:
 }
 
 /**
- * Copy the guest element into a dedicated buffer suitable to be sent to NIC
+ * Maps out sg and in buffer into dedicated buffers suitable to be sent to NIC
  *
- * @iov: [0] is the out buffer, [1] is the in one
+ * @dev_iov: [0] is the out buffer, [1] is the in one
  */
-static bool vhost_vdpa_net_cvq_map_elem(VhostVDPAState *s,
-                                        VirtQueueElement *elem,
-                                        struct iovec *iov)
+static bool vhost_vdpa_net_cvq_map_sg(VhostVDPAState *s,
+                                      const struct iovec *out, size_t out_num,
+                                      struct iovec *dev_iov)
 {
     size_t in_copied;
     bool ok;
 
-    iov[0].iov_base = s->cvq_cmd_out_buffer;
-    ok = vhost_vdpa_cvq_map_buf(&s->vhost_vdpa, elem->out_sg, elem->out_num,
-                                vhost_vdpa_net_cvq_cmd_len(), iov[0].iov_base,
-                                &iov[0].iov_len, false);
+    dev_iov[0].iov_base = s->cvq_cmd_out_buffer;
+    ok = vhost_vdpa_cvq_map_buf(&s->vhost_vdpa, out, out_num,
+                                vhost_vdpa_net_cvq_cmd_len(),
+                                dev_iov[0].iov_base, &dev_iov[0].iov_len,
+                                false);
     if (unlikely(!ok)) {
         return false;
     }
 
-    iov[1].iov_base = s->cvq_cmd_in_buffer;
+    dev_iov[1].iov_base = s->cvq_cmd_in_buffer;
     ok = vhost_vdpa_cvq_map_buf(&s->vhost_vdpa, NULL, 0,
-                                sizeof(virtio_net_ctrl_ack), iov[1].iov_base,
-                                &in_copied, true);
+                                sizeof(virtio_net_ctrl_ack),
+                                dev_iov[1].iov_base, &in_copied, true);
     if (unlikely(!ok)) {
         vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer);
         return false;
     }
 
-    iov[1].iov_len = sizeof(virtio_net_ctrl_ack);
+    dev_iov[1].iov_len = sizeof(virtio_net_ctrl_ack);
     return true;
 }
 
@@ -431,7 +432,7 @@ static int vhost_vdpa_net_handle_ctrl_avail(VhostShadowVirtqueue *svq,
     };
     bool ok;
 
-    ok = vhost_vdpa_net_cvq_map_elem(s, elem, dev_buffers);
+    ok = vhost_vdpa_net_cvq_map_sg(s, elem->out_sg, elem->out_num, dev_buffers);
     if (unlikely(!ok)) {
         goto out;
     }
-- 
2.31.1

[PATCH 4/5] vdpa: Add virtio-net mac address via CVQ at start

[Eugenio Pérez]

This is needed so the destination vdpa device see the same state a the
guest set in the source.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 include/net/vhost-vdpa.h |  1 +
 hw/net/vhost_net.c       |  8 ++++++
 net/vhost-vdpa.c         | 59 ++++++++++++++++++++++++++++++++++++++--
 3 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/include/net/vhost-vdpa.h b/include/net/vhost-vdpa.h
index b81f9a6f2a..38d65e845d 100644
--- a/include/net/vhost-vdpa.h
+++ b/include/net/vhost-vdpa.h
@@ -15,6 +15,7 @@
 #define TYPE_VHOST_VDPA "vhost-vdpa"
 
 struct vhost_net *vhost_vdpa_get_vhost_net(NetClientState *nc);
+int vhost_vdpa_start(NetClientState *nc);
 
 extern const int vdpa_feature_bits[];
 
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index ccac5b7a64..f9cebd9716 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -274,6 +274,13 @@ static int vhost_net_start_one(struct vhost_net *net,
             }
         }
     }
+
+    if (net->nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
+        r = vhost_vdpa_start(net->nc);
+        if (r < 0) {
+            goto fail;
+        }
+    }
     return 0;
 fail:
     file.fd = -1;
@@ -373,6 +380,7 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
         r = vhost_net_start_one(get_vhost_net(peer), dev);
 
         if (r < 0) {
+            vhost_net_stop_one(get_vhost_net(peer), dev);
             goto err_start;
         }
 
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 533bd9f680..e03f026738 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -342,9 +342,12 @@ static virtio_net_ctrl_ack vhost_vdpa_net_cvq_add(VhostShadowVirtqueue *svq,
     virtio_net_ctrl_ack status;
     size_t dev_written;
     int r;
-    void *unused = (void *)1;
 
-    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, unused);
+    /*
+     * Add a fake non-NULL VirtQueueElement since we'll remove before SVQ
+     * event loop can get it.
+     */
+    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, (void *)1);
     if (unlikely(r != 0)) {
         if (unlikely(r == -ENOSPC)) {
             qemu_log_mask(LOG_GUEST_ERROR, "%s: No space on device queue\n",
@@ -372,6 +375,58 @@ static virtio_net_ctrl_ack vhost_vdpa_net_cvq_add(VhostShadowVirtqueue *svq,
     return VIRTIO_NET_OK;
 }
 
+int vhost_vdpa_start(NetClientState *nc)
+{
+    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
+    struct vhost_vdpa *v = &s->vhost_vdpa;
+    VirtIONet *n = VIRTIO_NET(v->dev->vdev);
+    uint64_t features = v->dev->vdev->host_features;
+    VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs, 0);
+
+    if (v->dev->vq_index + v->dev->nvqs != v->dev->vq_index_end) {
+        /* Only interested in CVQ */
+        return 0;
+    }
+
+    assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
+
+    if (features & BIT_ULL(VIRTIO_NET_F_CTRL_MAC_ADDR)) {
+        const struct virtio_net_ctrl_hdr ctrl = {
+            .class = VIRTIO_NET_CTRL_MAC,
+            .cmd = VIRTIO_NET_CTRL_MAC_ADDR_SET,
+        };
+        uint8_t mac[6];
+        const struct iovec out[] = {
+            {
+                .iov_base = (void *)&ctrl,
+                .iov_len = sizeof(ctrl),
+            },{
+                .iov_base = mac,
+                .iov_len = sizeof(mac),
+            },
+        };
+        struct iovec dev_buffers[2] = {
+            { .iov_base = s->cvq_cmd_out_buffer },
+            { .iov_base = s->cvq_cmd_in_buffer },
+        };
+        bool ok;
+        virtio_net_ctrl_ack state;
+
+        ok = vhost_vdpa_net_cvq_map_sg(s, out, ARRAY_SIZE(out), dev_buffers);
+        if (unlikely(!ok)) {
+            return -1;
+        }
+
+        memcpy(mac, n->mac, sizeof(mac));
+        state = vhost_vdpa_net_cvq_add(svq, dev_buffers);
+        vhost_vdpa_cvq_unmap_buf(v, dev_buffers[0].iov_base);
+        vhost_vdpa_cvq_unmap_buf(v, dev_buffers[1].iov_base);
+        return state == VIRTIO_NET_OK ? 0 : 1;
+    }
+
+    return 0;
+}
+
 /**
  * Do not forward commands not supported by SVQ. Otherwise, the device could
  * accept it and qemu would not know how to update the device model.
-- 
2.31.1

[PATCH 5/5] vdpa: Delete CVQ migration blocker

[Eugenio Pérez]

We can restore the device state in the destination via CVQ now. Remove
the migration blocker.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 include/hw/virtio/vhost-vdpa.h |  1 -
 hw/virtio/vhost-vdpa.c         | 11 -----------
 net/vhost-vdpa.c               |  2 --
 3 files changed, 14 deletions(-)

diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index d10a89303e..1111d85643 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -35,7 +35,6 @@ typedef struct vhost_vdpa {
     bool shadow_vqs_enabled;
     /* IOVA mapping used by the Shadow Virtqueue */
     VhostIOVATree *iova_tree;
-    Error *migration_blocker;
     GPtrArray *shadow_vqs;
     const VhostShadowVirtqueueOps *shadow_vq_ops;
     void *shadow_vq_ops_opaque;
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 4458c8d23e..479151bd77 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1023,13 +1023,6 @@ static bool vhost_vdpa_svqs_start(struct vhost_dev *dev)
         return true;
     }
 
-    if (v->migration_blocker) {
-        int r = migrate_add_blocker(v->migration_blocker, &err);
-        if (unlikely(r < 0)) {
-            goto err_migration_blocker;
-        }
-    }
-
     for (i = 0; i < v->shadow_vqs->len; ++i) {
         VirtQueue *vq = virtio_get_queue(dev->vdev, dev->vq_index + i);
         VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs, i);
@@ -1072,7 +1065,6 @@ err:
         vhost_svq_stop(svq);
     }
 
-err_migration_blocker:
     error_reportf_err(err, "Cannot setup SVQ %u: ", i);
 
     return false;
@@ -1094,9 +1086,6 @@ static bool vhost_vdpa_svqs_stop(struct vhost_dev *dev)
         }
     }
 
-    if (v->migration_blocker) {
-        migrate_del_blocker(v->migration_blocker);
-    }
     return true;
 }
 
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index e03f026738..4a39dad47b 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -568,8 +568,6 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
 
         s->vhost_vdpa.shadow_vq_ops = &vhost_vdpa_net_svq_ops;
         s->vhost_vdpa.shadow_vq_ops_opaque = s;
-        error_setg(&s->vhost_vdpa.migration_blocker,
-                   "Migration disabled: vhost-vdpa uses CVQ.");
     }
     ret = vhost_vdpa_add(nc, (void *)&s->vhost_vdpa, queue_pair_index, nvqs);
     if (ret) {
-- 
2.31.1