[PATCH v5 00/14] Dynamically switch to vhost shadow virtqueues at vdpa net migration

[PATCH v5 00/14] Dynamically switch to vhost shadow virtqueues at vdpa net migration

[Eugenio Pérez]

It's possible to migrate vdpa net devices if they are shadowed from the
start.  But to always shadow the dataplane is to effectively break its host
passthrough, so its not efficient in vDPA scenarios.

This series enables dynamically switching to shadow mode only at
migration time.  This allows full data virtqueues passthrough all the
time qemu is not migrating.

In this series only net devices with no CVQ are migratable.  CVQ adds
additional state that would make the series bigger and still had some
controversy on previous RFC, so let's split it.

Successfully tested with vdpa_sim_net with patch [1] applied and with the qemu
emulated device with vp_vdpa with some restrictions:
* No CVQ. No feature that didn't work with SVQ previously (packed, ...)
* VIRTIO_RING_F_STATE patches implementing [2].

Previous versions were tested by many vendors. Not carrying Tested-by because
of code changes, so re-testing would be appreciated.

A ready to clone tag named vdpa.d/stop-nocvq-v5 with this version of the series
is available at https://gitlab.com/eperezmartin/qemu-kvm.git, with the commit
863d54ff00c558ffe54ed2c7ee148ab7f89d4864 ("vdpa: return VHOST_F_LOG_ALL in
vhost-vdpa devices").

Comments are welcome.

v5:
- Reverse SUSPEND polarity check, as qemu was never suspending devices with
  suspend capability.
- Reorder suspend patch so it comes before the reset reorder after
  get_vring_base.
- Remove patch to stop SVQ at vdpa stop, already present in staging

v4:
- Recover used_idx from guest's vring if device cannot suspend.
- Fix starting device in the middle of a migration.  Removed some
  duplication in setting / clearing enable_shadow_vqs and shadow_data
  members of vhost_vdpa.
- Fix (again) "Check for SUSPEND in vhost_dev.backend_cap, as
  .backend_features is empty at the check moment.". It was reverted by
  mistake in v3.
- Fix memory leak of iova tree.
- Properly rewind SVQ as in flight descriptors were still being accounted
  in vq base.
- Expand documentation.

v3:
- Start datapatch in SVQ in device started while migrating.
- Properly register migration blockers if device present unsupported features.
- Fix race condition because of not stopping the SVQ until device cleanup.
- Explain purpose of iova tree in the first patch message.
- s/dynamycally/dynamically/ in cover letter.
- at lore.kernel.org/qemu-devel/20230215173850.298832-14-eperezma@redhat.com

v2:
- Check for SUSPEND in vhost_dev.backend_cap, as .backend_features is empty at
  the check moment.
- at https://lore.kernel.org/all/20230208094253.702672-12-eperezma@redhat.com/T/

v1:
- Omit all code working with CVQ and block migration if the device supports
  CVQ.
- Remove spurious kick.
- Move all possible checks for migration to vhost-vdpa instead of the net
  backend. Move them to init code from start code.
- Suspend on vhost_vdpa_dev_start(false) instead of in vhost-vdpa net backend.
- Properly split suspend after geting base and adding of status_reset patches.
- Add possible TODOs to points where this series can improve in the future.
- Check the state of migration using migration_in_setup and
  migration_has_failed instead of checking all the possible migration status in
  a switch.
- Add TODO with possible low hand fruit using RESUME ops.
- Always offer _F_LOG from virtio/vhost-vdpa and let migration blockers do
  their thing instead of adding a variable.
- RFC v2 at https://lists.gnu.org/archive/html/qemu-devel/2023-01/msg02574.html

RFC v2:
- Use a migration listener instead of a memory listener to know when
  the migration starts.
- Add stuff not picked with ASID patches, like enable rings after
  driver_ok
- Add rewinding on the migration src, not in dst
- RFC v1 at https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg01664.html

[1] https://lore.kernel.org/lkml/20230203142501.300125-1-eperezma@redhat.com/T/
[2] https://lists.oasis-open.org/archives/virtio-comment/202103/msg00036.html

Eugenio Pérez (14):
  vdpa net: move iova tree creation from init to start
  vdpa: Remember last call fd set
  vdpa: Negotiate _F_SUSPEND feature
  vdpa: rewind at get_base, not set_base
  vdpa: add vhost_vdpa->suspended parameter
  vdpa: add vhost_vdpa_suspend
  vdpa: move vhost reset after get vring base
  vdpa: add vdpa net migration state notifier
  vdpa: disable RAM block discard only for the first device
  vdpa net: block migration if the device has CVQ
  vdpa: block migration if device has unsupported features
  vdpa: block migration if SVQ does not admit a feature
  vdpa net: allow VHOST_F_LOG_ALL
  vdpa: return VHOST_F_LOG_ALL in vhost-vdpa devices

 include/hw/virtio/vhost-backend.h  |   4 +
 include/hw/virtio/vhost-vdpa.h     |   3 +
 hw/virtio/vhost-shadow-virtqueue.c |   8 +-
 hw/virtio/vhost-vdpa.c             | 126 ++++++++++++------
 hw/virtio/vhost.c                  |   3 +
 net/vhost-vdpa.c                   | 198 ++++++++++++++++++++++++-----
 hw/virtio/trace-events             |   1 +
 7 files changed, 272 insertions(+), 71 deletions(-)

-- 
2.31.1

[PATCH v5 01/14] vdpa net: move iova tree creation from init to start

[Eugenio Pérez]

Only create iova_tree if and when it is needed.

The cleanup keeps being responsible for the last VQ but this change
allows it to merge both cleanup functions.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
v4:
* Remove leak of iova_tree because double allocation
* Document better the sharing of IOVA tree between data and CVQ
---
 net/vhost-vdpa.c | 113 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 83 insertions(+), 30 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index de5ed8ff22..d195f48776 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -178,13 +178,9 @@ err_init:
 static void vhost_vdpa_cleanup(NetClientState *nc)
 {
     VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
-    struct vhost_dev *dev = &s->vhost_net->dev;
 
     qemu_vfree(s->cvq_cmd_out_buffer);
     qemu_vfree(s->status);
-    if (dev->vq_index + dev->nvqs == dev->vq_index_end) {
-        g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
-    }
     if (s->vhost_net) {
         vhost_net_cleanup(s->vhost_net);
         g_free(s->vhost_net);
@@ -234,10 +230,64 @@ static ssize_t vhost_vdpa_receive(NetClientState *nc, const uint8_t *buf,
     return size;
 }
 
+/** From any vdpa net client, get the netclient of the first queue pair */
+static VhostVDPAState *vhost_vdpa_net_first_nc_vdpa(VhostVDPAState *s)
+{
+    NICState *nic = qemu_get_nic(s->nc.peer);
+    NetClientState *nc0 = qemu_get_peer(nic->ncs, 0);
+
+    return DO_UPCAST(VhostVDPAState, nc, nc0);
+}
+
+static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
+{
+    struct vhost_vdpa *v = &s->vhost_vdpa;
+
+    if (v->shadow_vqs_enabled) {
+        v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
+                                           v->iova_range.last);
+    }
+}
+
+static int vhost_vdpa_net_data_start(NetClientState *nc)
+{
+    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
+    struct vhost_vdpa *v = &s->vhost_vdpa;
+
+    assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
+
+    if (v->index == 0) {
+        vhost_vdpa_net_data_start_first(s);
+        return 0;
+    }
+
+    if (v->shadow_vqs_enabled) {
+        VhostVDPAState *s0 = vhost_vdpa_net_first_nc_vdpa(s);
+        v->iova_tree = s0->vhost_vdpa.iova_tree;
+    }
+
+    return 0;
+}
+
+static void vhost_vdpa_net_client_stop(NetClientState *nc)
+{
+    VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
+    struct vhost_dev *dev;
+
+    assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
+
+    dev = s->vhost_vdpa.dev;
+    if (dev->vq_index + dev->nvqs == dev->vq_index_end) {
+        g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
+    }
+}
+
 static NetClientInfo net_vhost_vdpa_info = {
         .type = NET_CLIENT_DRIVER_VHOST_VDPA,
         .size = sizeof(VhostVDPAState),
         .receive = vhost_vdpa_receive,
+        .start = vhost_vdpa_net_data_start,
+        .stop = vhost_vdpa_net_client_stop,
         .cleanup = vhost_vdpa_cleanup,
         .has_vnet_hdr = vhost_vdpa_has_vnet_hdr,
         .has_ufo = vhost_vdpa_has_ufo,
@@ -351,7 +401,7 @@ dma_map_err:
 
 static int vhost_vdpa_net_cvq_start(NetClientState *nc)
 {
-    VhostVDPAState *s;
+    VhostVDPAState *s, *s0;
     struct vhost_vdpa *v;
     uint64_t backend_features;
     int64_t cvq_group;
@@ -415,8 +465,6 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
         return r;
     }
 
-    v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
-                                       v->iova_range.last);
     v->shadow_vqs_enabled = true;
     s->vhost_vdpa.address_space_id = VHOST_VDPA_NET_CVQ_ASID;
 
@@ -425,6 +473,27 @@ out:
         return 0;
     }
 
+    s0 = vhost_vdpa_net_first_nc_vdpa(s);
+    if (s0->vhost_vdpa.iova_tree) {
+        /*
+         * SVQ is already configured for all virtqueues.  Reuse IOVA tree for
+         * simplicity, whether CVQ shares ASID with guest or not, because:
+         * - Memory listener need access to guest's memory addresses allocated
+         *   in the IOVA tree.
+         * - There should be plenty of IOVA address space for both ASID not to
+         *   worry about collisions between them.  Guest's translations are
+         *   still validated with virtio virtqueue_pop so there is no risk for
+         *   the guest to access memory that it shouldn't.
+         *
+         * To allocate a iova tree per ASID is doable but it complicates the
+         * code and it is not worth it for the moment.
+         */
+        v->iova_tree = s0->vhost_vdpa.iova_tree;
+    } else {
+        v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
+                                           v->iova_range.last);
+    }
+
     r = vhost_vdpa_cvq_map_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer,
                                vhost_vdpa_net_cvq_cmd_page_len(), false);
     if (unlikely(r < 0)) {
@@ -449,15 +518,9 @@ static void vhost_vdpa_net_cvq_stop(NetClientState *nc)
     if (s->vhost_vdpa.shadow_vqs_enabled) {
         vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->cvq_cmd_out_buffer);
         vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, s->status);
-        if (!s->always_svq) {
-            /*
-             * If only the CVQ is shadowed we can delete this safely.
-             * If all the VQs are shadows this will be needed by the time the
-             * device is started again to register SVQ vrings and similar.
-             */
-            g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
-        }
     }
+
+    vhost_vdpa_net_client_stop(nc);
 }
 
 static ssize_t vhost_vdpa_net_cvq_add(VhostVDPAState *s, size_t out_len,
@@ -667,8 +730,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
                                        int nvqs,
                                        bool is_datapath,
                                        bool svq,
-                                       struct vhost_vdpa_iova_range iova_range,
-                                       VhostIOVATree *iova_tree)
+                                       struct vhost_vdpa_iova_range iova_range)
 {
     NetClientState *nc = NULL;
     VhostVDPAState *s;
@@ -690,7 +752,6 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
     s->vhost_vdpa.shadow_vqs_enabled = svq;
     s->vhost_vdpa.iova_range = iova_range;
     s->vhost_vdpa.shadow_data = svq;
-    s->vhost_vdpa.iova_tree = iova_tree;
     if (!is_datapath) {
         s->cvq_cmd_out_buffer = qemu_memalign(qemu_real_host_page_size(),
                                             vhost_vdpa_net_cvq_cmd_page_len());
@@ -760,7 +821,6 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
     uint64_t features;
     int vdpa_device_fd;
     g_autofree NetClientState **ncs = NULL;
-    g_autoptr(VhostIOVATree) iova_tree = NULL;
     struct vhost_vdpa_iova_range iova_range;
     NetClientState *nc;
     int queue_pairs, r, i = 0, has_cvq = 0;
@@ -812,12 +872,8 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
         goto err;
     }
 
-    if (opts->x_svq) {
-        if (!vhost_vdpa_net_valid_svq_features(features, errp)) {
-            goto err_svq;
-        }
-
-        iova_tree = vhost_iova_tree_new(iova_range.first, iova_range.last);
+    if (opts->x_svq && !vhost_vdpa_net_valid_svq_features(features, errp)) {
+        goto err;
     }
 
     ncs = g_malloc0(sizeof(*ncs) * queue_pairs);
@@ -825,7 +881,7 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
     for (i = 0; i < queue_pairs; i++) {
         ncs[i] = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
                                      vdpa_device_fd, i, 2, true, opts->x_svq,
-                                     iova_range, iova_tree);
+                                     iova_range);
         if (!ncs[i])
             goto err;
     }
@@ -833,13 +889,11 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
     if (has_cvq) {
         nc = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
                                  vdpa_device_fd, i, 1, false,
-                                 opts->x_svq, iova_range, iova_tree);
+                                 opts->x_svq, iova_range);
         if (!nc)
             goto err;
     }
 
-    /* iova_tree ownership belongs to last NetClientState */
-    g_steal_pointer(&iova_tree);
     return 0;
 
 err:
@@ -849,7 +903,6 @@ err:
         }
     }
 
-err_svq:
     qemu_close(vdpa_device_fd);
 
     return -1;
-- 
2.31.1

[PATCH v5 02/14] vdpa: Remember last call fd set

[Eugenio Pérez]

As SVQ can be enabled dynamically at any time, it needs to store call fd
always.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index df3a1e92ac..108cd63289 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1227,16 +1227,16 @@ static int vhost_vdpa_set_vring_call(struct vhost_dev *dev,
                                        struct vhost_vring_file *file)
 {
     struct vhost_vdpa *v = dev->opaque;
+    int vdpa_idx = file->index - dev->vq_index;
+    VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs, vdpa_idx);
 
+    /* Remember last call fd because we can switch to SVQ anytime. */
+    vhost_svq_set_svq_call_fd(svq, file->fd);
     if (v->shadow_vqs_enabled) {
-        int vdpa_idx = file->index - dev->vq_index;
-        VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs, vdpa_idx);
-
-        vhost_svq_set_svq_call_fd(svq, file->fd);
         return 0;
-    } else {
-        return vhost_vdpa_set_vring_dev_call(dev, file);
     }
+
+    return vhost_vdpa_set_vring_dev_call(dev, file);
 }
 
 static int vhost_vdpa_get_features(struct vhost_dev *dev,
-- 
2.31.1

[PATCH v5 03/14] vdpa: Negotiate _F_SUSPEND feature

[Eugenio Pérez]

This is needed for qemu to know it can suspend the device to retrieve
its status and enable SVQ with it, so all the process is transparent to
the guest.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 108cd63289..5cfa9d5d27 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -659,7 +659,8 @@ static int vhost_vdpa_set_backend_cap(struct vhost_dev *dev)
     uint64_t features;
     uint64_t f = 0x1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2 |
         0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH |
-        0x1ULL << VHOST_BACKEND_F_IOTLB_ASID;
+        0x1ULL << VHOST_BACKEND_F_IOTLB_ASID |
+        0x1ULL << VHOST_BACKEND_F_SUSPEND;
     int r;
 
     if (vhost_vdpa_call(dev, VHOST_GET_BACKEND_FEATURES, &features)) {
-- 
2.31.1

[PATCH v5 04/14] vdpa: rewind at get_base, not set_base

[Eugenio Pérez]

At this moment it is only possible to migrate to a vdpa device running
with x-svq=on. As a protective measure, the rewind of the inflight
descriptors was done at the destination. That way if the source sent a
virtqueue with inuse descriptors they are always discarded.

Since this series allows to migrate also to passthrough devices with no
SVQ, the right thing to do is to rewind at the source so the base of
vrings are correct.

Support for inflight descriptors may be added in the future.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
v4:
* Use virtqueue_unpop at vhost_svq_stop instead of rewinding at
  vhost_vdpa_get_vring_base.
---
 hw/virtio/vhost-shadow-virtqueue.c |  8 ++++++--
 hw/virtio/vhost-vdpa.c             | 11 -----------
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index 515ccf870d..8361e70d1b 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -694,13 +694,17 @@ void vhost_svq_stop(VhostShadowVirtqueue *svq)
         g_autofree VirtQueueElement *elem = NULL;
         elem = g_steal_pointer(&svq->desc_state[i].elem);
         if (elem) {
-            virtqueue_detach_element(svq->vq, elem, 0);
+            /*
+             * TODO: This is ok for networking, but other kinds of devices
+             * might have problems with just unpop these.
+             */
+            virtqueue_unpop(svq->vq, elem, 0);
         }
     }
 
     next_avail_elem = g_steal_pointer(&svq->next_guest_avail_elem);
     if (next_avail_elem) {
-        virtqueue_detach_element(svq->vq, next_avail_elem, 0);
+        virtqueue_unpop(svq->vq, next_avail_elem, 0);
     }
     svq->vq = NULL;
     g_free(svq->desc_next);
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 5cfa9d5d27..1550b1e26a 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1170,18 +1170,7 @@ static int vhost_vdpa_set_vring_base(struct vhost_dev *dev,
                                        struct vhost_vring_state *ring)
 {
     struct vhost_vdpa *v = dev->opaque;
-    VirtQueue *vq = virtio_get_queue(dev->vdev, ring->index);
 
-    /*
-     * vhost-vdpa devices does not support in-flight requests. Set all of them
-     * as available.
-     *
-     * TODO: This is ok for networking, but other kinds of devices might
-     * have problems with these retransmissions.
-     */
-    while (virtqueue_rewind(vq, 1)) {
-        continue;
-    }
     if (v->shadow_vqs_enabled) {
         /*
          * Device vring base was set at device start. SVQ base is handled by
-- 
2.31.1

[PATCH v5 05/14] vdpa: add vhost_vdpa->suspended parameter

[Eugenio Pérez]

This allows vhost_vdpa to track if it is safe to get the vring base from
the device or not.  If it is not, vhost can fall back to fetch idx from
the guest buffer again.

No functional change intended in this patch, later patches will use this
field.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 include/hw/virtio/vhost-vdpa.h | 2 ++
 hw/virtio/vhost-vdpa.c         | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index 7997f09a8d..4a7d396674 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -42,6 +42,8 @@ typedef struct vhost_vdpa {
     bool shadow_vqs_enabled;
     /* Vdpa must send shadow addresses as IOTLB key for data queues, not GPA */
     bool shadow_data;
+    /* Device suspended successfully */
+    bool suspended;
     /* IOVA mapping used by the Shadow Virtqueue */
     VhostIOVATree *iova_tree;
     GPtrArray *shadow_vqs;
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 1550b1e26a..517e3cdc8d 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1193,6 +1193,14 @@ static int vhost_vdpa_get_vring_base(struct vhost_dev *dev,
         return 0;
     }
 
+    if (!v->suspended) {
+        /*
+         * Cannot trust in value returned by device, let vhost recover used
+         * idx from guest.
+         */
+        return -1;
+    }
+
     ret = vhost_vdpa_call(dev, VHOST_GET_VRING_BASE, ring);
     trace_vhost_vdpa_get_vring_base(dev, ring->index, ring->num);
     return ret;
-- 
2.31.1

[PATCH v5 06/14] vdpa: add vhost_vdpa_suspend

[Eugenio Pérez]

The function vhost.c:vhost_dev_stop fetches the vring base so the vq
state can be migrated to other devices.  However, this is unreliable in
vdpa, since we didn't signal the device to suspend the queues, making
the value fetched useless.

Suspend the device if possible before fetching first and subsequent
vring bases.

Moreover, vdpa totally reset and wipes the device at the last device
before fetch its vrings base, making that operation useless in the last
device. This will be fixed in later patches of this series.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
v5: Fix backend_cap & suspend check polarity.

v4:
* Look for _F_SUSPEND at vhost_dev->backend_cap, not backend_features
* Fall back on reset & fetch used idx from guest's memory
---
 hw/virtio/vhost-vdpa.c | 26 ++++++++++++++++++++++++++
 hw/virtio/trace-events |  1 +
 2 files changed, 27 insertions(+)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 517e3cdc8d..aecc01c6a7 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -692,11 +692,13 @@ static int vhost_vdpa_get_device_id(struct vhost_dev *dev,
 
 static int vhost_vdpa_reset_device(struct vhost_dev *dev)
 {
+    struct vhost_vdpa *v = dev->opaque;
     int ret;
     uint8_t status = 0;
 
     ret = vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &status);
     trace_vhost_vdpa_reset_device(dev, status);
+    v->suspended = false;
     return ret;
 }
 
@@ -1095,6 +1097,29 @@ static void vhost_vdpa_svqs_stop(struct vhost_dev *dev)
     }
 }
 
+static void vhost_vdpa_suspend(struct vhost_dev *dev)
+{
+    struct vhost_vdpa *v = dev->opaque;
+    int r;
+
+    if (!vhost_vdpa_first_dev(dev)) {
+        return;
+    }
+
+    if (dev->backend_cap & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) {
+        trace_vhost_vdpa_suspend(dev);
+        r = ioctl(v->device_fd, VHOST_VDPA_SUSPEND);
+        if (unlikely(r)) {
+            error_report("Cannot suspend: %s(%d)", g_strerror(errno), errno);
+        } else {
+            v->suspended = true;
+            return;
+        }
+    }
+
+    vhost_vdpa_reset_device(dev);
+}
+
 static int vhost_vdpa_dev_start(struct vhost_dev *dev, bool started)
 {
     struct vhost_vdpa *v = dev->opaque;
@@ -1109,6 +1134,7 @@ static int vhost_vdpa_dev_start(struct vhost_dev *dev, bool started)
         }
         vhost_vdpa_set_vring_ready(dev);
     } else {
+        vhost_vdpa_suspend(dev);
         vhost_vdpa_svqs_stop(dev);
         vhost_vdpa_host_notifiers_uninit(dev, dev->nvqs);
     }
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index a87c5f39a2..8f8d05cf9b 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -50,6 +50,7 @@ vhost_vdpa_set_vring_ready(void *dev) "dev: %p"
 vhost_vdpa_dump_config(void *dev, const char *line) "dev: %p %s"
 vhost_vdpa_set_config(void *dev, uint32_t offset, uint32_t size, uint32_t flags) "dev: %p offset: %"PRIu32" size: %"PRIu32" flags: 0x%"PRIx32
 vhost_vdpa_get_config(void *dev, void *config, uint32_t config_len) "dev: %p config: %p config_len: %"PRIu32
+vhost_vdpa_suspend(void *dev) "dev: %p"
 vhost_vdpa_dev_start(void *dev, bool started) "dev: %p started: %d"
 vhost_vdpa_set_log_base(void *dev, uint64_t base, unsigned long long size, int refcnt, int fd, void *log) "dev: %p base: 0x%"PRIx64" size: %llu refcnt: %d fd: %d log: %p"
 vhost_vdpa_set_vring_addr(void *dev, unsigned int index, unsigned int flags, uint64_t desc_user_addr, uint64_t used_user_addr, uint64_t avail_user_addr, uint64_t log_guest_addr) "dev: %p index: %u flags: 0x%x desc_user_addr: 0x%"PRIx64" used_user_addr: 0x%"PRIx64" avail_user_addr: 0x%"PRIx64" log_guest_addr: 0x%"PRIx64
-- 
2.31.1

[PATCH v5 07/14] vdpa: move vhost reset after get vring base

[Eugenio Pérez]

The function vhost.c:vhost_dev_stop calls vhost operation
vhost_dev_start(false). In the case of vdpa it totally reset and wipes
the device, making the fetching of the vring base (virtqueue state) totally
useless.

The kernel backend does not use vhost_dev_start vhost op callback, but
vhost-user do. A patch to make vhost_user_dev_start more similar to vdpa
is desirable, but it can be added on top.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 include/hw/virtio/vhost-backend.h |  4 ++++
 hw/virtio/vhost-vdpa.c            | 22 ++++++++++++++++------
 hw/virtio/vhost.c                 |  3 +++
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index c5ab49051e..ec3fbae58d 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -130,6 +130,9 @@ typedef bool (*vhost_force_iommu_op)(struct vhost_dev *dev);
 
 typedef int (*vhost_set_config_call_op)(struct vhost_dev *dev,
                                        int fd);
+
+typedef void (*vhost_reset_status_op)(struct vhost_dev *dev);
+
 typedef struct VhostOps {
     VhostBackendType backend_type;
     vhost_backend_init vhost_backend_init;
@@ -177,6 +180,7 @@ typedef struct VhostOps {
     vhost_get_device_id_op vhost_get_device_id;
     vhost_force_iommu_op vhost_force_iommu;
     vhost_set_config_call_op vhost_set_config_call;
+    vhost_reset_status_op vhost_reset_status;
 } VhostOps;
 
 int vhost_backend_update_device_iotlb(struct vhost_dev *dev,
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index aecc01c6a7..c9a82ce5e0 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1146,14 +1146,23 @@ static int vhost_vdpa_dev_start(struct vhost_dev *dev, bool started)
     if (started) {
         memory_listener_register(&v->listener, &address_space_memory);
         return vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
-    } else {
-        vhost_vdpa_reset_device(dev);
-        vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
-                                   VIRTIO_CONFIG_S_DRIVER);
-        memory_listener_unregister(&v->listener);
+    }
 
-        return 0;
+    return 0;
+}
+
+static void vhost_vdpa_reset_status(struct vhost_dev *dev)
+{
+    struct vhost_vdpa *v = dev->opaque;
+
+    if (dev->vq_index + dev->nvqs != dev->vq_index_end) {
+        return;
     }
+
+    vhost_vdpa_reset_device(dev);
+    vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
+                               VIRTIO_CONFIG_S_DRIVER);
+    memory_listener_unregister(&v->listener);
 }
 
 static int vhost_vdpa_set_log_base(struct vhost_dev *dev, uint64_t base,
@@ -1337,4 +1346,5 @@ const VhostOps vdpa_ops = {
         .vhost_vq_get_addr = vhost_vdpa_vq_get_addr,
         .vhost_force_iommu = vhost_vdpa_force_iommu,
         .vhost_set_config_call = vhost_vdpa_set_config_call,
+        .vhost_reset_status = vhost_vdpa_reset_status,
 };
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index eb8c4c378c..a266396576 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -2049,6 +2049,9 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings)
                              hdev->vqs + i,
                              hdev->vq_index + i);
     }
+    if (hdev->vhost_ops->vhost_reset_status) {
+        hdev->vhost_ops->vhost_reset_status(hdev);
+    }
 
     if (vhost_dev_has_iommu(hdev)) {
         if (hdev->vhost_ops->vhost_set_iotlb_callback) {
-- 
2.31.1

[PATCH v5 08/14] vdpa: add vdpa net migration state notifier

[Eugenio Pérez]

This allows net to restart the device backend to configure SVQ on it.

Ideally, these changes should not be net specific and they could be done
in:
* vhost_vdpa_set_features (with VHOST_F_LOG_ALL)
* vhost_vdpa_set_vring_addr (with .enable_log)
* vhost_vdpa_set_log_base.

However, the vdpa net backend is the one with enough knowledge to
configure everything because of some reasons:
* Queues might need to be shadowed or not depending on its kind (control
  vs data).
* Queues need to share the same map translations (iova tree).

Also, there are other problems that may have solutions but complicates
the implementation at this stage:
* We're basically duplicating vhost_dev_start and vhost_dev_stop, and
  they could go out of sync.  If we want to reuse them, we need a way to
  skip some function calls to avoid recursiveness (either vhost_ops ->
  vhost_set_features, vhost_set_vring_addr, ...).
* We need to traverse all vhost_dev of a given net device twice: one to
  stop and get the vq state and another one after the reset to
  configure properties like address, fd, etc.

Because of that it is cleaner to restart the whole net backend and
configure again as expected, similar to how vhost-kernel moves between
userspace and passthrough.

If more kinds of devices need dynamic switching to SVQ we can:
* Create a callback struct like VhostOps and move most of the code
  there.  VhostOps cannot be reused since all vdpa backend share them,
  and to personalize just for networking would be too heavy.
* Add a parent struct or link all the vhost_vdpa or vhost_dev structs so
  we can traverse them.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
v5:
* Expand patch message with latest conversation in mail thread.

v4:
* Delete duplication of set shadow_data and shadow_vqs_enabled moving it
  to data / cvq net start functions.

v3:
* Check for migration state at vdpa device start to enable SVQ in data
  vqs.

v1 from RFC:
* Add TODO to use the resume operation in the future.
* Use migration_in_setup and migration_has_failed instead of a
  complicated switch case.
---
 net/vhost-vdpa.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 69 insertions(+), 3 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index d195f48776..167b43679d 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -26,12 +26,15 @@
 #include <err.h>
 #include "standard-headers/linux/virtio_net.h"
 #include "monitor/monitor.h"
+#include "migration/migration.h"
+#include "migration/misc.h"
 #include "hw/virtio/vhost.h"
 
 /* Todo:need to add the multiqueue support here */
 typedef struct VhostVDPAState {
     NetClientState nc;
     struct vhost_vdpa vhost_vdpa;
+    Notifier migration_state;
     VHostNetState *vhost_net;
 
     /* Control commands shadow buffers */
@@ -239,10 +242,59 @@ static VhostVDPAState *vhost_vdpa_net_first_nc_vdpa(VhostVDPAState *s)
     return DO_UPCAST(VhostVDPAState, nc, nc0);
 }
 
+static void vhost_vdpa_net_log_global_enable(VhostVDPAState *s, bool enable)
+{
+    struct vhost_vdpa *v = &s->vhost_vdpa;
+    VirtIONet *n;
+    VirtIODevice *vdev;
+    int data_queue_pairs, cvq, r;
+
+    /* We are only called on the first data vqs and only if x-svq is not set */
+    if (s->vhost_vdpa.shadow_vqs_enabled == enable) {
+        return;
+    }
+
+    vdev = v->dev->vdev;
+    n = VIRTIO_NET(vdev);
+    if (!n->vhost_started) {
+        return;
+    }
+
+    data_queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
+    cvq = virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ) ?
+                                  n->max_ncs - n->max_queue_pairs : 0;
+    /*
+     * TODO: vhost_net_stop does suspend, get_base and reset. We can be smarter
+     * in the future and resume the device if read-only operations between
+     * suspend and reset goes wrong.
+     */
+    vhost_net_stop(vdev, n->nic->ncs, data_queue_pairs, cvq);
+
+    /* Start will check migration setup_or_active to configure or not SVQ */
+    r = vhost_net_start(vdev, n->nic->ncs, data_queue_pairs, cvq);
+    if (unlikely(r < 0)) {
+        error_report("unable to start vhost net: %s(%d)", g_strerror(-r), -r);
+    }
+}
+
+static void vdpa_net_migration_state_notifier(Notifier *notifier, void *data)
+{
+    MigrationState *migration = data;
+    VhostVDPAState *s = container_of(notifier, VhostVDPAState,
+                                     migration_state);
+
+    if (migration_in_setup(migration)) {
+        vhost_vdpa_net_log_global_enable(s, true);
+    } else if (migration_has_failed(migration)) {
+        vhost_vdpa_net_log_global_enable(s, false);
+    }
+}
+
 static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
 {
     struct vhost_vdpa *v = &s->vhost_vdpa;
 
+    add_migration_state_change_notifier(&s->migration_state);
     if (v->shadow_vqs_enabled) {
         v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
                                            v->iova_range.last);
@@ -256,6 +308,15 @@ static int vhost_vdpa_net_data_start(NetClientState *nc)
 
     assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
 
+    if (s->always_svq ||
+        migration_is_setup_or_active(migrate_get_current()->state)) {
+        v->shadow_vqs_enabled = true;
+        v->shadow_data = true;
+    } else {
+        v->shadow_vqs_enabled = false;
+        v->shadow_data = false;
+    }
+
     if (v->index == 0) {
         vhost_vdpa_net_data_start_first(s);
         return 0;
@@ -276,6 +337,10 @@ static void vhost_vdpa_net_client_stop(NetClientState *nc)
 
     assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
 
+    if (s->vhost_vdpa.index == 0) {
+        remove_migration_state_change_notifier(&s->migration_state);
+    }
+
     dev = s->vhost_vdpa.dev;
     if (dev->vq_index + dev->nvqs == dev->vq_index_end) {
         g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
@@ -412,11 +477,12 @@ static int vhost_vdpa_net_cvq_start(NetClientState *nc)
     s = DO_UPCAST(VhostVDPAState, nc, nc);
     v = &s->vhost_vdpa;
 
-    v->shadow_data = s->always_svq;
+    s0 = vhost_vdpa_net_first_nc_vdpa(s);
+    v->shadow_data = s0->vhost_vdpa.shadow_vqs_enabled;
     v->shadow_vqs_enabled = s->always_svq;
     s->vhost_vdpa.address_space_id = VHOST_VDPA_GUEST_PA_ASID;
 
-    if (s->always_svq) {
+    if (s->vhost_vdpa.shadow_data) {
         /* SVQ is already configured for all virtqueues */
         goto out;
     }
@@ -473,7 +539,6 @@ out:
         return 0;
     }
 
-    s0 = vhost_vdpa_net_first_nc_vdpa(s);
     if (s0->vhost_vdpa.iova_tree) {
         /*
          * SVQ is already configured for all virtqueues.  Reuse IOVA tree for
@@ -749,6 +814,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
     s->vhost_vdpa.device_fd = vdpa_device_fd;
     s->vhost_vdpa.index = queue_pair_index;
     s->always_svq = svq;
+    s->migration_state.notify = vdpa_net_migration_state_notifier;
     s->vhost_vdpa.shadow_vqs_enabled = svq;
     s->vhost_vdpa.iova_range = iova_range;
     s->vhost_vdpa.shadow_data = svq;
-- 
2.31.1

[PATCH v5 09/14] vdpa: disable RAM block discard only for the first device

[Eugenio Pérez]

Although it does not make a big difference, its more correct and
simplifies the cleanup path in subsequent patches.

Move ram_block_discard_disable(false) call to the top of
vhost_vdpa_cleanup because:
* We cannot use vhost_vdpa_first_dev after dev->opaque = NULL
  assignment.
* Improve the stack order in cleanup: since it is the last action taken
  in init, it should be the first at cleanup.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index c9a82ce5e0..49afa59261 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -431,16 +431,6 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
     trace_vhost_vdpa_init(dev, opaque);
     int ret;
 
-    /*
-     * Similar to VFIO, we end up pinning all guest memory and have to
-     * disable discarding of RAM.
-     */
-    ret = ram_block_discard_disable(true);
-    if (ret) {
-        error_report("Cannot set discarding of RAM broken");
-        return ret;
-    }
-
     v = opaque;
     v->dev = dev;
     dev->opaque =  opaque ;
@@ -452,6 +442,16 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
         return 0;
     }
 
+    /*
+     * Similar to VFIO, we end up pinning all guest memory and have to
+     * disable discarding of RAM.
+     */
+    ret = ram_block_discard_disable(true);
+    if (ret) {
+        error_report("Cannot set discarding of RAM broken");
+        return ret;
+    }
+
     vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
                                VIRTIO_CONFIG_S_DRIVER);
 
@@ -577,12 +577,15 @@ static int vhost_vdpa_cleanup(struct vhost_dev *dev)
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
     v = dev->opaque;
     trace_vhost_vdpa_cleanup(dev, v);
+    if (vhost_vdpa_first_dev(dev)) {
+        ram_block_discard_disable(false);
+    }
+
     vhost_vdpa_host_notifiers_uninit(dev, dev->nvqs);
     memory_listener_unregister(&v->listener);
     vhost_vdpa_svq_cleanup(dev);
 
     dev->opaque = NULL;
-    ram_block_discard_disable(false);
 
     return 0;
 }
-- 
2.31.1

[PATCH v5 10/14] vdpa net: block migration if the device has CVQ

[Eugenio Pérez]

Devices with CVQ need to migrate state beyond vq state.  Leaving this to
future series.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
v5: Fix comment (s/v/s->vhost_vdpa/).
v3: Migration blocker is registered in vhost_dev.
---
 include/hw/virtio/vhost-vdpa.h | 1 +
 hw/virtio/vhost-vdpa.c         | 1 +
 net/vhost-vdpa.c               | 9 +++++++++
 3 files changed, 11 insertions(+)

diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index 4a7d396674..c278a2a8de 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -50,6 +50,7 @@ typedef struct vhost_vdpa {
     const VhostShadowVirtqueueOps *shadow_vq_ops;
     void *shadow_vq_ops_opaque;
     struct vhost_dev *dev;
+    Error *migration_blocker;
     VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX];
 } VhostVDPA;
 
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 49afa59261..e9167977d5 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -438,6 +438,7 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
     v->msg_type = VHOST_IOTLB_MSG_V2;
     vhost_vdpa_init_svq(dev, v);
 
+    error_propagate(&dev->migration_blocker, v->migration_blocker);
     if (!vhost_vdpa_first_dev(dev)) {
         return 0;
     }
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 167b43679d..533ba54317 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -828,6 +828,15 @@ 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;
+
+        /*
+         * TODO: We cannot migrate devices with CVQ as there is no way to set
+         * the device state (MAC, MQ, etc) before starting the datapath.
+         *
+         * Migration blocker ownership now belongs to s->vhost_vdpa.
+         */
+        error_setg(&s->vhost_vdpa.migration_blocker,
+                   "net vdpa cannot migrate with CVQ feature");
     }
     ret = vhost_vdpa_add(nc, (void *)&s->vhost_vdpa, queue_pair_index, nvqs);
     if (ret) {
-- 
2.31.1

[PATCH v5 11/14] vdpa: block migration if device has unsupported features

[Eugenio Pérez]

A vdpa net device must initialize with SVQ in order to be migratable at
this moment, and initialization code verifies some conditions.  If the
device is not initialized with the x-svq parameter, it will not expose
_F_LOG so the vhost subsystem will block VM migration from its
initialization.

Next patches change this, so we need to verify migration conditions
differently.

QEMU only supports a subset of net features in SVQ, and it cannot
migrate state that cannot track or restore in the destination.  Add a
migration blocker if the device offers an unsupported feature.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
v3: add migration blocker properly so vhost_dev can handle it.
---
 net/vhost-vdpa.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 533ba54317..1089c35959 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -795,7 +795,8 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
                                        int nvqs,
                                        bool is_datapath,
                                        bool svq,
-                                       struct vhost_vdpa_iova_range iova_range)
+                                       struct vhost_vdpa_iova_range iova_range,
+                                       uint64_t features)
 {
     NetClientState *nc = NULL;
     VhostVDPAState *s;
@@ -818,7 +819,10 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
     s->vhost_vdpa.shadow_vqs_enabled = svq;
     s->vhost_vdpa.iova_range = iova_range;
     s->vhost_vdpa.shadow_data = svq;
-    if (!is_datapath) {
+    if (queue_pair_index == 0) {
+        vhost_vdpa_net_valid_svq_features(features,
+                                          &s->vhost_vdpa.migration_blocker);
+    } else if (!is_datapath) {
         s->cvq_cmd_out_buffer = qemu_memalign(qemu_real_host_page_size(),
                                             vhost_vdpa_net_cvq_cmd_page_len());
         memset(s->cvq_cmd_out_buffer, 0, vhost_vdpa_net_cvq_cmd_page_len());
@@ -956,7 +960,7 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
     for (i = 0; i < queue_pairs; i++) {
         ncs[i] = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
                                      vdpa_device_fd, i, 2, true, opts->x_svq,
-                                     iova_range);
+                                     iova_range, features);
         if (!ncs[i])
             goto err;
     }
@@ -964,7 +968,7 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
     if (has_cvq) {
         nc = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
                                  vdpa_device_fd, i, 1, false,
-                                 opts->x_svq, iova_range);
+                                 opts->x_svq, iova_range, features);
         if (!nc)
             goto err;
     }
-- 
2.31.1

[PATCH v5 12/14] vdpa: block migration if SVQ does not admit a feature

[Eugenio Pérez]

Next patches enable devices to be migrated even if vdpa netdev has not
been started with x-svq. However, not all devices are migratable, so we
need to block migration if we detect that.

Block migration if we detect the device expose a feature SVQ does not
know how to work with.

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

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index e9167977d5..48ffb67a34 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -443,6 +443,21 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
         return 0;
     }
 
+    /*
+     * If dev->shadow_vqs_enabled at initialization that means the device has
+     * been started with x-svq=on, so don't block migration
+     */
+    if (dev->migration_blocker == NULL && !v->shadow_vqs_enabled) {
+        /* We don't have dev->features yet */
+        uint64_t features;
+        ret = vhost_vdpa_get_dev_features(dev, &features);
+        if (unlikely(ret)) {
+            error_setg_errno(errp, -ret, "Could not get device features");
+            return ret;
+        }
+        vhost_svq_valid_features(features, &dev->migration_blocker);
+    }
+
     /*
      * Similar to VFIO, we end up pinning all guest memory and have to
      * disable discarding of RAM.
-- 
2.31.1

[PATCH v5 13/14] vdpa net: allow VHOST_F_LOG_ALL

[Eugenio Pérez]

Since some actions move to the start function instead of init, the
device features may not be the parent vdpa device's, but the one
returned by vhost backend.  If transition to SVQ is supported, the vhost
backend will return _F_LOG_ALL to signal the device is migratable.

Add VHOST_F_LOG_ALL.  HW dirty page tracking can be added on top of this
change if the device supports it in the future.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 net/vhost-vdpa.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 1089c35959..99904a0da7 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -101,6 +101,8 @@ static const uint64_t vdpa_svq_device_features =
     BIT_ULL(VIRTIO_NET_F_MQ) |
     BIT_ULL(VIRTIO_F_ANY_LAYOUT) |
     BIT_ULL(VIRTIO_NET_F_CTRL_MAC_ADDR) |
+    /* VHOST_F_LOG_ALL is exposed by SVQ */
+    BIT_ULL(VHOST_F_LOG_ALL) |
     BIT_ULL(VIRTIO_NET_F_RSC_EXT) |
     BIT_ULL(VIRTIO_NET_F_STANDBY);
 
-- 
2.31.1

[PATCH v5 14/14] vdpa: return VHOST_F_LOG_ALL in vhost-vdpa devices

[Eugenio Pérez]

vhost-vdpa devices can return this feature now that blockers have been
set in case some features are not met.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 48ffb67a34..bc6bad23d5 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1294,10 +1294,9 @@ static int vhost_vdpa_set_vring_call(struct vhost_dev *dev,
 static int vhost_vdpa_get_features(struct vhost_dev *dev,
                                      uint64_t *features)
 {
-    struct vhost_vdpa *v = dev->opaque;
     int ret = vhost_vdpa_get_dev_features(dev, features);
 
-    if (ret == 0 && v->shadow_vqs_enabled) {
+    if (ret == 0) {
         /* Add SVQ logging capabilities */
         *features |= BIT_ULL(VHOST_F_LOG_ALL);
     }
-- 
2.31.1

Re: [PATCH v5 00/14] Dynamically switch to vhost shadow virtqueues at vdpa net migration

[Lei Yang]

[-- Attachment #1: Type: text/plain, Size: 5696 bytes --]

QE tested this series's V5 again. Creating two vdpa_sim device, and boot
two VMs without shadow virtqueues. The migration was successful and
everything worked fine.

Tested-by: Lei Yang <leiyang@redhat.com>

Eugenio Pérez <eperezma@redhat.com> 于2023年3月4日周六 01:24写道：

> It's possible to migrate vdpa net devices if they are shadowed from the
> start.  But to always shadow the dataplane is to effectively break its host
> passthrough, so its not efficient in vDPA scenarios.
>
> This series enables dynamically switching to shadow mode only at
> migration time.  This allows full data virtqueues passthrough all the
> time qemu is not migrating.
>
> In this series only net devices with no CVQ are migratable.  CVQ adds
> additional state that would make the series bigger and still had some
> controversy on previous RFC, so let's split it.
>
> Successfully tested with vdpa_sim_net with patch [1] applied and with the
> qemu
> emulated device with vp_vdpa with some restrictions:
> * No CVQ. No feature that didn't work with SVQ previously (packed, ...)
> * VIRTIO_RING_F_STATE patches implementing [2].
>
> Previous versions were tested by many vendors. Not carrying Tested-by
> because
> of code changes, so re-testing would be appreciated.
>
> A ready to clone tag named vdpa.d/stop-nocvq-v5 with this version of the
> series
> is available at https://gitlab.com/eperezmartin/qemu-kvm.git, with the
> commit
> 863d54ff00c558ffe54ed2c7ee148ab7f89d4864 ("vdpa: return VHOST_F_LOG_ALL in
> vhost-vdpa devices").
>
> Comments are welcome.
>
> v5:
> - Reverse SUSPEND polarity check, as qemu was never suspending devices with
>   suspend capability.
> - Reorder suspend patch so it comes before the reset reorder after
>   get_vring_base.
> - Remove patch to stop SVQ at vdpa stop, already present in staging
>
> v4:
> - Recover used_idx from guest's vring if device cannot suspend.
> - Fix starting device in the middle of a migration.  Removed some
>   duplication in setting / clearing enable_shadow_vqs and shadow_data
>   members of vhost_vdpa.
> - Fix (again) "Check for SUSPEND in vhost_dev.backend_cap, as
>   .backend_features is empty at the check moment.". It was reverted by
>   mistake in v3.
> - Fix memory leak of iova tree.
> - Properly rewind SVQ as in flight descriptors were still being accounted
>   in vq base.
> - Expand documentation.
>
> v3:
> - Start datapatch in SVQ in device started while migrating.
> - Properly register migration blockers if device present unsupported
> features.
> - Fix race condition because of not stopping the SVQ until device cleanup.
> - Explain purpose of iova tree in the first patch message.
> - s/dynamycally/dynamically/ in cover letter.
> - at
> lore.kernel.org/qemu-devel/20230215173850.298832-14-eperezma@redhat.com
>
> v2:
> - Check for SUSPEND in vhost_dev.backend_cap, as .backend_features is
> empty at
>   the check moment.
> - at
> https://lore.kernel.org/all/20230208094253.702672-12-eperezma@redhat.com/T/
>
> v1:
> - Omit all code working with CVQ and block migration if the device supports
>   CVQ.
> - Remove spurious kick.
> - Move all possible checks for migration to vhost-vdpa instead of the net
>   backend. Move them to init code from start code.
> - Suspend on vhost_vdpa_dev_start(false) instead of in vhost-vdpa net
> backend.
> - Properly split suspend after geting base and adding of status_reset
> patches.
> - Add possible TODOs to points where this series can improve in the future.
> - Check the state of migration using migration_in_setup and
>   migration_has_failed instead of checking all the possible migration
> status in
>   a switch.
> - Add TODO with possible low hand fruit using RESUME ops.
> - Always offer _F_LOG from virtio/vhost-vdpa and let migration blockers do
>   their thing instead of adding a variable.
> - RFC v2 at
> https://lists.gnu.org/archive/html/qemu-devel/2023-01/msg02574.html
>
> RFC v2:
> - Use a migration listener instead of a memory listener to know when
>   the migration starts.
> - Add stuff not picked with ASID patches, like enable rings after
>   driver_ok
> - Add rewinding on the migration src, not in dst
> - RFC v1 at
> https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg01664.html
>
> [1]
> https://lore.kernel.org/lkml/20230203142501.300125-1-eperezma@redhat.com/T/
> [2]
> https://lists.oasis-open.org/archives/virtio-comment/202103/msg00036.html
>
> Eugenio Pérez (14):
>   vdpa net: move iova tree creation from init to start
>   vdpa: Remember last call fd set
>   vdpa: Negotiate _F_SUSPEND feature
>   vdpa: rewind at get_base, not set_base
>   vdpa: add vhost_vdpa->suspended parameter
>   vdpa: add vhost_vdpa_suspend
>   vdpa: move vhost reset after get vring base
>   vdpa: add vdpa net migration state notifier
>   vdpa: disable RAM block discard only for the first device
>   vdpa net: block migration if the device has CVQ
>   vdpa: block migration if device has unsupported features
>   vdpa: block migration if SVQ does not admit a feature
>   vdpa net: allow VHOST_F_LOG_ALL
>   vdpa: return VHOST_F_LOG_ALL in vhost-vdpa devices
>
>  include/hw/virtio/vhost-backend.h  |   4 +
>  include/hw/virtio/vhost-vdpa.h     |   3 +
>  hw/virtio/vhost-shadow-virtqueue.c |   8 +-
>  hw/virtio/vhost-vdpa.c             | 126 ++++++++++++------
>  hw/virtio/vhost.c                  |   3 +
>  net/vhost-vdpa.c                   | 198 ++++++++++++++++++++++++-----
>  hw/virtio/trace-events             |   1 +
>  7 files changed, 272 insertions(+), 71 deletions(-)
>
> --
> 2.31.1
>
>
>

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