[PATCH v3 00/14] Dynamically switch to vhost shadow virtqueues at vdpa net migration

[PATCH v3 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].
* Expose _F_SUSPEND, but ignore it and suspend on ring state fetch like
  DPDK.

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

Comments are welcome.

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.

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: stop svq at vhost_vdpa_dev_start(false)
  vdpa: Negotiate _F_SUSPEND feature
  vdpa: add vhost_vdpa_suspend
  vdpa: move vhost reset after get vring base
  vdpa: rewind at get_base, not set_base
  vdpa net: allow VHOST_F_LOG_ALL
  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 dev does not have _F_SUSPEND
  vdpa: block migration if SVQ does not admit a feature
  vdpa: return VHOST_F_LOG_ALL in vhost-vdpa devices

 include/hw/virtio/vhost-backend.h |   4 +
 include/hw/virtio/vhost-vdpa.h    |   1 +
 hw/virtio/vhost-vdpa.c            | 130 +++++++++++++++-----
 hw/virtio/vhost.c                 |   3 +
 net/vhost-vdpa.c                  | 195 +++++++++++++++++++++++++-----
 hw/virtio/trace-events            |   1 +
 6 files changed, 274 insertions(+), 60 deletions(-)

-- 
2.31.1

[PATCH v3 01/14] vdpa net: move iova tree creation from init to start

[Eugenio Pérez]

The iova_tree is used to track the memory assotiation between SVQ IOVA
and qemu virtual addresses. Only create iova_tree if and when it is
needed.

The cleanup keeps being responsible of 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>
---
 net/vhost-vdpa.c | 99 ++++++++++++++++++++++++++++++++++--------------
 1 file changed, 71 insertions(+), 28 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index de5ed8ff22..a9e6c8f28e 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 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;
@@ -425,6 +475,15 @@ out:
         return 0;
     }
 
+    s0 = vhost_vdpa_net_first_nc_vdpa(s);
+    if (s0->vhost_vdpa.iova_tree) {
+        /* SVQ is already configured for all virtqueues */
+        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 +508,9 @@ 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 +720,7 @@ 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 +742,6 @@ 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 +811,6 @@ 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 +862,8 @@ 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 +871,7 @@ 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 +879,11 @@ 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 +893,6 @@ err:
         }
     }
 
-err_svq:
     qemu_close(vdpa_device_fd);
 
     return -1;
-- 
2.31.1

[PATCH v3 02/14] vdpa: stop svq at vhost_vdpa_dev_start(false)

[Eugenio Pérez]

It used to be done at vhost_vdpa_svq_cleanup, since a device couldn't
switch to SVQ mode dynamically.  Now that we need to fetch the state and
trust SVQ will not modify guest's used_idx at migration, stop
effectively SVQ at suspend time, as a real device would do.

Leaving old vhost_svq_stop call at vhost_vdpa_svq_cleanup, as its
supported to call it many times and it follows other operations that are
called redundantly there too:
* vhost_vdpa_host_notifiers_uninit
* memory_listener_unregister

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
v3: New in v3
---
 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 542e003101..300062130d 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1100,10 +1100,11 @@ static void vhost_vdpa_svqs_stop(struct vhost_dev *dev)
 
     for (unsigned i = 0; i < v->shadow_vqs->len; ++i) {
         VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs, i);
+
+        vhost_svq_stop(svq);
         vhost_vdpa_svq_unmap_rings(dev, svq);
 
         event_notifier_cleanup(&svq->hdev_kick);
-        event_notifier_cleanup(&svq->hdev_call);
     }
 }
 
-- 
2.31.1

[PATCH v3 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 300062130d..1d0209d6ad 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 v3 04/14] 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>
---
 hw/virtio/vhost-vdpa.c | 19 +++++++++++++++++++
 hw/virtio/trace-events |  1 +
 2 files changed, 20 insertions(+)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 1d0209d6ad..796f38d64e 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1109,6 +1109,24 @@ 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) ||
+        !(dev->backend_features & BIT_ULL(VHOST_BACKEND_F_SUSPEND))) {
+        return;
+    }
+
+    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);
+        /* Not aborting since we're called from stop context */
+    }
+}
+
 static int vhost_vdpa_dev_start(struct vhost_dev *dev, bool started)
 {
     struct vhost_vdpa *v = dev->opaque;
@@ -1123,6 +1141,7 @@ 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 v3 05/14] 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 796f38d64e..a5cf2e7069 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1153,14 +1153,23 @@ 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,
@@ -1347,4 +1356,5 @@ 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 v3 06/14] 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>
---
 hw/virtio/vhost-vdpa.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index a5cf2e7069..d253e9dc0e 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1212,18 +1212,7 @@ 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
@@ -1242,6 +1231,19 @@ static int vhost_vdpa_get_vring_base(struct vhost_dev *dev,
     int ret;
 
     if (v->shadow_vqs_enabled) {
+        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;
+        }
+
         ring->num = virtio_queue_get_last_avail_idx(dev->vdev, ring->index);
         return 0;
     }
-- 
2.31.1

[PATCH v3 07/14] 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 a9e6c8f28e..dd686b4514 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -98,6 +98,8 @@ 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 v3 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. 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).

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.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
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 | 86 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index dd686b4514..cf9830bb02 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 */
@@ -241,10 +244,79 @@ 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;
+    NetClientState *peer;
+
+    /* 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);
+
+    peer = s->nc.peer;
+    for (int i = 0; i < data_queue_pairs + cvq; i++) {
+        VhostVDPAState *vdpa_state;
+        NetClientState *nc;
+
+        if (i < data_queue_pairs) {
+            nc = qemu_get_peer(peer, i);
+        } else {
+            nc = qemu_get_peer(peer, n->max_queue_pairs);
+        }
+
+        vdpa_state = DO_UPCAST(VhostVDPAState, nc, nc);
+        vdpa_state->vhost_vdpa.shadow_data = enable;
+
+        if (i < data_queue_pairs) {
+            /* Do not override CVQ shadow_vqs_enabled */
+            vdpa_state->vhost_vdpa.shadow_vqs_enabled = enable;
+        }
+    }
+
+    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);
@@ -258,6 +330,15 @@ 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;
@@ -278,6 +359,10 @@ 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);
@@ -741,6 +826,7 @@ 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 v3 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 d253e9dc0e..94416f520b 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 v3 10/14] vdpa net: block migration if the device has CVQ

[Eugenio Pérez]

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

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
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               | 4 ++++
 3 files changed, 6 insertions(+)

diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index 7997f09a8d..620a0f70ab 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -48,6 +48,7 @@ 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 94416f520b..52c72e7c94 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 cf9830bb02..9312329167 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -840,6 +840,10 @@ 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;
+
+        /* Migration blocker ownership now belongs to v */
+        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 v3 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 offer an unsupported feature.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
v3: add mirgation 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 9312329167..b26b611b6c 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -807,7 +807,8 @@ 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;
@@ -830,7 +831,10 @@ 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());
@@ -963,7 +967,7 @@ 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;
     }
@@ -971,7 +975,7 @@ 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 v3 12/14] vdpa: block migration if dev does not have _F_SUSPEND

[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 vhost-vdpa device migration if it does not offer _F_SUSPEND and it
has not been started with x-svq.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 52c72e7c94..3a85f9f1ed 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -443,6 +443,27 @@ 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) {
+        uint64_t backend_features;
+
+        /* We don't have dev->backend_features yet */
+        ret = vhost_vdpa_call(dev, VHOST_GET_BACKEND_FEATURES,
+                              &backend_features);
+        if (unlikely(ret)) {
+            error_setg_errno(errp, -ret, "Could not get backend features");
+            return ret;
+        }
+
+        if (!(backend_features & BIT_ULL(VHOST_BACKEND_F_SUSPEND))) {
+            error_setg(&dev->migration_blocker,
+                "vhost-vdpa backend lacks VHOST_BACKEND_F_SUSPEND feature.");
+        }
+    }
+
     /*
      * Similar to VFIO, we end up pinning all guest memory and have to
      * disable discarding of RAM.
-- 
2.31.1

[PATCH v3 13/14] 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 | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 3a85f9f1ed..9b8c22bda3 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -461,6 +461,15 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
         if (!(backend_features & BIT_ULL(VHOST_BACKEND_F_SUSPEND))) {
             error_setg(&dev->migration_blocker,
                 "vhost-vdpa backend lacks VHOST_BACKEND_F_SUSPEND feature.");
+        } else {
+            /* 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);
         }
     }
 
-- 
2.31.1

[PATCH v3 14/14] vdpa: return VHOST_F_LOG_ALL in vhost-vdpa devices

[Eugenio Pérez]

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

Expose VHOST_F_LOG_ALL only in that case.

Signed-off-by: Eugenio Pérez <eperezma@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 9b8c22bda3..33d0a4f91e 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1321,10 +1321,9 @@ 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 v3 04/14] vdpa: add vhost_vdpa_suspend

[Alvaro Karsz]

Hi,

> 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>
> ---
>  hw/virtio/vhost-vdpa.c | 19 +++++++++++++++++++
>  hw/virtio/trace-events |  1 +
>  2 files changed, 20 insertions(+)
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 1d0209d6ad..796f38d64e 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -1109,6 +1109,24 @@ 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) ||
> +        !(dev->backend_features & BIT_ULL(VHOST_BACKEND_F_SUSPEND))) {

Shouldn't it be backend_cap?

Re: [PATCH v3 04/14] vdpa: add vhost_vdpa_suspend

[Eugenio Perez Martin]

On Thu, Feb 16, 2023 at 2:48 PM Alvaro Karsz <alvaro.karsz@solid-run.com> wrote:
>
> Hi,
>
> > 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>
> > ---
> >  hw/virtio/vhost-vdpa.c | 19 +++++++++++++++++++
> >  hw/virtio/trace-events |  1 +
> >  2 files changed, 20 insertions(+)
> >
> > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > index 1d0209d6ad..796f38d64e 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -1109,6 +1109,24 @@ 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) ||
> > +        !(dev->backend_features & BIT_ULL(VHOST_BACKEND_F_SUSPEND))) {
>
> Shouldn't it be backend_cap?
>

Good catch, I reversed it by mistake.

I'll send a v4 once I fix this and other problems found. Thanks!