Re: [RFC v2 11/13] vdpa: add vdpa net migration state notifier

[Jason Wang]

On Fri, Jan 13, 2023 at 1:25 AM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> 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>
> ---
>  net/vhost-vdpa.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 84 insertions(+)
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 5d7ad6e4d7..f38532b1df 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -26,6 +26,8 @@
>  #include <err.h>
>  #include "standard-headers/linux/virtio_net.h"
>  #include "monitor/monitor.h"
> +#include "migration/migration.h"
> +#include "migration/misc.h"
>  #include "migration/blocker.h"
>  #include "hw/virtio/vhost.h"
>
> @@ -33,6 +35,7 @@
>  typedef struct VhostVDPAState {
>      NetClientState nc;
>      struct vhost_vdpa vhost_vdpa;
> +    Notifier migration_state;
>      Error *migration_blocker;
>      VHostNetState *vhost_net;
>
> @@ -243,10 +246,86 @@ 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;
> +    }
> +
> +    if (enable) {
> +        ioctl(v->device_fd, VHOST_VDPA_SUSPEND);

Do we need to check if the device is started or not here?

> +    }

I'm not sure I understand the reason for vhost_net_stop() after a
VHOST_VDPA_SUSPEND. It looks to me those functions are duplicated.

> +    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;
> +    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);
> +
> +    switch (migration->state) {
> +    case MIGRATION_STATUS_SETUP:
> +        vhost_vdpa_net_log_global_enable(s, true);
> +        return;
> +
> +    case MIGRATION_STATUS_CANCELLING:
> +    case MIGRATION_STATUS_CANCELLED:
> +    case MIGRATION_STATUS_FAILED:
> +        vhost_vdpa_net_log_global_enable(s, false);

Do we need to recover here?

Thanks

> +        return;
> +    };
> +}
> +
>  static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
>  {
>      struct vhost_vdpa *v = &s->vhost_vdpa;
>
> +    if (v->feature_log) {
> +        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);
> @@ -280,6 +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 && s->vhost_vdpa.feature_log) {
> +        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);
> @@ -767,6 +850,7 @@ 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
>