Re: [PATCH v4 09/15] vdpa: add vdpa net migration state notifier

[Jason Wang <jasowang@redhat.com>]

在 2023/2/24 23:54, Eugenio Pérez 写道:
> 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>
> ---
> 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 b89c99066a..c5512ddf10 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);
> +    }


This should work but I just realize that vhost support 
vhost_dev_set_log(), I wonder if it would be simpler to go with that way.

Using vhost_virtqueue_set_addr(, enable_log = true)?

Thanks


> +
>       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;