Re: [Qemu-devel] [PATCH v3 13/13] RFC: add explicit can_migrate to vhost_user_backend_dev_init()

[Marc-André Lureau]

Michael,

On Fri, Feb 8, 2019 at 12:34 PM Marc-André Lureau
<address@hidden> wrote:
>
> In general, there is not much support for migrating a vhost-user slave
> process. Many virtio devices however implement vmsd, and the
> vhost-user instances (as child objects) may be migrated.
>
> Since there is no other support at this point, the slave is assumed to
> be state less (outside of VM state), or using a migration method
> outside of qemu migration stream.
>
> Since this is not well specified, add a common blocker for the
> VhostUserBackend users (vhost-user-input and upcoming gpu will use
> it).
>
> RFC since I am not sure that's what Michael had in mind when
> requesting such blocker.

Could you look at that proposal?

thanks

>
> Signed-off-by: Marc-André Lureau <address@hidden>
> ---
>  include/sysemu/vhost-user-backend.h | 2 +-
>  backends/vhost-user.c               | 7 ++++++-
>  hw/input/vhost-user-input.c         | 2 +-
>  3 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/include/sysemu/vhost-user-backend.h 
> b/include/sysemu/vhost-user-backend.h
> index 60f811cae7..feb331288f 100644
> --- a/include/sysemu/vhost-user-backend.h
> +++ b/include/sysemu/vhost-user-backend.h
> @@ -53,7 +53,7 @@ struct VhostUserBackend {
>  };
>
>  int vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
> -                                unsigned nvqs, Error **errp);
> +                                unsigned nvqs, bool can_migrate, Error 
> **errp);
>  void vhost_user_backend_start(VhostUserBackend *b);
>  void vhost_user_backend_stop(VhostUserBackend *b);
>
> diff --git a/backends/vhost-user.c b/backends/vhost-user.c
> index 289dbd9e6d..7fa52d2f47 100644
> --- a/backends/vhost-user.c
> +++ b/backends/vhost-user.c
> @@ -30,7 +30,7 @@ ioeventfd_enabled(void)
>
>  int
>  vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
> -                            unsigned nvqs, Error **errp)
> +                            unsigned nvqs, bool can_migrate, Error **errp)
>  {
>      int ret;
>
> @@ -49,6 +49,11 @@ vhost_user_backend_dev_init(VhostUserBackend *b, 
> VirtIODevice *vdev,
>      b->dev.nvqs = nvqs;
>      b->dev.vqs = g_new(struct vhost_virtqueue, nvqs);
>
> +    if (!can_migrate && !b->dev.migration_blocker) {
> +        error_setg(&b->dev.migration_blocker,
> +                   "Migration disabled: vhost-user device can't migrate");
> +    }
> +
>      ret = vhost_dev_init(&b->dev, &b->vhost_user, VHOST_BACKEND_TYPE_USER, 
> 0);
>      if (ret < 0) {
>          error_setg_errno(errp, -ret, "vhost initialization failed");
> diff --git a/hw/input/vhost-user-input.c b/hw/input/vhost-user-input.c
> index 2ea1e50ab7..58b1684156 100644
> --- a/hw/input/vhost-user-input.c
> +++ b/hw/input/vhost-user-input.c
> @@ -24,7 +24,7 @@ static void vhost_input_realize(DeviceState *dev, Error 
> **errp)
>          return;
>      }
>
> -    if (vhost_user_backend_dev_init(vhi->vhost, vdev, 2, errp) == -1) {
> +    if (vhost_user_backend_dev_init(vhi->vhost, vdev, 2, false, errp) == -1) 
> {
>          return;
>      }
>
> --
> 2.20.1.519.g8feddda32c
>
>


-- 
Marc-André Lureau