On Fri, Nov 20, 2020 at 07:50:43PM +0100, Eugenio Pérez wrote:
> Only virtio-net honors it.
> 
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  include/hw/virtio/vhost.h |  1 +
>  hw/net/virtio-net.c       | 39 ++++++++++++++++++++++++++++-----------
>  2 files changed, 29 insertions(+), 11 deletions(-)
> 
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index 4a8bc75415..b5b7496537 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -83,6 +83,7 @@ struct vhost_dev {
>      bool started;
>      bool log_enabled;
>      uint64_t log_size;
> +    VirtIOHandleOutput sw_lm_vq_handler;

sw == software?
lm == live migration?

Maybe there is a name that is clearer. What are these virtqueues called?
Shadow vqs? Logged vqs?

Live migration is a feature that uses dirty memory logging, but other
features may use dirty memory logging too. The name should probably not
be associated with live migration.

>      Error *migration_blocker;
>      const VhostOps *vhost_ops;
>      void *opaque;
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 9179013ac4..9a69ae3598 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -2628,24 +2628,32 @@ static void virtio_net_tx_bh(void *opaque)
>      }
>  }
>  
> -static void virtio_net_add_queue(VirtIONet *n, int index)
> +static void virtio_net_add_queue(VirtIONet *n, int index,
> +                                 VirtIOHandleOutput custom_handler)
>  {

We talked about the possibility of moving this into the generic vhost
code so that devices don't need to be modified. It would be nice to hide
this feature inside vhost.