Re: [Qemu-devel] [PATCH 11/12] virtio-net: migration support for multiqueue

[Michael S. Tsirkin]

On Fri, Dec 28, 2012 at 06:32:03PM +0800, Jason Wang wrote:
> This patch add migration support for multiqueue virtio-net. The version were
> bumped to 12.
> 
> Signed-off-by: Jason Wang <address@hidden>
> ---
>  hw/virtio-net.c |   45 +++++++++++++++++++++++++++++++++++----------
>  1 files changed, 35 insertions(+), 10 deletions(-)
> 
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index aaeef1b..ca4b804 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -21,7 +21,7 @@
>  #include "virtio-net.h"
>  #include "vhost_net.h"
>  
> -#define VIRTIO_NET_VM_VERSION    11
> +#define VIRTIO_NET_VM_VERSION    12

Please don't, use a subsection instead.

>  #define MAC_TABLE_ENTRIES    64
>  #define MAX_VLAN    (1 << 12)   /* Per 802.1Q definition */
> @@ -1058,16 +1058,18 @@ static void virtio_net_set_multiqueue(VirtIONet *n, 
> int multiqueue, int ctrl)
>  
>  static void virtio_net_save(QEMUFile *f, void *opaque)
>  {
> +    int i;
>      VirtIONet *n = opaque;
> -    VirtIONetQueue *q = &n->vqs[0];
>  
> -    /* At this point, backend must be stopped, otherwise
> -     * it might keep writing to memory. */
> -    assert(!q->vhost_started);
> +    for (i = 0; i < n->max_queues; i++) {
> +        /* At this point, backend must be stopped, otherwise
> +         * it might keep writing to memory. */
> +        assert(!n->vqs[i].vhost_started);
> +    }
>      virtio_save(&n->vdev, f);
>  
>      qemu_put_buffer(f, n->mac, ETH_ALEN);
> -    qemu_put_be32(f, q->tx_waiting);
> +    qemu_put_be32(f, n->vqs[0].tx_waiting);
>      qemu_put_be32(f, n->mergeable_rx_bufs);
>      qemu_put_be16(f, n->status);
>      qemu_put_byte(f, n->promisc);
> @@ -1083,13 +1085,17 @@ static void virtio_net_save(QEMUFile *f, void *opaque)
>      qemu_put_byte(f, n->nouni);
>      qemu_put_byte(f, n->nobcast);
>      qemu_put_byte(f, n->has_ufo);
> +    qemu_put_be16(f, n->max_queues);

Above is specified by user so seems unnecessary in the migration stream.

Below should only be put if relevant: check host feature bit
set and/or max_queues > 1.

> +    qemu_put_be16(f, n->curr_queues);
> +    for (i = 1; i < n->curr_queues; i++) {
> +        qemu_put_be32(f, n->vqs[i].tx_waiting);
> +    }
>  }
>  
>  static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
>  {
>      VirtIONet *n = opaque;
> -    VirtIONetQueue *q = &n->vqs[0];
> -    int ret, i;
> +    int ret, i, link_down;
>  
>      if (version_id < 2 || version_id > VIRTIO_NET_VM_VERSION)
>          return -EINVAL;
> @@ -1100,7 +1106,7 @@ static int virtio_net_load(QEMUFile *f, void *opaque, 
> int version_id)
>      }
>  
>      qemu_get_buffer(f, n->mac, ETH_ALEN);
> -    q->tx_waiting = qemu_get_be32(f);
> +    n->vqs[0].tx_waiting = qemu_get_be32(f);
>  
>      virtio_net_set_mrg_rx_bufs(n, qemu_get_be32(f));
>  
> @@ -1170,6 +1176,22 @@ static int virtio_net_load(QEMUFile *f, void *opaque, 
> int version_id)
>          }
>      }
>  
> +    if (version_id >= 12) {
> +        if (n->max_queues != qemu_get_be16(f)) {
> +            error_report("virtio-net: different max_queues ");
> +            return -1;
> +        }
> +
> +        n->curr_queues = qemu_get_be16(f);
> +        for (i = 1; i < n->curr_queues; i++) {
> +            n->vqs[i].tx_waiting = qemu_get_be32(f);
> +        }
> +    }
> +
> +    virtio_net_set_queues(n);
> +    /* Must do this again, since we may have more than one active queues. */

s/queues/queue/

Also I didn't understand why it's here.
It seems that virtio has vm running callback,
and that will invoke virtio_net_set_status after vm load.
No?


> +    virtio_net_set_status(&n->vdev, n->status);
> +
>      /* Find the first multicast entry in the saved MAC filter */
>      for (i = 0; i < n->mac_table.in_use; i++) {
>          if (n->mac_table.macs[i * ETH_ALEN] & 1) {
> @@ -1180,7 +1202,10 @@ static int virtio_net_load(QEMUFile *f, void *opaque, 
> int version_id)
>  
>      /* nc.link_down can't be migrated, so infer link_down according
>       * to link status bit in n->status */
> -    qemu_get_queue(n->nic)->link_down = (n->status & VIRTIO_NET_S_LINK_UP) 
> == 0;
> +    link_down = (n->status & VIRTIO_NET_S_LINK_UP) == 0;
> +    for (i = 0; i < n->max_queues; i++) {
> +        qemu_get_subqueue(n->nic, i)->link_down = link_down;
> +    }
>  
>      return 0;
>  }
> -- 
> 1.7.1