Re: [Qemu-devel] [PATCH v3 2/2] vhost user: Add RARP injection for legacy guest

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 10, 2015 at 03:43:03PM +0200, Thibaut Collet wrote:
> In case of live migration with legacy guest (without VIRTIO_NET_F_GUEST_ANNOUNCE)
> a message is added between QEMU and the vhost client/backend.
> This message provides the RARP content, prepared by QEMU, to the vhost
> client/backend.
> The vhost client/backend is responsible to send the RARP.
> 
> Signed-off-by: Thibaut Collet <thibaut.collet@6wind.com>
> ---
>  docs/specs/vhost-user.txt   |   16 ++++++++++++++++
>  hw/net/vhost_net.c          |    8 ++++++++
>  hw/virtio/vhost-user.c      |   11 ++++++++++-
>  linux-headers/linux/vhost.h |    9 +++++++++
>  4 files changed, 43 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index 2c8e934..ef5d475 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -97,6 +97,7 @@ typedef struct VhostUserMsg {
>          uint64_t u64;
>          struct vhost_vring_state state;
>          struct vhost_vring_addr addr;
> +        struct vhost_inject_rarp rarp;
>          VhostUserMemory memory;
>      };
>  } QEMU_PACKED VhostUserMsg;
> @@ -132,6 +133,12 @@ Multi queue support
>  The protocol supports multiple queues by setting all index fields in the sent
>  messages to a properly calculated value.
>  
> +Live migration support
> +----------------------
> +The protocol supports live migration. GARP from the migrated guest is done
> +through the VIRTIO_NET_F_GUEST_ANNOUNCE mechanism for guest that supports it or
> +through RARP.
> +
>  Message types
>  -------------
>  
> @@ -269,3 +276,12 @@ Message types
>        Bits (0-7) of the payload contain the vring index. Bit 8 is the
>        invalid FD flag. This flag is set when there is no file descriptor
>        in the ancillary data.
> +
> + * VHOST_USER_NET_INJECT_RARP
> +
> +      Id: 15
> +      Master payload: rarp content
> +
> +      Provide the RARP message to send to the guest after a live migration. This
> +      message is sent only for guest that does not support
> +      VIRTIO_NET_F_GUEST_ANNOUNCE.

I don't see why this is needed.
Can't backend simply send rarp itself?
Why do we need to involve QEMU?



> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index 4a42325..f66d48d 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -369,10 +369,18 @@ void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs,
>  
>  void vhost_net_inject_rarp(struct vhost_net *net, const uint8_t *buf, size_t size)
>  {
> +    struct vhost_inject_rarp inject_rarp;
> +    memcpy(&inject_rarp.rarp, buf, size);
> +
>      if ((net->dev.acked_features & (1 << VIRTIO_NET_F_GUEST_ANNOUNCE)) == 0) {
> +        const VhostOps *vhost_ops = net->dev.vhost_ops;
> +        int r;
> +
>          fprintf(stderr,
>                  "Warning: Guest with no VIRTIO_NET_F_GUEST_ANNOUNCE support. RARP must be sent by vhost-user backend\n");
>          fflush(stderr);
> +        r = vhost_ops->vhost_call(&net->dev, VHOST_NET_INJECT_RARP, &inject_rarp);
> +        assert(r >= 0);
>      }
>  }
>  
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index d6f2163..2e752ab 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -41,6 +41,7 @@ typedef enum VhostUserRequest {
>      VHOST_USER_SET_VRING_KICK = 12,
>      VHOST_USER_SET_VRING_CALL = 13,
>      VHOST_USER_SET_VRING_ERR = 14,
> +    VHOST_USER_NET_INJECT_RARP = 15,
>      VHOST_USER_MAX
>  } VhostUserRequest;
>  
> @@ -70,6 +71,7 @@ typedef struct VhostUserMsg {
>          uint64_t u64;
>          struct vhost_vring_state state;
>          struct vhost_vring_addr addr;
> +        struct vhost_inject_rarp rarp;
>          VhostUserMemory memory;
>      };
>  } QEMU_PACKED VhostUserMsg;
> @@ -104,7 +106,8 @@ static unsigned long int ioctl_to_vhost_user_request[VHOST_USER_MAX] = {
>      VHOST_GET_VRING_BASE,   /* VHOST_USER_GET_VRING_BASE */
>      VHOST_SET_VRING_KICK,   /* VHOST_USER_SET_VRING_KICK */
>      VHOST_SET_VRING_CALL,   /* VHOST_USER_SET_VRING_CALL */
> -    VHOST_SET_VRING_ERR     /* VHOST_USER_SET_VRING_ERR */
> +    VHOST_SET_VRING_ERR,    /* VHOST_USER_SET_VRING_ERR */
> +    VHOST_NET_INJECT_RARP   /* VHOST_USER_NET_INJECT_RARP */
>  };
>  
>  static VhostUserRequest vhost_user_request_translate(unsigned long int request)
> @@ -287,6 +290,12 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
>              msg.u64 |= VHOST_USER_VRING_NOFD_MASK;
>          }
>          break;
> +
> +    case VHOST_NET_INJECT_RARP:
> +        memcpy(&msg.rarp, arg, sizeof(struct vhost_inject_rarp));
> +        msg.size = sizeof(struct vhost_inject_rarp);
> +        break;
> +
>      default:
>          error_report("vhost-user trying to send unhandled ioctl");
>          return -1;
> diff --git a/linux-headers/linux/vhost.h b/linux-headers/linux/vhost.h
> index c656f61..1920134 100644
> --- a/linux-headers/linux/vhost.h
> +++ b/linux-headers/linux/vhost.h
> @@ -63,6 +63,10 @@ struct vhost_memory {
>  	struct vhost_memory_region regions[0];
>  };
>  
> +struct vhost_inject_rarp {
> +	__u8 rarp[60];
> +};
> +
>  /* ioctls */
>  
>  #define VHOST_VIRTIO 0xAF
> @@ -121,6 +125,11 @@ struct vhost_memory {
>   * device.  This can be used to stop the ring (e.g. for migration). */
>  #define VHOST_NET_SET_BACKEND _IOW(VHOST_VIRTIO, 0x30, struct vhost_vring_file)
>  
> +/* Inject a RARP in case of live migration for guest that does not support
> + * VIRTIO_NET_F_GUEST_ANNOUNCE */
> +#define VHOST_NET_INJECT_RARP _IOW(VHOST_VIRTIO, 0x31, struct vhost_inject_rarp)
> +
> +
>  /* Feature bits */
>  /* Log all write descriptors. Can be changed while device is active. */
>  #define VHOST_F_LOG_ALL 26
> -- 
> 1.7.10.4