Re: [Qemu-devel] [PATCH for-2.4 v2] xen: Drop net_rx_ok

[Wen Congyang <wency@cn.fujitsu.com>]

On 07/28/2015 05:25 PM, Fam Zheng wrote:
> Let net_rx_packet() (which checks the same conditions) drops the packet
> if the device is not ready. Drop net_xen_info.can_receive and update the
> return value for the buffer full case.
> 
> We rely on the qemu_flush_queued_packets() in net_event() to wake up
> the peer when the buffer becomes available again.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> 
> ---
> 
> v2:
>     Fix return value of net_rx_packet to keep the semantics when ring
>     buffer is full. [Stefan]
>     Update commit message accordingly.
> ---
>  hw/net/xen_nic.c | 24 +-----------------------
>  1 file changed, 1 insertion(+), 23 deletions(-)
> 
> diff --git a/hw/net/xen_nic.c b/hw/net/xen_nic.c
> index 19ecfc4..acb7e2e 100644
> --- a/hw/net/xen_nic.c
> +++ b/hw/net/xen_nic.c
> @@ -234,27 +234,6 @@ static void net_rx_response(struct XenNetDev *netdev,
>  
>  #define NET_IP_ALIGN 2
>  
> -static int net_rx_ok(NetClientState *nc)
> -{
> -    struct XenNetDev *netdev = qemu_get_nic_opaque(nc);
> -    RING_IDX rc, rp;
> -
> -    if (netdev->xendev.be_state != XenbusStateConnected) {
> -        return 0;
> -    }
> -
> -    rc = netdev->rx_ring.req_cons;
> -    rp = netdev->rx_ring.sring->req_prod;
> -    xen_rmb();
> -
> -    if (rc == rp || RING_REQUEST_CONS_OVERFLOW(&netdev->rx_ring, rc)) {
> -        xen_be_printf(&netdev->xendev, 2, "%s: no rx buffers (%d/%d)\n",
> -                      __FUNCTION__, rc, rp);
> -        return 0;
> -    }
> -    return 1;
> -}
> -
>  static ssize_t net_rx_packet(NetClientState *nc, const uint8_t *buf, size_t size)
>  {
>      struct XenNetDev *netdev = qemu_get_nic_opaque(nc);
> @@ -272,7 +251,7 @@ static ssize_t net_rx_packet(NetClientState *nc, const uint8_t *buf, size_t size
>  
>      if (rc == rp || RING_REQUEST_CONS_OVERFLOW(&netdev->rx_ring, rc)) {
>          xen_be_printf(&netdev->xendev, 2, "no buffer, drop packet\n");

IIUC, 'return 0' means that the packet will be queued in the incoming queue. So the log should
be changed too.

Thanks
Wen Congyang

> -        return -1;
> +        return 0;
>      }
>      if (size > XC_PAGE_SIZE - NET_IP_ALIGN) {
>          xen_be_printf(&netdev->xendev, 0, "packet too big (%lu > %ld)",
> @@ -304,7 +283,6 @@ static ssize_t net_rx_packet(NetClientState *nc, const uint8_t *buf, size_t size
>  static NetClientInfo net_xen_info = {
>      .type = NET_CLIENT_OPTIONS_KIND_NIC,
>      .size = sizeof(NICState),
> -    .can_receive = net_rx_ok,
>      .receive = net_rx_packet,
>  };
>  
>