Re: [Qemu-devel] [PATCH for-2.7] hw/net/spapr_llan: Provide counter with dropped rx frames to the guest

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Apr 04, 2016 at 12:13:10PM +0200, Thomas Huth wrote:
> The last 8 bytes of the receive buffer list page (that has been supplied
> by the guest with the H_REGISTER_LOGICAL_LAN call) contain a counter
> for frames that have been dropped because there was no suitable receive
> buffer available. This patch introduces code to use this field to
> provide the information about dropped rx packets to the guest.
> There it can be queried with "ethtool -S eth0 | grep rx_no_buffer".
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  Note: The patch has to be applied on top of the "Delay flushing of the
>  RX queue while adding new RX buffers" patch that I sent last week
>  (otherwise there will be context conflicts with the "return"
> statements).

Applied to ppc-for-2.7, thanks.

> 
>  hw/net/spapr_llan.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/hw/net/spapr_llan.c b/hw/net/spapr_llan.c
> index d604d55..719ad29 100644
> --- a/hw/net/spapr_llan.c
> +++ b/hw/net/spapr_llan.c
> @@ -122,6 +122,21 @@ static int spapr_vlan_can_receive(NetClientState *nc)
>  }
>  
>  /**
> + * The last 8 bytes of the receive buffer list page (that has been
> + * supplied by the guest with the H_REGISTER_LOGICAL_LAN call) contain
> + * a counter for frames that have been dropped because there was no
> + * suitable receive buffer available. This function is used to increase
> + * this counter by one.
> + */
> +static void spapr_vlan_record_dropped_rx_frame(VIOsPAPRVLANDevice *dev)
> +{
> +    uint64_t cnt;
> +
> +    cnt = vio_ldq(&dev->sdev, dev->buf_list + 4096 - 8);
> +    vio_stq(&dev->sdev, dev->buf_list + 4096 - 8, cnt + 1);
> +}
> +
> +/**
>   * Get buffer descriptor from one of our receive buffer pools
>   */
>  static vlan_bd_t spapr_vlan_get_rx_bd_from_pool(VIOsPAPRVLANDevice *dev,
> @@ -206,6 +221,7 @@ static ssize_t spapr_vlan_receive(NetClientState *nc, const uint8_t *buf,
>      }
>  
>      if (!dev->rx_bufs) {
> +        spapr_vlan_record_dropped_rx_frame(dev);
>          return 0;
>      }
>  
> @@ -215,6 +231,7 @@ static ssize_t spapr_vlan_receive(NetClientState *nc, const uint8_t *buf,
>          bd = spapr_vlan_get_rx_bd_from_page(dev, size);
>      }
>      if (!bd) {
> +        spapr_vlan_record_dropped_rx_frame(dev);
>          return 0;
>      }
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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