On Thu, Jul 02, 2015 at 01:39:16PM +0100, Stefan Hajnoczi wrote:
> On Tue, Jun 30, 2015 at 10:42:37AM +0800, Fam Zheng wrote:
> > This is necessary because once we return false from .can_receive, we
> > need to flush the queue when the .can_receive conditions become true
> > again, (for example when more buffer is available).
> >
> > We can rely on net_rx_packet (which checks the same conditions) to drop
> > the packet if the device is not ready, so drop net_xen_info.can_receive.
>
> This patch changes behavior:
>
> Previously can_receive() false meant packets are queued.
>
> Now those same conditions result in net_rx_packet() returning -1, so
> packets are discarded.
>
> In order to keep the spirit of the queuing mechanism - where we tell a
> sender to hold off until more rx buffers become available - I think the
> following line in net_rx_packet() needs to be changed:
>
> if (rc == rp || RING_REQUEST_CONS_OVERFLOW(&netdev->rx_ring, rc)) {
> xen_be_printf(&netdev->xendev, 2, "no buffer, drop packet\n");
> return -1; <-- this should be changed to return 0
> }
>
> That change assumes that net_event()'s flush is always called when the
> rx ring gets more free space.
>
> Any thoughts from Xen folks?Ping?
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