On 2020-11-16 12:55, Michael S. Tsirkin wrote:
On Mon, Nov 16, 2020 at 12:04:12PM +0100, Björn Töpel wrote:
From: Björn Töpel <bjorn.topel@xxxxxxxxx>
Add napi_id to the xdp_rxq_info structure, and make sure the XDP
socket pick up the napi_id in the Rx path. The napi_id is used to find
the corresponding NAPI structure for socket busy polling.
Acked-by: Ilias Apalodimas <ilias.apalodimas@xxxxxxxxxx>
Signed-off-by: Björn Töpel <bjorn.topel@xxxxxxxxx>
A bunch of drivers just pass in 0. could you explain when
is that ok? how bad is it if the wrong id is used?
If zero is passed, which is a non-valid NAPI_ID, busy-polling will never
be performed.
Depending on the structure of the driver, napi might or might not be
initialized (napi_id != 0) or even available. When it wasn't obvious, I
simply set it to zero.
So, short; No harm if zero, but busy-polling cannot be used in an XDP
context.
[...]
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 21b71148c532..d71fe41595b7 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1485,7 +1485,7 @@ static int virtnet_open(struct net_device *dev)
if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
schedule_delayed_work(&vi->refill, 0);
- err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i);
+ err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i, 0);
if (err < 0)
return err;
Should this be rq.napi.napi_id ?
Yes, if rq.napi.napi_id is valid here! Is it?
Cheers,
Björn
