virtio_net: enable big packets for large MTU values

mstsirkin · mstsirkin · commit 2e123b44a3c1 · 2017-04-07T16:38:59.000+03:00
If one enables e.g. jumbo frames without mergeable
buffers, packets won't fit in 1500 byte buffers
we use. Switch to big packet mode instead.
TODO: make sizing more exact, possibly extend small
packet mode to use larger pages.

Signed-off-by: Michael S. Tsirkin &lt;mst@redhat.com&gt;
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
@@ -2367,6 +2367,10 @@ static int virtnet_probe(struct virtio_device *vdev)
 			dev->mtu = mtu;
 			dev->max_mtu = mtu;
 		}
+
+		/* TODO: size buffers correctly in this case. */
+		if (dev->mtu > ETH_DATA_LEN)
+			vi->big_packets = true;
 	}
 
 	if (vi->any_header_sg)

Original file line number	Diff line number	Diff line change
`@@ -2367,6 +2367,10 @@ static int virtnet_probe(struct virtio_device *vdev)`
`2367`	`2367`	`dev->mtu = mtu;`
`2368`	`2368`	`dev->max_mtu = mtu;`
`2369`	`2369`	`}`
	`2370`	`+`
	`2371`	`+ /* TODO: size buffers correctly in this case. */`
	`2372`	`+ if (dev->mtu > ETH_DATA_LEN)`
	`2373`	`+ vi->big_packets = true;`
`2370`	`2374`	`}`
`2371`	`2375`
`2372`	`2376`	`if (vi->any_header_sg)`