[PATCH] virtio_net: enable big packets for large MTU values

Subsystems: networking drivers, the rest, virtio net driver

STALE3411d

3 messages, 2 authors, 2017-03-30 · open the first message on its own page

[PATCH] virtio_net: enable big packets for large MTU values

From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2017-03-29 12:38:13

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 <mst@redhat.com>
---
 drivers/net/virtio_net.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e0fb3707..9dc31dc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -2428,6 +2428,10 @@ 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)

-- 
MST

Re: [PATCH] virtio_net: enable big packets for large MTU values

From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2017-03-29 16:13:38

On Wed, Mar 29, 2017 at 03:38:09PM +0300, Michael S. Tsirkin wrote:

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 <mst@redhat.com>

Fixes: 14de9d114a82 ("virtio-net: Add initial MTU advice feature")

quoted hunk

---
 drivers/net/virtio_net.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e0fb3707..9dc31dc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -2428,6 +2428,10 @@ 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)

-- 
MST

Re: [PATCH] virtio_net: enable big packets for large MTU values

From: Jason Wang <hidden>
Date: 2017-03-30 04:03:46


On 2017年03月29日 20:38, Michael S. Tsirkin wrote:

quoted hunk

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 <mst@redhat.com>
---
  drivers/net/virtio_net.c | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e0fb3707..9dc31dc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -2428,6 +2428,10 @@ 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)

Ok, I think maybe we should fail the probe of small buffer in this case 
and decrease the max_mtu to ETH_DATA_LEN if small buffer is used (since 
user are allowed to increase the mtu).

Thanks
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

`h`	back out one level
`j`	next message in thread
`k`	previous message in thread
`l`	drill in
`Esc`	close help / fold thread tree
`?`	toggle this help