On 1/24/23 11:15, Michael S. Tsirkin wrote:
On Mon, Jan 23, 2023 at 01:00:22PM +0100, Laurent Vivier wrote:
In virtnet_probe(), if the device doesn't provide a MAC address the
driver assigns a random one.
As we modify the MAC address we need to notify the device to allow it
to update all the related information.
The problem can be seen with vDPA and mlx5_vdpa driver as it doesn't
assign a MAC address by default. The virtio_net device uses a random
MAC address (we can see it with "ip link"), but we can't ping a net
namespace from another one using the virtio-vdpa device because the
new MAC address has not been provided to the hardware.
And then what exactly happens? Does hardware drop the outgoing
or the incoming packets? Pls include in the commit log.
I don't know. There is nothing in the kernel logs.
The ping error is: "Destination Host Unreachable"
I found the problem with the mlx5 driver as in "it doesn't work when MAC address is not
set"...
Perhaps Eli can explain what happens when the MAC address is not set?
Signed-off-by: Laurent Vivier <lvivier@xxxxxxxxxx>
---
drivers/net/virtio_net.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 7723b2a49d8e..4bdc8286678b 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3800,6 +3800,8 @@ static int virtnet_probe(struct virtio_device *vdev)
eth_hw_addr_set(dev, addr);
} else {
eth_hw_addr_random(dev);
+ dev_info(&vdev->dev, "Assigned random MAC address %pM\n",
+ dev->dev_addr);
}
/* Set up our device-specific information */
@@ -3956,6 +3958,18 @@ static int virtnet_probe(struct virtio_device *vdev)
pr_debug("virtnet: registered device %s with %d RX and TX vq's\n",
dev->name, max_queue_pairs);
+ /* a random MAC address has been assigned, notify the device */
+ if (!virtio_has_feature(vdev, VIRTIO_NET_F_MAC) &&
+ virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
Maybe add a comment explaining that we don't fail probe if
VIRTIO_NET_F_CTRL_MAC_ADDR is not there because
many devices work fine without getting MAC explicitly.
OK
+ struct scatterlist sg;
+
+ sg_init_one(&sg, dev->dev_addr, dev->addr_len);
+ if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
+ VIRTIO_NET_CTRL_MAC_ADDR_SET, &sg)) {
+ dev_warn(&vdev->dev, "Failed to update MAC address.\n");
Here, I'm not sure we want to proceed. Is it useful sometimes?
I think reporting an error is always useful, but I can remove that if you prefer.
I note that we deny with virtnet_set_mac_address.
+ }
+ }
+
return 0;
Also, some code duplication with virtnet_set_mac_address here.
Also:
When using the legacy interface, \field{mac} is driver-writable
which provided a way for drivers to update the MAC without
negotiating VIRTIO_NET_F_CTRL_MAC_ADDR.
How about factoring out code in virtnet_set_mac_address
and reusing that?
In fact, we can write in the field only if we have VIRTIO_NET_F_MAC (according to
virtnet_set_mac_address(), and this code is executed only if we do not have
VIRTIO_NET_F_MAC. So I think it's better not factoring the code as we have only the
control queue case to manage.
This will also handle corner cases such as VIRTIO_NET_F_STANDBY
which are not currently addressed.
F_STANDBY is only enabled when virtio-net device MAC address is equal to the VFIO device
MAC address, I don't think it can be enabled when the MAC address is randomly assigned (in
this case it has already failed in net_failover_create(), as it has been called using the
random mac address), it's why I didn't check for it.
free_unregister_netdev:
--
2.39.0
Thanks,
Laurent
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