On Tue, Aug 27, 2024 at 12:11 AM Dragos Tatulea [off-list ref] wrote:

On 26.08.24 16:24, Andrew Lunn wrote:

quoted

On Mon, Aug 26, 2024 at 11:06:09AM +0200, Dragos Tatulea wrote:

quoted

On 23.08.24 18:54, Carlos Bilbao wrote:

quoted

Hello,

I'm debugging my vDPA setup, and when using ioctl to retrieve the
configuration, I noticed that it's running in half duplex mode:

Configuration data (24 bytes):
  MAC address: (Mac address)
  Status: 0x0001
  Max virtqueue pairs: 8
  MTU: 1500
  Speed: 0 Mb
  Duplex: Half Duplex
  RSS max key size: 0
  RSS max indirection table length: 0
  Supported hash types: 0x00000000

I believe this might be contributing to the underperformance of vDPA.

mlx5_vdpa vDPA devicess currently do not support the VIRTIO_NET_F_SPEED_DUPLEX
feature which reports speed and duplex. You can check the state on the
PF.

Then it should probably report DUPLEX_UNKNOWN.

The speed of 0 also suggests SPEED_UNKNOWN is not being returned. So
this just looks buggy in general.

The virtio spec doesn't mention what those values should be when
VIRTIO_NET_F_SPEED_DUPLEX is not supported.

Jason, should vdpa_dev_net_config_fill() initialize the speed/duplex
fields to SPEED/DUPLEX_UNKNOWN instead of 0?

Spec said

"""
The following two fields, speed and duplex, only exist if
VIRTIO_NET_F_SPEED_DUPLEX is set.
"""

So my understanding is that it is undefined behaviour, and those
fields seems useless before feature negotiation. For safety, it might
be better to initialize them as UNKOWN.

Thanks

Thanks,
Dragos