[RFC] Why is set_config not supported in mlx5_vnet?

[Carlos Bilbao <cbilbao@digitalocean.com>]

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. While
looking into how to change this option for Mellanox, I read the following
kernel code in mlx5_vnet.c:

static void mlx5_vdpa_set_config(struct vdpa_device *vdev, unsigned int offset, const void *buf,
                 unsigned int len)
{
    /* not supported */
}

I was wondering why this is the case. Is there another way for me to change
these configuration settings?

Thank you in advance,
Carlos