netdev - [RFC] Why is set_config not supported in mlx5

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Message-ID: <33feec1a-2c5d-46eb-8d66-baa802130d7f@digitalocean.com>
Date: Fri, 23 Aug 2024 11:54:13 -0500
From: Carlos Bilbao <cbilbao@...italocean.com>
To: eli@...lanox.com, mst@...hat.com, jasowang@...hat.com,
 xuanzhuo@...ux.alibaba.com, dtatulea@...dia.com
Cc: virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, mst@...hat.com, kvm@...r.kernel.org,
 eperezma@...hat.com, sashal@...nel.org, yuehaibing@...wei.com,
 steven.sistare@...cle.com
Subject: [RFC] Why is set_config not supported in mlx5_vnet?

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