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

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Message-ID: <24dbecec-d114-4150-87df-33dfbacaec54@nvidia.com>
Date: Mon, 26 Aug 2024 18:10:30 +0200
From: Dragos Tatulea <dtatulea@...dia.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Carlos Bilbao <cbilbao@...italocean.com>, mst@...hat.com,
 jasowang@...hat.com, virtualization@...ts.linux-foundation.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 eperezma@...hat.com, sashal@...nel.org, yuehaibing@...wei.com,
 steven.sistare@...cle.com
Subject: Re: [RFC] Why is set_config not supported in mlx5_vnet?

On 26.08.24 16:24, Andrew Lunn wrote:
> On Mon, Aug 26, 2024 at 11:06:09AM +0200, Dragos Tatulea wrote:
>>
>>
>> On 23.08.24 18:54, Carlos Bilbao wrote:
>>> 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?

Thanks,
Dragos