netdev - Re: [PATCH/RFC net-next 2/3] devlink: Add new "max_vf

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Message-ID: <2af4e971-b480-6aff-c26b-6fd60b7523fb@gmail.com>
Date:   Tue, 20 Sep 2022 19:27:48 +0100
From:   Edward Cree <ecree.xilinx@...il.com>
To:     Simon Horman <simon.horman@...igine.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, oss-drivers@...igine.com,
        Diana Wang <na.wang@...igine.com>,
        Peng Zhang <peng.zhang@...igine.com>
Subject: Re: [PATCH/RFC net-next 2/3] devlink: Add new "max_vf_queue" generic
 device param

On 20/09/2022 16:14, Simon Horman wrote:
> From: Peng Zhang <peng.zhang@...igine.com>
> 
> VF max-queue-number is the MAX num of queues which the VF has.
> 
> Add new device generic parameter to configure the max-queue-number
> of the each VF to be generated dynamically.
> 
> The string format is decided ad vendor specific. The suggested
> format is ...-V-W-X-Y-Z, the V represents generating V VFs that
> have 16 queues, the W represents generating W VFs that have 8
> queues, and so on, the Z represents generating Z VFs that have
> 1 queue.

I don't like this.
If I'm correctly understanding, it hardcodes an assumption that
 lower-numbered VFs will be the ones with more queues, and also
 makes it difficult to change a VF's max-queues on the fly.
Why not instead have a per-VF operation to set that VF's max
 queue count?  Ideally through the VF representor, perhaps as
 an ethtool param/tunable, rather than devlink.  Then the
 mechanism is flexible and makes no assumptions about policy.

-ed