netdev - Re: [PATCH v2 1/3] net: mana: Add speed support in mana_get_link

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Message-ID: <c481c8a8-4e0f-4498-89f9-988673a584f6@lunn.ch>
Date: Mon, 21 Apr 2025 14:36:43 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Erni Sri Satya Vennela <ernis@...ux.microsoft.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
	decui@...rosoft.com, andrew+netdev@...n.ch, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	longli@...rosoft.com, kotaranov@...rosoft.com, horms@...nel.org,
	mhklinux@...look.com, pasha.tatashin@...een.com,
	kent.overstreet@...ux.dev, brett.creeley@....com,
	schakrabarti@...ux.microsoft.com, shradhagupta@...ux.microsoft.com,
	ssengar@...ux.microsoft.com, leon@...nel.org, rosenp@...il.com,
	paulros@...rosoft.com, linux-hyperv@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-rdma@...r.kernel.org
Subject: Re: [PATCH v2 1/3] net: mana: Add speed support in
 mana_get_link_ksettings

On Sun, Apr 20, 2025 at 11:33:38PM -0700, Erni Sri Satya Vennela wrote:
> Add support for speed in mana ethtool get_link_ksettings
> operation. This feature is not supported by all hardware.

This needs a lot more justification. tc(1) will show you the current
HTB Qdisc setting. No other MAC driver i know of will show you Qdisc
info in ksettings. So why is mana special?

Something your said in an earlier thread might be relevant here. There
are two shaper settings involved. The Hypervisor can configure a
limit, which the VM has no control over. And then you have this second
limit the VM can set, which only has any effect if it is lower than
the hypervisor limit.

The hypervisor limit is much more like the value ksettings represents,
the media speed, which is impossible to go above, and the machine has
no control over. Reporting that limit in ksettings would seem
reasonable. But it does not appear your firmware offers that?

    Andrew

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