netdev - Re: [PATCH net-next 11/12] net: pse-pd: Add support for event reporting using devm_regulator_irq

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Message-ID: <Zv_1ZzwQJ-P36mt6@pengutronix.de>
Date: Fri, 4 Oct 2024 16:02:15 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Andrew Lunn <andrew@...n.ch>
Cc: Kory Maincent <kory.maincent@...tlin.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	Donald Hunter <donald.hunter@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-doc@...r.kernel.org, Kyle Swenson <kyle.swenson@....tech>,
	Dent Project <dentproject@...uxfoundation.org>,
	kernel@...gutronix.de
Subject: Re: [PATCH net-next 11/12] net: pse-pd: Add support for event
 reporting using devm_regulator_irq_helper

On Fri, Oct 04, 2024 at 03:56:33PM +0200, Oleksij Rempel wrote:
> On Thu, Oct 03, 2024 at 05:22:58PM +0200, Andrew Lunn wrote:
> > > Indeed, but regulator API already provide such events, which will even be sent
> > > when we enable or disable the PSE. Should we write a second event management.
> > > Using regulator event API allows to report over current internal events to the
> > > parents regulator the power supply of the PSE which could also do something to
> > > avoid smoke.
> > > 
> > > Or maybe we should add another wrapper which will send PSE ethtool netlink
> > > notification alongside the regulator notifications supported by this patch.
> > > 
> > > > Also, how do regulator events work in combination with network
> > > > namespaces? If you move the interface into a different network
> > > > namespace, do the regulator events get delivered to the root namespace
> > > > or the namespace the interface is in?
> > > 
> > > regulator events are sent in root namespace.
> > 
> > I think we will need two event, the base regulator event, and a
> > networking event. Since it is a regulator, sending a normal regulator
> > event makes a lot of sense. But mapping that regulator event to a
> > netns:ifnam is going to be hard. Anything wanting to take an action is
> > probably going to want to use ethtool, and so needs to be in the
> > correct netns, etc. But it does get messy if there is some sort of
> > software driven prioritisation going on, some daemon needs to pick a
> > victim to reduce power to, and the interfaces are spread over multiple
> > network namespaces.
> > 
> > What i don't know is if we can use an existing event, or we should add
> > a new one. Often rtnetlink_event() is used:
> > 
> > https://elixir.bootlin.com/linux/v6.12-rc1/source/net/core/rtnetlink.c#L6679
> > 
> > but without some PSE information in it, it would be hard to know why
> > it was sent. So we probably either want a generic ethtool event, or a
> > PSE event.
> 
> Hm... assuming we have following scenario:
> 
>                                   .---------   PI 1
>                                  / .---------  PI 2
>                    .========= PSE /----------( PI 3 ) NNS red
>                   //              \----------( PI 4 ) NNS blue
> Main supply      //                `---------( PI 5 ) NNS blue
> o================´--- System, CPU
> 
> In this case we seems to have a new challenge:
> 
> On one side, a system wide power manager should see and mange all ports.
> On other side, withing a name space, we should be able to play in a
> isolated sand box. There is a reason why it is isolated. So, we should
> be able to sandbox power delivery and port prios too. Means, by creating
> network names space, we will need a power names space. 
> 
> I can even imagine a use case: an admin limited access to a switch for
> developer. A developer name space is created with PSE budget and max
> prios available for this name space. This will prevent users from DoSing
> system critical ports.
> 
> At this point, creating a power name space will an overkill for this
> patch set, so it should be enough to allow controlling prios over
> ethtool per port and isolation support if needed.

Oh, sorry, i'm too tired. Too many words are missing in my answer ...

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