netdev - Re: [PATCH net-next RFC 01/13] devlink: Add reload level option to devlink reload command

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Message-ID: <20200806112530.0588b3ac@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 6 Aug 2020 11:25:30 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     Moshe Shemesh <moshe@...lanox.com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>,
        Vasundhara Volam <vasundhara-v.volam@...adcom.com>
Subject: Re: [PATCH net-next RFC 01/13] devlink: Add reload level option to
 devlink reload command

On Wed, 5 Aug 2020 13:02:58 +0200 Jiri Pirko wrote:
> Tue, Aug 04, 2020 at 10:39:46PM CEST, kuba@...nel.org wrote:
> >AFAIU the per-driver default is needed because we went too low 
> >level with what the action constitutes. We need maintain the higher
> >level actions.
> >
> >The user clearly did not care if FW was reset during devlink reload
> >before this set, so what has changed? The objective user has is to  
> 
> Well for mlxsw, the user is used to this flow:
> devlink dev flash - flash new fw
> devlink dev reload - new fw is activated and reset and driver instances
> are re-created.

Ugh, if the current behavior already implies fw-activation for some
drivers then the default has to probably be "do all the things" :S

> >activate their config / FW / move to different net ns. 
> >
> >Reloading the driver or resetting FW is a low level detail which
> >achieves different things for different implementations. So it's 
> >not a suitable abstraction -> IOW we need the driver default.  
> 
> I'm confused. So you think we need the driver default?

No, I'm talking about the state of this patch set. _In this patchset_ 
we need a driver default because of the unsuitable abstraction.

Better design would not require it.

> >The work flow for the user is:
> >
> >0. download fw to /lib/firmware
> >1. devlink flash $dev $fw
> >2. if live activation is enabled
> >   yes - devlink reload $dev $live-activate
> >   no - report machine has to be drained for reboot
> >
> >fw-reset can't be $live-activate, because as Jake said fw-reset does
> >not activate the new image for Intel. So will we end up per-driver
> >defaults in the kernel space, and user space maintaining a mapping from  
> 
> Well, that is what what is Moshe's proposal. Per-driver kernel default..
> I'm not sure what we are arguing about then :/

The fact that if I do a pure "driver reload" it will active new
firmware for mlxsw but not for mlx5. In this patchset for mlx5 I need
driver reload fw-reset. And for Intel there is no suitable option.

> >a driver to what a "level" of reset implies.
> >
> >I hope this makes things crystal clear. Please explain what problems
> >you're seeing and extensions you're expecting. A list of user scenarios
> >you foresee would be v. useful.