linux-kernel - Re: [RFC 1/2] devlink: add simple fw crash helpers

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Message-ID: <20200522214929.GB11244@42.do-not-panic.com>
Date:   Fri, 22 May 2020 21:49:29 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     johannes@...solutions.net, derosier@...il.com,
        greearb@...delatech.com, jeyu@...nel.org,
        akpm@...ux-foundation.org, arnd@...db.de, rostedt@...dmis.org,
        mingo@...hat.com, aquini@...hat.com, cai@....pw, dyoung@...hat.com,
        bhe@...hat.com, peterz@...radead.org, tglx@...utronix.de,
        gpiccoli@...onical.com, pmladek@...e.com, tiwai@...e.de,
        schlad@...e.de, andriy.shevchenko@...ux.intel.com,
        keescook@...omium.org, daniel.vetter@...ll.ch, will@...nel.org,
        mchehab+samsung@...nel.org, kvalo@...eaurora.org,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        ath10k@...ts.infradead.org, jiri@...nulli.us,
        briannorris@...omium.org
Subject: Re: [RFC 1/2] devlink: add simple fw crash helpers

On Fri, May 22, 2020 at 10:17:38AM -0700, Jakub Kicinski wrote:
> On Fri, 22 May 2020 05:20:46 +0000 Luis Chamberlain wrote:
> > > diff --git a/net/core/Makefile b/net/core/Makefile
> > > index 3e2c378e5f31..6f1513781c17 100644
> > > --- a/net/core/Makefile
> > > +++ b/net/core/Makefile
> > > @@ -31,7 +31,7 @@ obj-$(CONFIG_LWTUNNEL_BPF) += lwt_bpf.o
> > >  obj-$(CONFIG_BPF_STREAM_PARSER) += sock_map.o
> > >  obj-$(CONFIG_DST_CACHE) += dst_cache.o
> > >  obj-$(CONFIG_HWBM) += hwbm.o
> > > -obj-$(CONFIG_NET_DEVLINK) += devlink.o
> > > +obj-$(CONFIG_NET_DEVLINK) += devlink.o devlink_simple_fw_reporter.o  
> > 
> > This was looking super sexy up to here. This is networking specific.
> > We want something generic for *anything* that requests firmware.
> 
> You can't be serious. It's network specific because of how the Kconfig
> is named?

Kconfig? What has that to do with anything? The issue I have is that the
solution I am looking for is for it to be agnostic to the subsystem. I
have found similar firmware crashes on gpu, media, scsci.

> Working for a company operating large data centers I would strongly
> prefer if we didn't have ten different ways of reporting firmware
> problems in the fleet.

Indeed.

> > I'm afraid this won't work for something generic. I don't think its
> > throw-away work though, the idea to provide a generic interface to
> > dump firmware through netlink might be nice for networking, or other
> > things.
> > 
> > But I have a feeling we'll want something still more generic than this.
> 
> Please be specific. Saying generic a lot is not helpful. The code (as
> you can see in this patch) is in no way network specific. Or are you
> saying there are machines out there running without netlink sockets?

No, I am saying I want something to work with any struct device.

> > So networking may want to be aware that a firmware crash happened as
> > part of this network device health thing, but firmware crashing is a
> > generic thing.
> > 
> > I have now extended my patch set to include uvents and I am more set on
> > that we need the taint now more than ever.
> 
> Please expect my nack if you're trying to add this to networking
> drivers.

The uevent mechanism is not for networking.

The taint however is, and I'd like to undertand how it is you do not see
that an undesirable requirement for a reboot is a clear case for a taint.

> The irony is you have a problem with a networking device and all the
> devices your initial set touched are networking. Two of the drivers 
> you touched either have or will soon have devlink health reporters
> implemented.

That is all great, and I don't think its a bad idea to add
infrastructure / extend it to get more information about a firmware
crash dump. However, suggesting that devlink is the only solution we
need in the kernel without considering other subsystems is what I am
suggesting doesn't suit my needs. Networking was just the first
subsystem I am taclking now but I have patches where similar situations
happen across the kernel.

  Luis