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

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Date:   Fri, 22 May 2020 22:46:07 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Jakub Kicinski <kuba@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>
Cc:     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, 2020-05-22 at 10:17 -0700, Jakub Kicinski wrote:

> > > --- 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?

Wait, yeah, what?

> 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.

Agree. I don't actually operate anything, but still ...

Thinking about this - maybe there's a way to still combine devcoredump
and devlink somehow?

Or (optionally) make devlink trigger devcoredump while userspace
migrates?

> > 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.

FWIW, I still completely disagree on that taint. You (Luis) obviously
have been running into a bug in that driver, I doubt the firmware
actually managed to wedge the hardware.

But even if it did, that's still not really a kernel taint. The kernel
itself isn't in any way affected by this.

Yes, the system is in a weird state now. But that's *not* equivalent to
"kernel tainted".

> 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.

Like I said above, do you think it'd be feasible to make a devcoredump
out of devlink health reports? And can the report be in a way that we
control the file format, or are there limits? I guess I should read the
code to find out, but I figure you probably just know. But feel free to
tell me to read it :)

The reason I'm asking is that it's starting to sound like we really
ought to be implementing devlink, but we've got a bunch of
infrastructure that uses the devcoredump, and it'll take time
(significantly so) to change all that...

johannes