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

[Johannes Berg <johannes@sipsolutions.net>]

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