netdev - Re: HW communication debugging interface

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Message-ID: <20151006081457.GD2165@nanopsycho.orion>
Date:	Tue, 6 Oct 2015 10:14:57 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	Andrew Lunn <andrew@...n.ch>, "Rosen, Rami" <rami.rosen@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"eladr@...lanox.com" <eladr@...lanox.com>,
	"idosch@...lanox.com" <idosch@...lanox.com>
Subject: Re: HW communication debugging interface - ideas?

Mon, Oct 05, 2015 at 05:47:09PM CEST, john.fastabend@...il.com wrote:
>On 15-10-05 08:35 AM, Jiri Pirko wrote:
>> Mon, Oct 05, 2015 at 05:29:09PM CEST, john.fastabend@...il.com wrote:
>>> On 15-10-05 08:18 AM, Jiri Pirko wrote:
>>>> Mon, Oct 05, 2015 at 04:58:42PM CEST, andrew@...n.ch wrote:
>>>>> On Mon, Oct 05, 2015 at 04:55:42PM +0200, Jiri Pirko wrote:
>>>>>> Mon, Oct 05, 2015 at 04:49:41PM CEST, andrew@...n.ch wrote:
>>>>>>>>> Are you referring here to messages of the EMAD protocol ?
>>>>>>>
>>>>>>> I know nothing about this protocol.....
>>>>>>>
>>>>>>> Does it at least use standard Ethernet framing? Source and Destination
>>>>>>> header and an EtherType which mean EMAD?
>>>>>>
>>>>>> Yep, but that does not really matter. I believe we should find debugging
>>>>>> interface which is protocol agnostic. Just arbitrary messages
>>>>>> monitoring.
>>>>>
>>>>> Hi Jiri
>>>>>
>>>>> O.K, it is just that you mentioned wireshark. Passing the frames to
>>>>> network interface taps would make this trivial.
>>>>
>>>> That is true. But using netlink+nlmon would do the same.
>>>
>>> Also I guess if you go this direction you want to make it generic
>>> enough for any drivers to use it to snoop software/firmware msgs. This
>>> is common across many devices.
>> 
>> Yes, definitelly, this should be something generic to be usable for
>> every device type.
>> 
>> 
>>>
>>> In the past though I've just used ethtool dump commands and some
>>> "scripts" on top of this to debug devices. And when it got really
>>> bad wrote some throw away code to debug my issue. I guess it might
>>> be nice to have something in the kernel to improve this but have
>>> you considered using the tracing features that already exist?
>> 
>> Which ones do you have in mind?
>> 
>
>I was thinking something like kprobes+bpf to dump a trace and
>then a lua script in wireshark to parse the input and pretty
>print it for users. This might get you good-enough support without
>having to carry it around in the kernel just so we can debug
>the devices. We could build some libs/pkgs around it in userspace
>and get it published somewhere so we can all work on it together.

Well, I was thinking rather about some standard interface, not dependent
on actual kernel internals.


>
>I suspect the primary users for this will be developers anyways
>and maybe some users who have a real nasty bug.
>
>> 
>>>
>>> .John
>>>
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>>>
>
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