Re: [PATCH net-next v2 1/2] fs/crashdd: add API to collect hardware dump in second kernel

From: Jiri Pirko <jiri@resnulli.us>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Indranil Choudhury <indranil@chelsio.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Nirranjan Kirubaharan <nirranjan@chelsio.com>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>,
	Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>,
	"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
	"davem@davemloft.net" <davem@davemloft.net>,
	Ganesh GR <ganeshgr@chelsio.com>
Subject: Re: [PATCH net-next v2 1/2] fs/crashdd: add API to collect hardware dump in second kernel
Date: Mon, 2 Apr 2018 11:11:43 +0200	[thread overview]
Message-ID: <20180402091143.GD3313@nanopsycho> (raw)
In-Reply-To: <87k1tt2yo7.fsf@xmission.com>

Fri, Mar 30, 2018 at 08:42:00PM CEST, ebiederm@xmission.com wrote:
>Rahul Lakkireddy <rahul.lakkireddy@chelsio.com> writes:
>
>> On Friday, March 03/30/18, 2018 at 16:09:07 +0530, Jiri Pirko wrote:
>>> Sat, Mar 24, 2018 at 11:56:33AM CET, rahul.lakkireddy@chelsio.com wrote:
>>> >Add a new module crashdd that exports the /sys/kernel/crashdd/
>>> >directory in second kernel, containing collected hardware/firmware
>>> >dumps.
>>> >
>>> >The sequence of actions done by device drivers to append their device
>>> >specific hardware/firmware logs to /sys/kernel/crashdd/ directory are
>>> >as follows:
>>> >
>>> >1. During probe (before hardware is initialized), device drivers
>>> >register to the crashdd module (via crashdd_add_dump()), with
>>> >callback function, along with buffer size and log name needed for
>>> >firmware/hardware log collection.
>>> >
>>> >2. Crashdd creates a driver's directory under
>>> >/sys/kernel/crashdd/<driver>. Then, it allocates the buffer with
>>> 
>>> This smells. I need to identify the exact ASIC instance that produced
>>> the dump. To identify by driver name does not help me if I have multiple
>>> instances of the same driver. This looks wrong to me. This looks like
>>> a job for devlink where you have 1 devlink instance per 1 ASIC instance.
>>> 
>>> Please see:
>>> http://patchwork.ozlabs.org/project/netdev/list/?series=36524
>>> 
>>> I bevieve that the solution in the patchset could be used for
>>> your usecase too.
>>> 
>>> 
>>
>> The sysfs approach proposed here had been dropped in favour exporting
>> the dumps as ELF notes in /proc/vmcore.
>>
>> Will be posting the new patches soon.
>
>The concern was actually how you identify which device that came from.
>Where you read the identifier changes but sysfs or /proc/vmcore the
>change remains valid.

Yeah. I still don't see how you link the dump and the device. Rahul, did
you look at the patchset I pointed out?
Thanks!

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