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

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Date:   Mon, 2 Apr 2018 11:11:43 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Rahul Lakkireddy <rahul.lakkireddy@...lsio.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "stephen@...workplumber.org" <stephen@...workplumber.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        Ganesh GR <ganeshgr@...lsio.com>,
        Nirranjan Kirubaharan <nirranjan@...lsio.com>,
        Indranil Choudhury <indranil@...lsio.com>
Subject: Re: [PATCH net-next v2 1/2] fs/crashdd: add API to collect hardware
 dump in second kernel

Fri, Mar 30, 2018 at 08:42:00PM CEST, ebiederm@...ssion.com wrote:
>Rahul Lakkireddy <rahul.lakkireddy@...lsio.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@...lsio.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!