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

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Date:   Fri, 30 Mar 2018 13:42:00 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Rahul Lakkireddy <rahul.lakkireddy@...lsio.com>
Cc:     Jiri Pirko <jiri@...nulli.us>,
        "netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
        "linux-fsdevel\@vger.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "kexec\@lists.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem\@davemloft.net" <davem@...emloft.net>,
        "viro\@zeniv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "stephen\@networkplumber.org" <stephen@...workplumber.org>,
        "akpm\@linux-foundation.org" <akpm@...ux-foundation.org>,
        "torvalds\@linux-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

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.

Eric