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

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Message-ID: <20180330103907.GC3313@nanopsycho>
Date:   Fri, 30 Mar 2018 12:39:07 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Rahul Lakkireddy <rahul.lakkireddy@...lsio.com>
Cc:     netdev@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        davem@...emloft.net, viro@...iv.linux.org.uk,
        ebiederm@...ssion.com, stephen@...workplumber.org,
        akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
        ganeshgr@...lsio.com, nirranjan@...lsio.com, indranil@...lsio.com
Subject: Re: [PATCH net-next v2 1/2] fs/crashdd: add API to collect hardware
 dump in second kernel

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.


>requested size and invokes the device driver's registered callback
>function.
>
>3. Device driver collects all hardware/firmware logs into the buffer
>and returns control back to crashdd.
>
>4. Crashdd exposes the buffer as a binary file via
>/sys/kernel/crashdd/<driver>/<dump_file>.
>