netdev - 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 16:21:57 +0530
From:   Rahul Lakkireddy <rahul.lakkireddy@...lsio.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     "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>,
        "ebiederm@...ssion.com" <ebiederm@...ssion.com>,
        "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

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.

> >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>.
> >