netdev - Re: [question] About triggering a region snapshot through the devlink cmd

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Message-ID: <02874ECE860811409154E81DA85FBB58B26FA36F@fmsmsx101.amr.corp.intel.com>
Date:   Tue, 7 Jan 2020 17:33:36 +0000
From:   "Keller, Jacob E" <jacob.e.keller@...el.com>
To:     "jiri@...nulli.us" <jiri@...nulli.us>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "jiri@...lanox.com" <jiri@...lanox.com>,
        "linuxarm@...wei.com" <linuxarm@...wei.com>,
        "linyunsheng@...wei.com" <linyunsheng@...wei.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "valex@...lanox.com" <valex@...lanox.com>
Subject: Re: [question] About triggering a region snapshot through the
 devlink cmd

On 2019/9/27 16:13, Jiri Pirko wrote:
> Fri, Sep 27, 2019 at 09:40:47AM CEST, linyunsheng@...wei.com wrote:
>> Hi, Jiri & Alex
>>
>>    It seems that a region' snapshot is only created through the
>> driver when some error is detected, for example:
>> mlx4_crdump_collect_fw_health() -> devlink_region_snapshot_create()
>>
>>    We want to trigger a region' snapshot creation through devlink
>> cmd, maybe by adding the "devlink region triger", because we want
>> to check some hardware register/state when the driver or the hardware
>> does not detect the error sometimes.
>>
>> Does about "devlink region triger" make sense?
>>
>> If yes, is there plan to implement it? or any suggestion to implement
>> it?
> 
> Actually, the plan is co convert mlx4 to "devlink health" api. Mlx5
> already uses that.
> 
> You should look into "devlink health".

Hi Jiri,

I agree, the mlx4 firmware dump stuff should use the devlink health API, as it's for error conditions.

I've recently been investigating using devlink regions to expose non-error regions where it really does make sense to "trigger" a snapshot.

The original region commit message indicates that there were plans to support requesting snapshots, and even potentially writing to the region directly.

I wanted to use a region to expose some set of flash/NVM contents. Being able to request a snapshot is essential in this case. I saw that netdevsim does this through a debugfs hook, but that really doesn't make sense to me for a production driver.

It makes sense to me to be able to trigger a region snapshot directly through devlink. Should I spin up some patches to implement it?

Thanks,
Jake