netdev - Re: [PATCH] net/ncsi: Add Intel OS2BMC OEM command

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Date:   Wed, 14 Sep 2022 09:10:57 +0800
From:   Jiaqing Zhao <jiaqing.zhao@...ux.intel.com>
To:     Sam Mendoza-Jonas <sam@...dozajonas.com>,
        Paul Fertser <fercerpav@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        openbmc@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/ncsi: Add Intel OS2BMC OEM command



On 2022-09-13 21:35, Sam Mendoza-Jonas wrote:
> On September 13, 2022 3:12:06 AM GMT+01:00, Jiaqing Zhao <jiaqing.zhao@...ux.intel.com> wrote:
>>
>>
>> On 2022-09-09 15:43, Paul Fertser wrote:
>>> Hello,
>>>
>>> On Fri, Sep 09, 2022 at 03:34:53PM +0800, Jiaqing Zhao wrote:
>>>>> Can you please outline some particular use cases for this feature?
>>>>>
>>>> It enables access between host and BMC when BMC shares the network connection
>>>> with host using NCSI, like accessing BMC via HTTP or SSH from host. 
>>>
>>> Why having a compile time kernel option here more appropriate than
>>> just running something like "/usr/bin/ncsi-netlink --package 0
>>> --channel 0 --index 3 --oem-payload 00000157200001" (this example uses
>>> another OEM command) on BMC userspace startup?
>>>
>>
>> Using ncsi-netlink is one way, but the package and channel id is undetermined
>> as it is selected at runtime. Calling the netlink command on a nonexistent
>> package/channel may lead to kernel panic.
> 
> If so, that would be a bug :)

Yes but I haven't found the root cause so far, it only panics with some specific
NICs I remember.

>>
>> Why I prefer the kernel option is that it applies the config to all ncsi
>> devices by default when setting up them. This reduces the effort and keeps
>> compatibility. Lots of things in current ncsi kernel driver can be done via
>> commands from userspace, but I think it is not a good idea to have a driver
>> resides on both kernel and userspace.
> 
> BMCs are of course in their own world and there's already some examples of the config option, but how would a system owner be able to disable this without reflashing the BMC?

Given that ncsi driver is a driver binding to the PHY driver, it seems to be unable
to make it a module and have some module options. So far build option seems to be
the only way. Maybe in future sysfs entries can be added to make it configurable at
runtime.