linux-kernel - Re: [PATCH v3] powerpc/pseries: read the lpar name from the firmware

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Date:   Tue, 7 Dec 2021 18:18:40 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     Nathan Lynch <nathanl@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3] powerpc/pseries: read the lpar name from the firmware

On 07/12/2021, 18:07:50, Nathan Lynch wrote:
> Laurent Dufour <ldufour@...ux.ibm.com> writes:
>> On 07/12/2021, 15:32:39, Nathan Lynch wrote:
>>> Is there a reasonable fallback for VMs where this parameter doesn't
>>> exist? PowerVM partitions should always have it, but what do we want the
>>> behavior to be on other hypervisors?
>>
>> In that case, there is no value displayed in the /proc/powerpc/lparcfg and
>> the lparstat -i command will fall back to the device tree value. I can't
>> see any valid reason to report the value defined in the device tree
>> here.
> 
> Here's a valid reason :-)
> 
> lparstat isn't the only possible consumer of the interface, and the
> 'ibm,partition-name' property and the dynamic system parameter clearly
> serve a common purpose. 'ibm,partition-name' is provided by qemu.

If the hypervisor is not providing this value, this is not the goal of this
interface to fetch it from the device tree.

Any consumer should be able to fall back on the device tree value, and
there is no added value to do such a trick in the kernel when it can be
done in the user space.

> In any case, the function should not print an error when the return
> value is -3 (parameter not supported).

That's a valid requirement.