Message-ID: <38aaa1e8-1941-8b84-6cc6-b773f31112f8@linux.ibm.com>
Date:   Tue, 7 Dec 2021 18:24:36 +0100
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Subject: Re: [PATCH v3] powerpc/pseries: read the lpar name from the firmware
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From:   Laurent Dufour <ldufour@linux.ibm.com>
To:     Nathan Lynch <nathanl@linux.ibm.com>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
References: <20211203154321.13168-1-ldufour@linux.ibm.com>
 <87bl1so588.fsf@linux.ibm.com>
 <bbaa0d78-a09f-3ce3-25a9-67434039b741@linux.ibm.com>
 <878rwwny1l.fsf@linux.ibm.com>
 <21eb4749-42b1-da78-8833-00d360fa36e5@linux.ibm.com>
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On 07/12/2021, 18:18:40, Laurent Dufour wrote:
> On 07/12/2021, 18:07:50, Nathan Lynch wrote:
>> Laurent Dufour <ldufour@linux.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.

I sent a v4 which is printing an error message even if the parameter is not
supported by the hypervisor.

This is unlikely and since this a call to pr_err_once(), it would be
printed only once, so not really annoying. I don't think a v5 is required
for such a minor message.