linux-kernel - Re: [RFC v2 4/4] powerpc/papr_scm: Add cpu hotplug support for nvdimm pmu device

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Message-ID: <569ee30d-29c0-37c4-6f3e-9dd1345f837e@linux.ibm.com>
Date:   Wed, 26 May 2021 14:15:06 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
To:     kajoljain <kjain@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
        linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
        maddy@...ux.vnet.ibm.com, santosh@...six.org,
        vaibhav@...ux.ibm.com, dan.j.williams@...el.com,
        ira.weiny@...el.com, atrajeev@...ux.vnet.ibm.com,
        tglx@...utronix.de, rnsastry@...ux.ibm.com
Subject: Re: [RFC v2 4/4] powerpc/papr_scm: Add cpu hotplug support for nvdimm
 pmu device

On 5/26/21 12:56 PM, kajoljain wrote:
> 
> 
> On 5/25/21 7:46 PM, Peter Zijlstra wrote:
>> On Tue, May 25, 2021 at 06:52:16PM +0530, Kajol Jain wrote:
>>> Patch here adds cpu hotplug functions to nvdimm pmu.
>>
>> I'm thinking "Patch here" qualifies for "This patch", see
>> Documentation/process/submitting-patches.rst .
>>
> Hi Peter,
>     I will reword this commit message.
> 
>>> It adds cpumask to designate a cpu to make HCALL to
>>> collect the counter data for the nvdimm device and
>>> update ABI documentation accordingly.
>>>
>>> Result in power9 lpar system:
>>> command:# cat /sys/devices/nmem0/cpumask
>>> 0
>>
>> Is this specific to the papr thing, or should this be in generic nvdimm
>> code?
> 
> This code is not specific to papr device and we can move it to
> generic nvdimm interface. But do we need to add some checks on whether
> any arch/platform specific driver want that support or we can assume
> that this will be something needed by all platforms?
> 

It says the cpu that should be used to make the hcall. That makes it 
PAPR specific.

-aneesh