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Subject: Re: [PATCH V2 5/8] x86/platform/uv: Add UV Hubbed/Hubless Proc FS
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To:     Ingo Molnar <mingo@kernel.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Borislav Petkov <bp@alien8.de>,
        Christoph Hellwig <hch@infradead.org>,
        Dimitri Sivanich <dimitri.sivanich@hpe.com>,
        Russ Anderson <russ.anderson@hpe.com>,
        Hedi Berriche <hedi.berriche@hpe.com>,
        Steve Wahl <steve.wahl@hpe.com>,
        Justin Ernst <justin.ernst@hpe.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org
References: <20190910145839.604369497@stormcage.eag.rdlabs.hpecorp.net>
 <20190910145840.055590900@stormcage.eag.rdlabs.hpecorp.net>
 <20190911060456.GC104115@gmail.com>
From:   Mike Travis <mike.travis@hpe.com>
Message-ID: <1d7a8b2f-80e0-33bf-85f4-2de719747eeb@hpe.com>
Date:   Wed, 11 Sep 2019 09:05:28 -0700
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On 9/10/2019 11:04 PM, Ingo Molnar wrote:
> 
> * Mike Travis <mike.travis@hpe.com> wrote:
> 
>> @@ -1596,7 +1687,7 @@ static void __init uv_system_init_hub(vo
>>   	uv_nmi_setup();
>>   	uv_cpu_init();
>>   	uv_scir_register_cpu_notifier();
>> -	proc_mkdir("sgi_uv", NULL);
>> +	uv_setup_proc_files(0);
> 
> This slipped through previously: platform drivers have absolutely no
> business mucking in /proc.
> 
> Please describe the hardware via sysfs as pretty much everyone else does.
> 
> Thanks,
> 
> 	Ingo
> 

If I was doing it now I definitely would put it in the sysfs realm.  The 
problem is Jack did it back in (I think) 2007.  The earliest commit I 
could find:

commit a3d732f93785da17e0137210deadb4616f5536fc
Author: Cliff Wickman <cpw@sgi.com>
Date:   Mon Nov 10 16:16:31 2008 -0600

     x86, UV: fix redundant creation of sgi_uv

     Impact: fix double entry creation in /proc

And in the past 12 years probably a hundred user programs are now keying 
of the presence of /proc/sgi_uv to signal this is indeed a UV system. 
Changing the location of this node also affects all the UV utilities 
including those not written by us.