linux-kernel - Re: [PATCH 3/3] e820: Add the unknown-12 Memory type (DDR3-NvDIMM)

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Date:	Mon, 09 Mar 2015 13:19:35 +0200
From:	Boaz Harrosh <boaz@...xistor.com>
To:	Dan Williams <dan.j.williams@...el.com>
CC:	Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Roger C. Pao" <rcpao.enmotus@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-nvdimm <linux-nvdimm@...ts.01.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Andy Lutomirski <luto@...capital.net>,
	Christoph Hellwig <hch@...radead.org>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH 3/3] e820: Add the unknown-12 Memory type (DDR3-NvDIMM)

On 03/05/2015 10:56 PM, Dan Williams wrote:
> On Thu, Mar 5, 2015 at 2:24 AM, Boaz Harrosh <boaz@...xistor.com> wrote:
>>
<>
>> Now the ACPI comity, as far as I know, did not yet define a
>> standard type for NvDIMM. Also, as far as I know any NvDIMM
>> standard will only be defined for DDR4. So DDR3 NvDIMM is
>> probably stuck with this none STD type.
> 
> There's no relation between E820 types and DDR technology revisions.
> 

Yes and no, I mean the DDR4 has extra legs and signals defined
for NvDIMM. So DDR3 will always mean different style of NvDIMM.

You tell me. Say the standard finally comes out. Will I have a
new bios from Intel for my DDR3 system here in the lab that will
report the new STD type ?

What I meant is that DDR3 is too old for the proposed STD and probably
only DDR4 NvDIMMs will be supported in systems. The way the STD defined
it.

<>
>> In this patch I name type-12 "unknown-12". This is because of
>> ACPI politics that refuse to reserve type-12 as DDR3-NvDIMM
> 
> It's not "politics".  Setting standards takes time and the platforms
> in question simply jumped the gun to enable a proof-of-concept.
> 

So ye, but once you have 100,000 devices out there, then the dichotomy
between standards-takes-time vs proof-of-concept, becomes politics.

This is the definition of politics, when life moves faster than some
"body", the "body" stands on its back feet and shoots fire from
his head.

>> and members keep saying:
>>         "What if ACPI assigns type-12 for something else in future"
>>
>> [And I say: Then just don't. Please?]
> 
> Once a standard number is assigned, platform firmwares can update
> type-12 to that number.  We might consider a compile time override for
> these niche/pre-standard systems that can't/won't update, but it's not
> clear to me that we even need to go that far.
> 

OK, so I do not understand what you want. Yes or No to this patch?

This patch with unknown-12 is for NOW. For systems already running.

So we can differentiate between  reserved-unknown which might mean
type-13 and this here bastard type-12 which we know is NvDIMM but
for future sake we do not call by name?

Or maybe we should call it NVDIMM-12 ?

Thanks
Boaz

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