Re: [Linux-nvdimm] [PATCH v2] pmem: Initial version of persistent memory driver

From: Dan Williams
Date: Fri Sep 19 2014 - 12:27:42 EST


On Tue, Sep 16, 2014 at 6:54 AM, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote:
> Boaz Harrosh <boaz@xxxxxxxxxxxxx> writes:
>
>> On 09/11/2014 07:31 PM, Dan Williams wrote:
>> <>
>>>
>>> The point I am getting at is not requiring a priori knowledge of the
>>> physical memory map of a system. Rather, place holder variables to
>>> enable simple dynamic discovery.
>>>
>>
>> "simple dynamic discovery" does not yet exist and when the DDR4 NvDIMM
>> will be released then we still have those DDR3 out there which will
>> not work with the new discovery, which I need to support as well.
>
> Boaz,
>
> Are you telling me that vendors are shipping parts that present
> themselves as E820_RAM, and that you have to manually block off the
> addresses from the kernel using the kernel command line? If that is
> true, then that is just insane and unsupportable. All the hardware I
> have access to:
> 1) does not present itself as normal memory and
> 2) provides some means for discovering its address and size

Jeff,

Yes, agree.

Boaz,

The UEFI organization is in the process of defining a generic
specification for platform non-volatile memory resources. Let's wait
until that is publicly available before adding any new device
discovery capabilities to pmem.
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