Re: [Linux-nvdimm] [PATCH v2 11/20] libnd, nd_pmem: add libnd support to the pmem driver

From: Phil Pokorny
Date: Tue Apr 28 2015 - 18:21:49 EST

On Tue, Apr 28, 2015 at 2:04 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> On Tue, Apr 28, 2015 at 11:25 AM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>> +config ND_E820
>> + tristate "E820: Support the E820-type-12 PMEM convention"
>> + depends on X86_PMEM_LEGACY
>> + default m if X86_PMEM_LEGACY
>> + select LIBND
>> + help
>> + Prior to ACPI 6 some platforms advertised peristent memory
>> + via type-12 e820 memory ranges. Create a libnd bus and
>> + attach an instance of the pmem driver to these ranges.
>> +
> How about something like:
> "This driver allows libnd to work with legacy, pre-ACPI 6 NVDIMMs.
> This enables such devices to be exposed as block devices using PMEM.
> The legacy NVDIMM interface is problematic. This driver will not work
> if you boot using UEFI, and some NVDIMMs and motherboards that work
> with this driver may require proprietary code in order to work
> reliably."

Perhaps not "problematic" but "requires a BIOS in Legacy mode"

It might also mention that if you use the kernel command line
memmap=nn!ss syntax it adds
a type 12 region to the e820 map and so you would want this support.

If you have a motherboard with UEFI support for NVDIMM's that would be
the recommended

Phil P.

Philip Pokorny, RHCE
Chief Technology Officer
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