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

On Tue, Apr 28, 2015 at 2:04 PM, Andy Lutomirski <luto(a)amacapital.net&gt; wrote: > On Tue, Apr 28, 2015 at 11:25 AM, Dan Williams <dan.j.williams(a)intel.com&gt; 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 configuration.