Re: [RFC][PATCH v2 01/21] e820: cheat PMEM as DRAM

[Dan Williams]

On Wed, Dec 26, 2018 at 8:11 PM Fengguang Wu <fengguang.wu@xxxxxxxxx> wrote:
>
> On Wed, Dec 26, 2018 at 07:41:41PM -0800, Matthew Wilcox wrote:
> >On Wed, Dec 26, 2018 at 09:14:47PM +0800, Fengguang Wu wrote:
> >> From: Fan Du <fan.du@xxxxxxxxx>
> >>
> >> This is a hack to enumerate PMEM as NUMA nodes.
> >> It's necessary for current BIOS that don't yet fill ACPI HMAT table.
> >>
> >> WARNING: take care to backup. It is mutual exclusive with libnvdimm
> >> subsystem and can destroy ndctl managed namespaces.
> >
> >Why depend on firmware to present this "correctly"?  It seems to me like
> >less effort all around to have ndctl label some namespaces as being for
> >this kind of use.
>
> Dave Hansen may be more suitable to answer your question. He posted
> patches to make PMEM NUMA node coexist with libnvdimm and ndctl:
>
> [PATCH 0/9] Allow persistent memory to be used like normal RAM
> https://lkml.org/lkml/2018/10/23/9
>
> That depends on future BIOS. So we did this quick hack to test out
> PMEM NUMA node for the existing BIOS.

No, it does not depend on a future BIOS.

Willy, have a look here [1], here [2], and here [3] for the
work-in-progress ndctl takeover approach (actually 'daxctl' in this
case).

[1]: https://lkml.org/lkml/2018/10/23/9
[2]: https://lkml.org/lkml/2018/10/31/243
[3]: https://lists.01.org/pipermail/linux-nvdimm/2018-November/018677.html