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

From: Fengguang Wu
Date: Thu Dec 27 2018 - 22:28:05 EST

On Thu, Dec 27, 2018 at 11:32:06AM -0800, Yang Shi wrote:
On Wed, Dec 26, 2018 at 9:13 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote:

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
> 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.

It is correct. We already have Dave's patches + Dan's patch (added
target_node field) work on our machine which has SRAT.

Thanks for the correction. It looks my perception was out of date.
So we can follow Dave+Dan's patches to create the PMEM NUMA nodes.


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