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

[Fengguang Wu]

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
> > > 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.
>
> 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 It looks my perception was out of date.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.

Thanks,
Fengguang

> > 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