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From: Dan Williams <dan.j.williams@intel.com>
To: Will Deacon <will@kernel.org>
Cc: Linux ACPI <linux-acpi@vger.kernel.org>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Brice Goglin <Brice.Goglin@inria.fr>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	X86 ML <x86@kernel.org>, Joao Martins <joao.m.martins@oracle.com>
Subject: Re: [PATCH v2 6/6] ACPI: HMAT: Attach a device for each soft-reserved range
Date: Wed, 25 Mar 2020 10:10:36 -0700
Message-ID: <CAPcyv4jQDbdUN3pwjkDx-R6Dd3adDSWq+50+O7mqZw5ezNXHeg@mail.gmail.com> (raw)
In-Reply-To: <20200325111039.GA32109@willie-the-truck>

On Wed, Mar 25, 2020 at 4:10 AM Will Deacon <will@kernel.org> wrote:
>
> On Sun, Mar 22, 2020 at 09:12:58AM -0700, Dan Williams wrote:
> > The hmem enabling in commit 'cf8741ac57ed ("ACPI: NUMA: HMAT: Register
> > "soft reserved" memory as an "hmem" device")' only registered ranges to
> > the hmem driver for each soft-reservation that also appeared in the
> > HMAT. While this is meant to encourage platform firmware to "do the
> > right thing" and publish an HMAT, the corollary is that platforms that
> > fail to publish an accurate HMAT will strand memory from Linux usage.
> > Additionally, the "efi_fake_mem" kernel command line option enabling
> > will strand memory by default without an HMAT.
> >
> > Arrange for "soft reserved" memory that goes unclaimed by HMAT entries
> > to be published as raw resource ranges for the hmem driver to consume.
> >
> > Include a module parameter to disable either this fallback behavior, or
> > the hmat enabling from creating hmem devices. The module parameter
> > requires the hmem device enabling to have unique name in the module
> > namespace: "device_hmem".
> >
> > Rather than mark this x86-only, include an interim phys_to_target_node()
> > implementation for arm64.
> >
> > Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Cc: Brice Goglin <Brice.Goglin@inria.fr>
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> > Cc: Jeff Moyer <jmoyer@redhat.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > ---
> >  arch/arm64/mm/numa.c      |   13 +++++++++++++
> >  drivers/dax/Kconfig       |    1 +
> >  drivers/dax/hmem/Makefile |    3 ++-
> >  drivers/dax/hmem/device.c |   33 +++++++++++++++++++++++++++++++++
> >  4 files changed, 49 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> > index 4decf1659700..00fba21eaec0 100644
> > --- a/arch/arm64/mm/numa.c
> > +++ b/arch/arm64/mm/numa.c
> > @@ -468,3 +468,16 @@ int memory_add_physaddr_to_nid(u64 addr)
> >       pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr);
> >       return 0;
> >  }
> > +
> > +/*
> > + * device-dax instance registrations want a valid target-node in case
> > + * they are ever onlined as memory (see hmem_register_device()).
> > + *
> > + * TODO: consult cached numa info
> > + */
> > +int phys_to_target_node(phys_addr_t addr)
> > +{
> > +     pr_warn_once("Unknown target node for memory at 0x%llx, assuming node 0\n",
> > +                     addr);
> > +     return 0;
> > +}
>
> Could you implement a generic version of this by iterating over the nodes
> with for_each_{,online_}node() and checking for intersection with
> node_{start,end}_pfn()?

Interesting. The gap is that node_{start,end}_pfn() requires
node_data[] which to date architectures have only setup for online
nodes. Recall a target node is an offline node that could come online
later. However, reworking offline data into node_data could be the
local solution for arm64, I'd just ask that each of the 6
memory-hotplug capable archs go make that opt-in decision themselves.
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Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-22 16:12 [PATCH v2 0/6] Manual definition of Soft Reserved memory devices Dan Williams
2020-03-22 16:12 ` [PATCH v2 1/6] x86/numa: Cleanup configuration dependent command-line options Dan Williams
2020-03-22 16:12 ` [PATCH v2 2/6] x86/numa: Add 'nohmat' option Dan Williams
2020-03-22 16:12 ` [PATCH v2 3/6] efi/fake_mem: Arrange for a resource entry per efi_fake_mem instance Dan Williams
2020-03-22 16:12 ` [PATCH v2 4/6] ACPI: HMAT: Refactor hmat_register_target_device to hmem_register_device Dan Williams
2020-03-24 19:40   ` Joao Martins
2020-03-24 21:04     ` Dan Williams
2020-03-25 22:32       ` Dan Williams
2020-03-22 16:12 ` [PATCH v2 5/6] resource: Report parent to walk_iomem_res_desc() callback Dan Williams
2020-03-22 16:12 ` [PATCH v2 6/6] ACPI: HMAT: Attach a device for each soft-reserved range Dan Williams
2020-03-24 19:41   ` Joao Martins
2020-03-24 21:06     ` Dan Williams
2020-03-24 21:30       ` Joao Martins
2020-03-25 11:10   ` Will Deacon
2020-03-25 17:10     ` Dan Williams [this message]
2020-03-25 10:02 ` [PATCH v2 0/6] Manual definition of Soft Reserved memory devices Rafael J. Wysocki

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