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From: Dan Williams <dan.j.williams@intel.com>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Linux ACPI <linux-acpi@vger.kernel.org>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Peter Zijlstra <peterz@infradead.org>,
	Ard Biesheuvel <ardb@kernel.org>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Brice Goglin <Brice.Goglin@inria.fr>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Andy Lutomirski <luto@kernel.org>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Joao Martins <joao.m.martins@oracle.com>
Subject: Re: [PATCH 0/5] Manual definition of Soft Reserved memory devices
Date: Fri, 6 Mar 2020 13:05:30 -0800	[thread overview]
Message-ID: <CAPcyv4jCWtPf0XEHfw6GGGE80k0_wKpoaruopRFJwKcsHk18gw@mail.gmail.com> (raw)
In-Reply-To: <x49a74tnt6n.fsf@segfault.boston.devel.redhat.com>

On Fri, Mar 6, 2020 at 12:07 PM Jeff Moyer <jmoyer@redhat.com> wrote:
>
> Dan Williams <dan.j.williams@intel.com> writes:
>
> > Given the current dearth of systems that supply an ACPI HMAT table, and
> > the utility of being able to manually define device-dax "hmem" instances
> > via the efi_fake_mem= option, relax the requirements for creating these
> > devices. Specifically, add an option (numa=nohmat) to optionally disable
> > consideration of the HMAT and update efi_fake_mem= to behave like
> > memmap=nn!ss in terms of delimiting device boundaries.
>
> So, am I correct in deducing that your primary motivation is testing
> without hardware/firmware support?

My primary motivation is making the dax_kmem facility useful to
shipping platforms that have performance differentiated memory, but
may not have EFI-defined soft-reservations / HMAT (or
non-EFI-ACPI-platform equivalent). I'm anticipating HMAT enabled
platforms where the platform firmware policy for what is
soft-reserved, or not, is not the policy the system owner would pick.
I'd also highlight Joao's work [1] (see the TODO section) as an
indication of the demand for custom carving memory resources and
applying the device-dax memory management interface.

> This looks like a bit of a hack to
> me, and I think maybe it would be better to just emulate the HMAT using
> qemu.  I don't have a strong objection, though.

Yeah, qemu emulation does not help when you, the system owner, have a
different use case than what the bare-metal platform-firmware
envisioned for "specific-purpose memory".

[1]: https://lore.kernel.org/lkml/20200110190313.17144-1-joao.m.martins@oracle.com/
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      reply	other threads:[~2020-03-06 21:05 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-02 22:19 Dan Williams
2020-03-02 22:20 ` [PATCH 1/5] ACPI: NUMA: Add 'nohmat' option Dan Williams
2020-03-18  0:08   ` Dan Williams
2020-03-18  8:24     ` Rafael J. Wysocki
2020-03-18 17:39       ` Dan Williams
2020-03-19  9:30         ` Rafael J. Wysocki
2020-03-02 22:20 ` [PATCH 2/5] efi/fake_mem: Arrange for a resource entry per efi_fake_mem instance Dan Williams
2020-03-03  8:01   ` Ard Biesheuvel
2020-03-02 22:20 ` [PATCH 3/5] ACPI: HMAT: Refactor hmat_register_target_device to hmem_register_device Dan Williams
2020-03-02 22:20 ` [PATCH 4/5] resource: Report parent to walk_iomem_res_desc() callback Dan Williams
2020-03-05 14:42   ` Tom Lendacky
2020-03-17 22:04     ` Dan Williams
2020-03-02 22:20 ` [PATCH 5/5] ACPI: HMAT: Attach a device for each soft-reserved range Dan Williams
2020-03-06 20:07 ` [PATCH 0/5] Manual definition of Soft Reserved memory devices Jeff Moyer
2020-03-06 21:05   ` Dan Williams [this message]

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