linux-kernel - Re: [PATCH v2 0/6] Manual definition of Soft Reserved memory devices

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Date:   Wed, 25 Mar 2020 11:02:58 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Borislav Petkov <bp@...en8.de>,
        Wei Yang <richardw.yang@...ux.intel.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Brice Goglin <Brice.Goglin@...ia.fr>,
        Thomas Gleixner <tglx@...utronix.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Jeff Moyer <jmoyer@...hat.com>, Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Will Deacon <will@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andy Lutomirski <luto@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Joao Martins <joao.m.martins@...cle.com>
Subject: Re: [PATCH v2 0/6] Manual definition of Soft Reserved memory devices

On Sun, Mar 22, 2020 at 5:28 PM Dan Williams <dan.j.williams@...el.com> wrote:
>
> Changes since v1 [1]:
> - Kill the ifdef'ery in arch/x86/mm/numa.c (Rafael)
>
> - Add a dummy phys_to_target_node() for ARM64 (0day-robot)
>
> - Initialize ->child and ->sibling to NULL in the resource returned by
>   find_next_iomem_res() (Inspired by Tom's feedback even though it does
>   not set them like he suggested)
>
> - Collect Ard's Ack
>
> [1]: http://lore.kernel.org/r/158318759687.2216124.4684754859068906007.stgit@dwillia2-desk3.amr.corp.intel.com
>
> ---
>
> 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 [2] (see the TODO section) as an
> indication of the demand for custom carving memory resources and
> applying the device-dax memory management interface.
>
> 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.
>
> [2]: https://lore.kernel.org/lkml/20200110190313.17144-1-joao.m.martins@oracle.com/
>
> With Ard's and Rafael's ack I'd feel ok taking this through the nvdimm
> tree, please holler if anything still needs some fixups.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

for the whole series.

Thanks!