linux-kernel - Re: [PATCH 0/5] Manual definition of Soft Reserved memory devices

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Date:   Fri, 06 Mar 2020 15:07:28 -0500
From:   Jeff Moyer <jmoyer@...hat.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-acpi@...r.kernel.org, Jason Gunthorpe <jgg@...pe.ca>,
        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>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Brice Goglin <Brice.Goglin@...ia.fr>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "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-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] Manual definition of Soft Reserved memory devices

Dan Williams <dan.j.williams@...el.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?  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.

-Jeff

>
> All review welcome of course, but the E820 changes want an x86
> maintainer ack, the efi_fake_mem update needs Ard, and Rafael has
> previously shepherded the HMAT changes. For the changes to
> kernel/resource.c, where there is no clear maintainer, I just copied the
> last few people to make thoughtful changes in that area. I am happy to
> take these through the nvdimm tree along with these prerequisites
> already in -next:
>
> b2ca916ce392 ACPI: NUMA: Up-level "map to online node" functionality
> 4fcbe96e4d0b mm/numa: Skip NUMA_NO_NODE and online nodes in numa_map_to_online_node()
> 575e23b6e13c powerpc/papr_scm: Switch to numa_map_to_online_node()
> 1e5d8e1e47af x86/mm: Introduce CONFIG_NUMA_KEEP_MEMINFO
> 5d30f92e7631 x86/NUMA: Provide a range-to-target_node lookup facility
> 7b27a8622f80 libnvdimm/e820: Retrieve and populate correct 'target_node' info
>
> Tested with:
>
>         numa=nohmat efi_fake_mem=4G@9G:0x40000,4G@13G:0x40000
>
> ...to create to device-dax instances:
>
> 	# daxctl list -RDu
> 	[
> 	  {
> 	    "path":"\/platform\/hmem.1",
> 	    "id":1,
> 	    "size":"4.00 GiB (4.29 GB)",
> 	    "align":2097152,
> 	    "devices":[
> 	      {
> 	        "chardev":"dax1.0",
> 	        "size":"4.00 GiB (4.29 GB)",
> 	        "target_node":3,
> 	        "mode":"devdax"
> 	      }
> 	    ]
> 	  },
> 	  {
> 	    "path":"\/platform\/hmem.0",
> 	    "id":0,
> 	    "size":"4.00 GiB (4.29 GB)",
> 	    "align":2097152,
> 	    "devices":[
> 	      {
> 	        "chardev":"dax0.0",
> 	        "size":"4.00 GiB (4.29 GB)",
> 	        "target_node":2,
> 	        "mode":"devdax"
> 	      }
> 	    ]
> 	  }
> 	]
>
> ---
>
> Dan Williams (5):
>       ACPI: NUMA: Add 'nohmat' option
>       efi/fake_mem: Arrange for a resource entry per efi_fake_mem instance
>       ACPI: HMAT: Refactor hmat_register_target_device to hmem_register_device
>       resource: Report parent to walk_iomem_res_desc() callback
>       ACPI: HMAT: Attach a device for each soft-reserved range
>
>
>  arch/x86/kernel/e820.c              |   16 +++++-
>  arch/x86/mm/numa.c                  |    4 +
>  drivers/acpi/numa/hmat.c            |   71 +++-----------------------
>  drivers/dax/Kconfig                 |    5 ++
>  drivers/dax/Makefile                |    3 -
>  drivers/dax/hmem/Makefile           |    6 ++
>  drivers/dax/hmem/device.c           |   97 +++++++++++++++++++++++++++++++++++
>  drivers/dax/hmem/hmem.c             |    2 -
>  drivers/firmware/efi/x86_fake_mem.c |   12 +++-
>  include/acpi/acpi_numa.h            |    1 
>  include/linux/dax.h                 |    8 +++
>  kernel/resource.c                   |    1 
>  12 files changed, 156 insertions(+), 70 deletions(-)
>  create mode 100644 drivers/dax/hmem/Makefile
>  create mode 100644 drivers/dax/hmem/device.c
>  rename drivers/dax/{hmem.c => hmem/hmem.c} (98%)
>
> base-commit: 7b27a8622f802761d5c6abd6c37b22312a35343c