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References: <20190116175804.30196-1-keith.busch@intel.com> <20190116175804.30196-4-keith.busch@intel.com>
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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Thu, 17 Jan 2019 12:00:53 +0100
Message-ID: <CAJZ5v0hEg3V7FoE6arwTTodVQ4uUZNLpwdOpjzh7PjqB3jguGw@mail.gmail.com>
Subject: Re: [PATCHv4 03/13] acpi/hmat: Parse and report heterogeneous memory
To:     Keith Busch <keith.busch@intel.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rafael Wysocki <rafael@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Dan Williams <dan.j.williams@intel.com>
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On Wed, Jan 16, 2019 at 6:59 PM Keith Busch <keith.busch@intel.com> wrote:
>
> Systems may provide different memory types and export this information
> in the ACPI Heterogeneous Memory Attribute Table (HMAT). Parse these
> tables provided by the platform and report the memory access and caching
> attributes.
>
> Signed-off-by: Keith Busch <keith.busch@intel.com>
> ---
>  drivers/acpi/Kconfig       |   1 +
>  drivers/acpi/Makefile      |   1 +
>  drivers/acpi/hmat/Kconfig  |   8 ++
>  drivers/acpi/hmat/Makefile |   1 +
>  drivers/acpi/hmat/hmat.c   | 180 +++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 191 insertions(+)
>  create mode 100644 drivers/acpi/hmat/Kconfig
>  create mode 100644 drivers/acpi/hmat/Makefile
>  create mode 100644 drivers/acpi/hmat/hmat.c
>
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index 90ff0a47c12e..b377f970adfd 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -465,6 +465,7 @@ config ACPI_REDUCED_HARDWARE_ONLY
>           If you are unsure what to do, do not enable this option.
>
>  source "drivers/acpi/nfit/Kconfig"
> +source "drivers/acpi/hmat/Kconfig"
>
>  source "drivers/acpi/apei/Kconfig"
>  source "drivers/acpi/dptf/Kconfig"
> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> index 7c6afc111d76..bff8fbe5a6ab 100644
> --- a/drivers/acpi/Makefile
> +++ b/drivers/acpi/Makefile
> @@ -79,6 +79,7 @@ obj-$(CONFIG_ACPI_PROCESSOR)  += processor.o
>  obj-$(CONFIG_ACPI)             += container.o
>  obj-$(CONFIG_ACPI_THERMAL)     += thermal.o
>  obj-$(CONFIG_ACPI_NFIT)                += nfit/
> +obj-$(CONFIG_ACPI_HMAT)                += hmat/

Yes, I prefer it to go into a separate directory.

Who do you want to maintain it, me or Dan?

>  obj-$(CONFIG_ACPI)             += acpi_memhotplug.o
>  obj-$(CONFIG_ACPI_HOTPLUG_IOAPIC) += ioapic.o
>  obj-$(CONFIG_ACPI_BATTERY)     += battery.o
> diff --git a/drivers/acpi/hmat/Kconfig b/drivers/acpi/hmat/Kconfig
> new file mode 100644
> index 000000000000..a4034d37a311
> --- /dev/null
> +++ b/drivers/acpi/hmat/Kconfig
> @@ -0,0 +1,8 @@
> +# SPDX-License-Identifier: GPL-2.0
> +config ACPI_HMAT
> +       bool "ACPI Heterogeneous Memory Attribute Table Support"
> +       depends on ACPI_NUMA
> +       help
> +        Parses representation of the ACPI Heterogeneous Memory Attributes
> +        Table (HMAT) and set the memory node relationships and access
> +        attributes.

What about:

"If set, this option causes the kernel to set the memory NUMA node
relationships and access attributes in accordance with ACPI HMAT
(Heterogeneous Memory Attributes Table)."

> diff --git a/drivers/acpi/hmat/Makefile b/drivers/acpi/hmat/Makefile
> new file mode 100644
> index 000000000000..e909051d3d00
> --- /dev/null
> +++ b/drivers/acpi/hmat/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_ACPI_HMAT) := hmat.o
> diff --git a/drivers/acpi/hmat/hmat.c b/drivers/acpi/hmat/hmat.c
> new file mode 100644
> index 000000000000..833a783868d5
> --- /dev/null
> +++ b/drivers/acpi/hmat/hmat.c
> @@ -0,0 +1,180 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Heterogeneous Memory Attributes Table (HMAT) representation
> + *
> + * Copyright (c) 2018, Intel Corporation.

Can you put a comment describing the code somewhat in here?

> + */
> +
> +#include <acpi/acpi_numa.h>
> +#include <linux/acpi.h>
> +#include <linux/bitops.h>
> +#include <linux/cpu.h>
> +#include <linux/device.h>
> +#include <linux/init.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/node.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>

Are all of the headers above really necessary to build the code?

> +
> +static __init const char *hmat_data_type(u8 type)
> +{
> +       switch (type) {
> +       case ACPI_HMAT_ACCESS_LATENCY:
> +               return "Access Latency";
> +       case ACPI_HMAT_READ_LATENCY:
> +               return "Read Latency";
> +       case ACPI_HMAT_WRITE_LATENCY:
> +               return "Write Latency";
> +       case ACPI_HMAT_ACCESS_BANDWIDTH:
> +               return "Access Bandwidth";
> +       case ACPI_HMAT_READ_BANDWIDTH:
> +               return "Read Bandwidth";
> +       case ACPI_HMAT_WRITE_BANDWIDTH:
> +               return "Write Bandwidth";
> +       default:
> +               return "Reserved";
> +       };
> +}
> +
> +static __init const char *hmat_data_type_suffix(u8 type)
> +{
> +       switch (type) {
> +       case ACPI_HMAT_ACCESS_LATENCY:
> +       case ACPI_HMAT_READ_LATENCY:
> +       case ACPI_HMAT_WRITE_LATENCY:
> +               return " nsec";
> +       case ACPI_HMAT_ACCESS_BANDWIDTH:
> +       case ACPI_HMAT_READ_BANDWIDTH:
> +       case ACPI_HMAT_WRITE_BANDWIDTH:
> +               return " MB/s";
> +       default:
> +               return "";
> +       };
> +}
> +
> +static __init int hmat_parse_locality(union acpi_subtable_headers *header,
> +                                     const unsigned long end)
> +{
> +       struct acpi_hmat_locality *loc = (void *)header;
> +       unsigned int init, targ, total_size, ipds, tpds;
> +       u32 *inits, *targs, value;
> +       u16 *entries;
> +       u8 type;
> +
> +       if (loc->header.length < sizeof(*loc)) {
> +               pr_err("HMAT: Unexpected locality header length: %d\n",
> +                       loc->header.length);

Why pr_err()?  Is the error really high-prio?

Same below.

> +               return -EINVAL;
> +       }
> +
> +       type = loc->data_type;
> +       ipds = loc->number_of_initiator_Pds;
> +       tpds = loc->number_of_target_Pds;
> +       total_size = sizeof(*loc) + sizeof(*entries) * ipds * tpds +
> +                    sizeof(*inits) * ipds + sizeof(*targs) * tpds;
> +       if (loc->header.length < total_size) {
> +               pr_err("HMAT: Unexpected locality header length:%d, minimum required:%d\n",
> +                       loc->header.length, total_size);
> +               return -EINVAL;
> +       }
> +
> +       pr_info("HMAT: Locality: Flags:%02x Type:%s Initiator Domains:%d Target Domains:%d Base:%lld\n",
> +               loc->flags, hmat_data_type(type), ipds, tpds,
> +               loc->entry_base_unit);
> +
> +       inits = (u32 *)(loc + 1);
> +       targs = &inits[ipds];
> +       entries = (u16 *)(&targs[tpds]);
> +       for (targ = 0; targ < tpds; targ++) {
> +               for (init = 0; init < ipds; init++) {
> +                       value = entries[init * tpds + targ];
> +                       value = (value * loc->entry_base_unit) / 10;
> +                       pr_info("  Initiator-Target[%d-%d]:%d%s\n",
> +                               inits[init], targs[targ], value,
> +                               hmat_data_type_suffix(type));
> +               }
> +       }
> +       return 0;
> +}

The format and meaning of what is printed into the log should be
documented somewhere IMO.

Of course, that applies to the functions below as well.

> +
> +static __init int hmat_parse_cache(union acpi_subtable_headers *header,
> +                                  const unsigned long end)
> +{
> +       struct acpi_hmat_cache *cache = (void *)header;
> +       u32 attrs;
> +
> +       if (cache->header.length < sizeof(*cache)) {
> +               pr_err("HMAT: Unexpected cache header length: %d\n",
> +                       cache->header.length);
> +               return -EINVAL;
> +       }
> +
> +       attrs = cache->cache_attributes;
> +       pr_info("HMAT: Cache: Domain:%d Size:%llu Attrs:%08x SMBIOS Handles:%d\n",
> +               cache->memory_PD, cache->cache_size, attrs,
> +               cache->number_of_SMBIOShandles);
> +
> +       return 0;
> +}
> +
> +static int __init hmat_parse_address_range(union acpi_subtable_headers *header,
> +                                          const unsigned long end)
> +{
> +       struct acpi_hmat_address_range *spa = (void *)header;
> +
> +       if (spa->header.length != sizeof(*spa)) {
> +               pr_err("HMAT: Unexpected address range header length: %d\n",
> +                       spa->header.length);
> +               return -EINVAL;
> +       }
> +       pr_info("HMAT: Memory (%#llx length %#llx) Flags:%04x Processor Domain:%d Memory Domain:%d\n",
> +               spa->physical_address_base, spa->physical_address_length,
> +               spa->flags, spa->processor_PD, spa->memory_PD);
> +       return 0;
> +}
> +
> +static int __init hmat_parse_subtable(union acpi_subtable_headers *header,
> +                                     const unsigned long end)
> +{
> +       struct acpi_hmat_structure *hdr = (void *)header;
> +
> +       if (!hdr)
> +               return -EINVAL;
> +
> +       switch (hdr->type) {
> +       case ACPI_HMAT_TYPE_ADDRESS_RANGE:
> +               return hmat_parse_address_range(header, end);
> +       case ACPI_HMAT_TYPE_LOCALITY:
> +               return hmat_parse_locality(header, end);
> +       case ACPI_HMAT_TYPE_CACHE:
> +               return hmat_parse_cache(header, end);
> +       default:
> +               return -EINVAL;
> +       }
> +}
> +
> +static __init int hmat_init(void)
> +{
> +       struct acpi_table_header *tbl;
> +       enum acpi_hmat_type i;
> +       acpi_status status;
> +
> +       if (srat_disabled())
> +               return 0;
> +
> +       status = acpi_get_table(ACPI_SIG_HMAT, 0, &tbl);
> +       if (ACPI_FAILURE(status))
> +               return 0;
> +
> +       for (i = ACPI_HMAT_TYPE_ADDRESS_RANGE; i < ACPI_HMAT_TYPE_RESERVED; i++) {
> +               if (acpi_table_parse_entries(ACPI_SIG_HMAT,
> +                                            sizeof(struct acpi_table_hmat), i,
> +                                            hmat_parse_subtable, 0) < 0)
> +                       goto out_put;
> +       }
> +out_put:
> +       acpi_put_table(tbl);
> +       return 0;
> +}
> +subsys_initcall(hmat_init);
> --

It looks like this particular patch only causes some extra messages to
be printed into the log, no attributes setting etc yet.

I would like the changelog to mention that.