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SubjectRe: [PATCHv2 02/12] acpi/hmat: Parse and report heterogeneous memory
On Mon, Dec 10, 2018 at 5:05 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 | 8 +++
> drivers/acpi/Makefile | 1 +
> drivers/acpi/hmat.c | 192 ++++++++++++++++++++++++++++++++++++++++++++++++++
> drivers/acpi/tables.c | 9 +++
> include/linux/acpi.h | 1 +
> 5 files changed, 211 insertions(+)
> create mode 100644 drivers/acpi/hmat.c
>
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index 7cea769c37df..9a05af3a18cf 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -327,6 +327,14 @@ config ACPI_NUMA
> depends on (X86 || IA64 || ARM64)
> default y if IA64_GENERIC || IA64_SGI_SN2 || ARM64
>
> +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.
> +
> config ACPI_CUSTOM_DSDT_FILE
> string "Custom DSDT Table file to include"
> default ""
> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> index edc039313cd6..b5e13499f88b 100644
> --- a/drivers/acpi/Makefile
> +++ b/drivers/acpi/Makefile
> @@ -55,6 +55,7 @@ acpi-$(CONFIG_X86) += x86/apple.o
> acpi-$(CONFIG_X86) += x86/utils.o
> acpi-$(CONFIG_DEBUG_FS) += debugfs.o
> acpi-$(CONFIG_ACPI_NUMA) += numa.o
> +acpi-$(CONFIG_ACPI_HMAT) += hmat.o
> acpi-$(CONFIG_ACPI_PROCFS_POWER) += cm_sbs.o
> acpi-y += acpi_lpat.o
> acpi-$(CONFIG_ACPI_LPIT) += acpi_lpit.o
> diff --git a/drivers/acpi/hmat.c b/drivers/acpi/hmat.c
> new file mode 100644
> index 000000000000..ef3881f0f370
> --- /dev/null
> +++ b/drivers/acpi/hmat.c
[..]
> +static __init int hmat_init(void)
> +{
> + struct acpi_subtable_proc subtable_proc;
> + 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;
> +
> + if (acpi_table_parse(ACPI_SIG_HMAT, parse_noop))
> + goto out_put;
> +
> + memset(&subtable_proc, 0, sizeof(subtable_proc));
> + subtable_proc.handler = hmat_parse_subtable;
> + for (i = ACPI_HMAT_TYPE_ADDRESS_RANGE; i < ACPI_HMAT_TYPE_RESERVED; i++) {
> + subtable_proc.id = i;
> + if (acpi_table_parse_entries_array(ACPI_SIG_HMAT,
> + sizeof(struct acpi_table_hmat),
> + &subtable_proc, 1, 0) < 0)
> + goto out_put;
> + }
> + out_put:
> + acpi_put_table(tbl);
> + return 0;
> +}
> +subsys_initcall(hmat_init);

I have a use case to detect the presence of a memory-side-cache early
at init time [1]. To me this means that hmat_init() needs to happen as
a part of acpi_numa_init(). Subsequently I think that also means that
the sysfs portion needs to be broken out to its own init path that can
probably run at module_init() priority.

Perhaps we should split this patch set into two? The table parsing
with an in-kernel user is a bit easier to reason about and can go in
first. Towards that end can I steal / refllow patches 1 & 2 into the
memory randomization series? Other ideas how to handle this?

[1]: https://lkml.org/lkml/2018/10/12/309

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