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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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