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    Subject[RFC PATCH 0/3] ACPI, arm64: Backport for ACPI PPTT 6.3 thread flag for stable 4.19.x
    Date
    This series is a backport of the ACPI PPTT 6.3 thread flag feature for
    supporting arm64 systems.

    The background is that some arm64 implementations are broken, in that they
    incorrectly advertise that a CPU is mutli-threaded, when it is not - the
    HiSilicon Taishanv110 rev 2, aka tsv110, being an example.

    This leads to the system topology being incorrect. The reason being that
    arm64 topology code uses a combination of ACPI PPTT (Processor Properties
    Topology Table) and the system MPIDR (Multiprocessor Affinity Register) MT
    bit to determine the topology.

    Until ACPI 6.3, the PPTT did not have any method to determine whether
    a CPU was multi-threaded, so only the MT bit is used - hence the
    broken topology for some systems.

    In ACPI 6.3, a PPTT thread flag was introduced, which - when supported -
    would be used by the kernel to determine really if a CPU is multi-threaded
    or not, so that we don't get incorrect topology.

    Note: I'm sending this as an RFC before sending to stable proper. I also
    have a 5.2 and 5.3 backport which are almost the same, and only
    significant change being that the ACPICA patch is not required.

    Erik Schmauss (1):
    ACPICA: ACPI 6.3: PPTT add additional fields in Processor Structure
    Flags

    Jeremy Linton (2):
    ACPI/PPTT: Add support for ACPI 6.3 thread flag
    arm64: topology: Use PPTT to determine if PE is a thread

    arch/arm64/kernel/topology.c | 19 ++++++++++---
    drivers/acpi/pptt.c | 52 ++++++++++++++++++++++++++++++++++++
    include/acpi/actbl2.h | 7 +++--
    include/linux/acpi.h | 5 ++++
    4 files changed, 77 insertions(+), 6 deletions(-)

    --
    2.17.1

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