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    Subject[PATCH RESEND v3 0/6] arm64: add the time namespace support
    Date
    Allocate the time namespace page among VVAR pages and add the logic
    to handle faults on VVAR properly.

    If a task belongs to a time namespace then the VVAR page which contains
    the system wide VDSO data is replaced with a namespace specific page
    which has the same layout as the VVAR page. That page has vdso_data->seq
    set to 1 to enforce the slow path and vdso_data->clock_mode set to
    VCLOCK_TIMENS to enforce the time namespace handling path.

    The extra check in the case that vdso_data->seq is odd, e.g. a concurrent
    update of the VDSO data is in progress, is not really affecting regular
    tasks which are not part of a time namespace as the task is spin waiting
    for the update to finish and vdso_data->seq to become even again.

    If a time namespace task hits that code path, it invokes the corresponding
    time getter function which retrieves the real VVAR page, reads host time
    and then adds the offset for the requested clock which is stored in the
    special VVAR page.

    v2: Code cleanups suggested by Vincenzo.
    v3: add a comment in __arch_get_timens_vdso_data.

    Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Dmitry Safonov <dima@arista.com>

    v3 on github (if someone prefers `git pull` to `git am`):
    https://github.com/avagin/linux-task-diag/tree/arm64/timens-v3

    Andrei Vagin (6):
    arm64/vdso: use the fault callback to map vvar pages
    arm64/vdso: Zap vvar pages when switching to a time namespace
    arm64/vdso: Add time napespace page
    arm64/vdso: Handle faults on timens page
    arm64/vdso: Restrict splitting VVAR VMA
    arm64: enable time namespace support

    arch/arm64/Kconfig | 1 +
    .../include/asm/vdso/compat_gettimeofday.h | 11 ++
    arch/arm64/include/asm/vdso/gettimeofday.h | 8 ++
    arch/arm64/kernel/vdso.c | 134 ++++++++++++++++--
    arch/arm64/kernel/vdso/vdso.lds.S | 3 +-
    arch/arm64/kernel/vdso32/vdso.lds.S | 3 +-
    include/vdso/datapage.h | 1 +
    7 files changed, 147 insertions(+), 14 deletions(-)

    --
    2.24.1

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