[PATCH v11 00/16] Add support for 32-bit tasks on asymmetric AArch32 systems

[Will Deacon]

Hi everyone,

This is version eleven of the patches previously posted here:

  v1: https://lore.kernel.org/r/20201027215118.27003-1-will@xxxxxxxxxx
  v2: https://lore.kernel.org/r/20201109213023.15092-1-will@xxxxxxxxxx
  v3: https://lore.kernel.org/r/20201113093720.21106-1-will@xxxxxxxxxx
  v4: https://lore.kernel.org/r/20201124155039.13804-1-will@xxxxxxxxxx
  v5: https://lore.kernel.org/r/20201208132835.6151-1-will@xxxxxxxxxx
  v6: https://lore.kernel.org/r/20210518094725.7701-1-will@xxxxxxxxxx
  v7: https://lore.kernel.org/r/20210525151432.16875-1-will@xxxxxxxxxx
  v8: https://lore.kernel.org/r/20210602164719.31777-1-will@xxxxxxxxxx
  v9: https://lore.kernel.org/r/20210608180313.11502-1-will@xxxxxxxxxx
 v10: https://lore.kernel.org/r/20210623173848.318-1-will@xxxxxxxxxx

The main changes since v10 are:

  * Now based on v5.14-rc1

  * Fixed a lockup found during testing where select_fallback_rq()
    could return an invalid CPU when trying to prioritise a destination
    on the same NUMA node

Greg kindly pointed out a potential issue with the new 'aarch32_el0'
file in sysfs, where the contents will be truncated if we need to
display more than a PAGE_SIZE of data. However, I have elected not to
address this for now as (a) I do not think we'll ever have hardware in
that configuration (yeah, I know...) and (b) It is useful for scripts
if the file behaves the same as the other files in the same directory
(e.g. 'online'). Should a solution to this problem emerge for the other
files, I will be happy to adopt it here as well.

This series is now mostly scheduler stuff, but the last few patches are
arm64 and so I would suggest a shared branch in -tip for merging.

Cheers,

Will

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Morten Rasmussen <morten.rasmussen@xxxxxxx>
Cc: Qais Yousef <qais.yousef@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Quentin Perret <qperret@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Valentin Schneider <valentin.schneider@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: kernel-team@xxxxxxxxxxx

--->8

Will Deacon (16):
  sched: Introduce task_cpu_possible_mask() to limit fallback rq
    selection
  cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1
  cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus()
  cpuset: Cleanup cpuset_cpus_allowed_fallback() use in
    select_fallback_rq()
  sched: Reject CPU affinity changes based on task_cpu_possible_mask()
  sched: Introduce task_struct::user_cpus_ptr to track requested
    affinity
  sched: Split the guts of sched_setaffinity() into a helper function
  sched: Allow task CPU affinity to be restricted on asymmetric systems
  sched: Introduce dl_task_check_affinity() to check proposed affinity
  arm64: Implement task_cpu_possible_mask()
  arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit
    EL0
  arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched
    system
  arm64: Advertise CPUs capable of running 32-bit applications in sysfs
  arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0
  arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores
  Documentation: arm64: describe asymmetric 32-bit support

 .../ABI/testing/sysfs-devices-system-cpu      |   9 +
 .../admin-guide/kernel-parameters.txt         |  11 +
 Documentation/arm64/asymmetric-32bit.rst      | 155 ++++++++
 Documentation/arm64/index.rst                 |   1 +
 arch/arm64/include/asm/elf.h                  |   6 +-
 arch/arm64/include/asm/mmu_context.h          |  13 +
 arch/arm64/kernel/cpufeature.c                |  51 ++-
 arch/arm64/kernel/process.c                   |  47 ++-
 arch/arm64/kernel/signal.c                    |  26 --
 include/linux/cpuset.h                        |   8 +-
 include/linux/mmu_context.h                   |  14 +
 include/linux/sched.h                         |  21 ++
 init/init_task.c                              |   1 +
 kernel/cgroup/cpuset.c                        |  59 ++-
 kernel/fork.c                                 |   2 +
 kernel/sched/core.c                           | 344 ++++++++++++++----
 kernel/sched/sched.h                          |   1 +
 17 files changed, 628 insertions(+), 141 deletions(-)
 create mode 100644 Documentation/arm64/asymmetric-32bit.rst

-- 
2.32.0.402.g57bb445576-goog