[PATCH v7 00/22] Add support for 32-bit tasks on asymmetric AArch32 systems

From: Will Deacon
Date: Tue May 25 2021 - 11:15:20 EST


Hi all,

Here is v7 of the asymmetric 32-bit support patches that I 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

There was also a nice LWN writeup in case you've forgotten what this is
about:

https://lwn.net/Articles/838339/

Changes since v6 include:

* Bug fix for a pre-existing scheduler migration bug spotted by
Valentin (nice work!). I've put this patch at the start.

* Prevent execve() of a 32-bit program from a 64-bit deadline task if
the forced affinity would violate admission control

* Fixed a memory leak and missing rcu_read_lock() spotted by Qais
(thanks!)

* Handle race between forcing affinity on execve() and CPU hot-unplug

* Updated documentation

* Introduce task_cpu_possible() macro as suggested by Peter Z

* Added some acks/reviewed-by tags, although I didn't include these
where patches have changed significantly since last time.

Series now based on v5.13-rc3 to avoid conflicting with arm64 cpucaps
rework merged at -rc2.

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: kernel-team@xxxxxxxxxxx

--->8

Will Deacon (22):
sched: Favour predetermined active CPU as migration destination
arm64: cpuinfo: Split AArch32 registers out into a separate struct
arm64: Allow mismatched 32-bit EL0 support
KVM: arm64: Kill 32-bit vCPUs on systems with mismatched EL0 support
arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs
arm64: Advertise CPUs capable of running 32-bit applications in sysfs
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()
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 task_cpus_dl_admissible() to check proposed affinity
freezer: Add frozen_or_skipped() helper function
sched: Defer wakeup in ttwu() for unschedulable frozen tasks
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: 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 | 154 ++++++++
Documentation/arm64/index.rst | 1 +
arch/arm64/include/asm/cpu.h | 44 ++-
arch/arm64/include/asm/cpufeature.h | 8 +-
arch/arm64/include/asm/elf.h | 6 +-
arch/arm64/include/asm/mmu_context.h | 13 +
arch/arm64/kernel/cpufeature.c | 227 ++++++++---
arch/arm64/kernel/cpuinfo.c | 53 +--
arch/arm64/kernel/process.c | 44 ++-
arch/arm64/kvm/arm.c | 11 +-
arch/arm64/tools/cpucaps | 3 +-
include/linux/cpuset.h | 3 +-
include/linux/freezer.h | 6 +
include/linux/mmu_context.h | 11 +
include/linux/sched.h | 21 ++
init/init_task.c | 1 +
kernel/cgroup/cpuset.c | 53 ++-
kernel/fork.c | 2 +
kernel/freezer.c | 10 +-
kernel/hung_task.c | 4 +-
kernel/sched/core.c | 351 ++++++++++++++----
kernel/sched/sched.h | 1 +
24 files changed, 850 insertions(+), 197 deletions(-)
create mode 100644 Documentation/arm64/asymmetric-32bit.rst

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2.31.1.818.g46aad6cb9e-goog