Messages in this thread | | | From | Will Deacon <> | Subject | [PATCH v5 00/15] An alternative series for asymmetric AArch32 systems | Date | Tue, 8 Dec 2020 13:28:20 +0000 |
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Hi all,
Christmas has come early: it's time for version five of these patches which have previously appeared here:
v1: https://lore.kernel.org/r/20201027215118.27003-1-will@kernel.org v2: https://lore.kernel.org/r/20201109213023.15092-1-will@kernel.org v3: https://lore.kernel.org/r/20201113093720.21106-1-will@kernel.org v4: https://lore.kernel.org/r/20201124155039.13804-1-will@kernel.org
and which started life as a reimplementation of some patches from Qais:
https://lore.kernel.org/r/20201021104611.2744565-1-qais.yousef@arm.com
There's also now a nice writeup on LWN:
https://lwn.net/Articles/838339/
and rumours of a feature film are doing the rounds.
[subscriber-only, but if you're reading this then you should really subscribe.]
The aim of this series is to allow 32-bit ARM applications to run on arm64 SoCs where not all of the CPUs support the 32-bit instruction set. Unfortunately, such SoCs are real and will continue to be productised over the next few years at least. I can assure you that I'm not just doing this for fun.
Changes in v5 include:
* Teach cpuset_cpus_allowed() about task_cpu_possible_mask() so that we can avoid returning incompatible CPUs for a given task. This means that sched_setaffinity() can be used with larger masks (like the online mask) from userspace and also allows us to take into account the cpuset hierarchy when forcefully overriding the affinity for a task on execve().
* Honour task_cpu_possible_mask() when attaching a task to a cpuset, so that the resulting affinity mask does not contain any incompatible CPUs (since it would be rejected by set_cpus_allowed_ptr() otherwise).
* Moved overriding of the affinity mask into the scheduler core rather than munge affinity masks directly in the architecture backend.
* Extended comments and documentation.
* Some renaming and cosmetic changes.
I'm pretty happy with this now, although it still needs review and will require rebasing to play nicely with the SCA changes in -next.
Cheers,
Will
Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Qais Yousef <qais.yousef@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Quentin Perret <qperret@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: kernel-team@android.com
--->8
Will Deacon (15): 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 force_compatible_cpus_allowed_ptr() to limit CPU 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: Hook up cmdline parameter to allow mismatched 32-bit EL0 arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores
.../ABI/testing/sysfs-devices-system-cpu | 9 + .../admin-guide/kernel-parameters.txt | 8 + arch/arm64/include/asm/cpu.h | 44 ++-- arch/arm64/include/asm/cpucaps.h | 3 +- arch/arm64/include/asm/cpufeature.h | 8 +- arch/arm64/include/asm/mmu_context.h | 13 ++ arch/arm64/kernel/cpufeature.c | 219 ++++++++++++++---- arch/arm64/kernel/cpuinfo.c | 53 +++-- arch/arm64/kernel/process.c | 19 +- arch/arm64/kvm/arm.c | 11 +- include/linux/cpuset.h | 3 +- include/linux/mmu_context.h | 8 + include/linux/sched.h | 1 + kernel/cgroup/cpuset.c | 39 ++-- kernel/sched/core.c | 112 +++++++-- 15 files changed, 426 insertions(+), 124 deletions(-)
-- 2.29.2.576.ga3fc446d84-goog
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