From: Valentin Schneider <valentin.schneider@arm•com>
To: Will Deacon <will@kernel•org>, linux-arm-kernel@lists•infradead.org
Cc: linux-arch@vger•kernel.org, linux-kernel@vger•kernel.org,
Will Deacon <will@kernel•org>,
Catalin Marinas <catalin.marinas@arm•com>,
Marc Zyngier <maz@kernel•org>,
Greg Kroah-Hartman <gregkh@linuxfoundation•org>,
Peter Zijlstra <peterz@infradead•org>,
Morten Rasmussen <morten.rasmussen@arm•com>,
Qais Yousef <qais.yousef@arm•com>,
Suren Baghdasaryan <surenb@google•com>,
Quentin Perret <qperret@google•com>, Tejun Heo <tj@kernel•org>,
Johannes Weiner <hannes@cmpxchg•org>,
Ingo Molnar <mingo@redhat•com>,
Juri Lelli <juri.lelli@redhat•com>,
Vincent Guittot <vincent.guittot@linaro•org>,
"Rafael J. Wysocki" <rjw@rjwysocki•net>,
Dietmar Eggemann <dietmar.eggemann@arm•com>,
Daniel Bristot de Oliveira <bristot@redhat•com>,
Mark Rutland <mark.rutland@arm•com>,
kernel-team@android•com
Subject: Re: [PATCH v9 12/20] sched: Allow task CPU affinity to be restricted on asymmetric systems
Date: Thu, 10 Jun 2021 14:00:03 +0100 [thread overview]
Message-ID: <875yyldgdo.mognet@arm.com> (raw)
In-Reply-To: <20210608180313.11502-13-will@kernel.org>
On 08/06/21 19:03, Will Deacon wrote:
> Asymmetric systems may not offer the same level of userspace ISA support
> across all CPUs, meaning that some applications cannot be executed by
> some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do
> not feature support for 32-bit applications on both clusters.
>
> Although userspace can carefully manage the affinity masks for such
> tasks, one place where it is particularly problematic is execve()
> because the CPU on which the execve() is occurring may be incompatible
> with the new application image. In such a situation, it is desirable to
> restrict the affinity mask of the task and ensure that the new image is
> entered on a compatible CPU. From userspace's point of view, this looks
> the same as if the incompatible CPUs have been hotplugged off in the
> task's affinity mask. Similarly, if a subsequent execve() reverts to
> a compatible image, then the old affinity is restored if it is still
> valid.
>
> In preparation for restricting the affinity mask for compat tasks on
> arm64 systems without uniform support for 32-bit applications, introduce
> {force,relax}_compatible_cpus_allowed_ptr(), which respectively restrict
> and restore the affinity mask for a task based on the compatible CPUs.
>
> Reviewed-by: Quentin Perret <qperret@google•com>
> Signed-off-by: Will Deacon <will@kernel•org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm•com>
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next prev parent reply other threads:[~2021-06-10 13:02 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 18:02 [PATCH v9 00/20] Add support for 32-bit tasks on asymmetric AArch32 systems Will Deacon
2021-06-08 18:02 ` [PATCH v9 01/20] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2021-06-08 18:02 ` [PATCH v9 02/20] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2021-06-08 18:02 ` [PATCH v9 03/20] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2021-06-08 18:02 ` [PATCH v9 04/20] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2021-06-08 18:02 ` [PATCH v9 05/20] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon
2021-06-08 18:02 ` [PATCH v9 06/20] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2021-06-10 12:59 ` Valentin Schneider
2021-06-08 18:03 ` [PATCH v9 07/20] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon
2021-06-08 18:03 ` [PATCH v9 08/20] cpuset: Cleanup cpuset_cpus_allowed_fallback() use in select_fallback_rq() Will Deacon
2021-06-10 12:59 ` Valentin Schneider
2021-06-08 18:03 ` [PATCH v9 09/20] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon
2021-06-08 18:03 ` [PATCH v9 10/20] sched: Introduce task_struct::user_cpus_ptr to track requested affinity Will Deacon
2021-06-08 18:03 ` [PATCH v9 11/20] sched: Split the guts of sched_setaffinity() into a helper function Will Deacon
2021-06-08 18:03 ` [PATCH v9 12/20] sched: Allow task CPU affinity to be restricted on asymmetric systems Will Deacon
2021-06-10 13:00 ` Valentin Schneider [this message]
2021-06-08 18:03 ` [PATCH v9 13/20] sched: Introduce dl_task_check_affinity() to check proposed affinity Will Deacon
2021-06-08 18:03 ` [PATCH v9 14/20] arm64: Implement task_cpu_possible_mask() Will Deacon
2021-06-08 18:03 ` [PATCH v9 15/20] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2021-06-08 18:03 ` [PATCH v9 16/20] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2021-06-08 18:03 ` [PATCH v9 17/20] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2021-06-08 18:03 ` [PATCH v9 18/20] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2021-06-08 18:03 ` [PATCH v9 19/20] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2021-06-08 18:03 ` [PATCH v9 20/20] Documentation: arm64: describe asymmetric 32-bit support Will Deacon
2021-06-11 16:15 ` [PATCH v9 00/20] Add support for 32-bit tasks on asymmetric AArch32 systems Will Deacon
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