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Date: Tue, 8 Dec 2020 13:28:32 +0000 From: Will Deacon <will@...nel.org> To: linux-arm-kernel@...ts.infradead.org Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, Will Deacon <will@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Peter Zijlstra <peterz@...radead.org>, Morten Rasmussen <morten.rasmussen@....com>, Qais Yousef <qais.yousef@....com>, Suren Baghdasaryan <surenb@...gle.com>, Quentin Perret <qperret@...gle.com>, Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>, Johannes Weiner <hannes@...xchg.org>, Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, kernel-team@...roid.com Subject: [PATCH v5 12/15] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 When exec'ing a 32-bit task on a system with mismatched support for 32-bit EL0, try to ensure that it starts life on a CPU that can actually run it. Reviewed-by: Quentin Perret <qperret@...gle.com> Signed-off-by: Will Deacon <will@...nel.org> --- arch/arm64/kernel/process.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 9a2532d848f0..da313b738c7c 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -633,8 +633,20 @@ void arch_setup_new_exec(void) if (is_compat_task()) { mmflags = MMCF_AARCH32; - if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) + + /* + * Restrict the CPU affinity mask for a 32-bit task so that + * it contains only 32-bit-capable CPUs. + * + * From the perspective of the task, this looks similar to + * what would happen if the 64-bit-only CPUs were hot-unplugged + * at the point of execve(), although we try a bit harder to + * honour the cpuset hierarchy. + */ + if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) { + force_compatible_cpus_allowed_ptr(current); set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); + } } current->mm->context.flags = mmflags; -- 2.29.2.576.ga3fc446d84-goog
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