| Message ID | 20210518094725.7701-18-will@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add support for 32-bit tasks on asymmetric AArch32 systems | expand |
On Tue, May 18, 2021 at 10:47:21AM +0100, Will Deacon wrote: > 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. > > Similarly, when exec'ing a 64-bit task on such a system, try to restore > the old affinity mask if it was previously restricted. > > Reviewed-by: Quentin Perret <qperret@google.com> > Signed-off-by: Will Deacon <will@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index f4a91bf1ce0c..8e0da06c4e77 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -647,8 +647,22 @@ 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); + } + } else if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) { + relax_compatible_cpus_allowed_ptr(current); } current->mm->context.flags = mmflags;