[PATCH v8 13/19] arm64: Implement task_cpu_possible_mask()

Will Deacon
2021-06-02T16:56:18Z

Provide an implementation of task_cpu_possible_mask() so that we can
prevent 64-bit-only cores being added to the 'cpus_mask' for compat
tasks on systems with mismatched 32-bit support at EL0,

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/mmu_context.h | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index d3cef9133539..bb9b7510f334 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -231,6 +231,19 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
update_saved_ttbr0(tsk, next);
}

+static inline const struct cpumask *
+task_cpu_possible_mask(struct task_struct *p)
+{
+ if (!static_branch_unlikely(&arm64_mismatched_32bit_el0))
+ return cpu_possible_mask;
+
+ if (!is_compat_thread(task_thread_info(p)))
+ return cpu_possible_mask;
+
+ return system_32bit_el0_cpumask();
+}
+#define task_cpu_possible_mask task_cpu_possible_mask
+
void verify_cpu_asid_bits(void);
void post_ttbr_update_workaround(void);

--
2.32.0.rc0.204.g9fa02ecfa5-goog