arm64: mm: kill mm_cpumask usage

mm_cpumask isn't actually used for anything on arm64, so remove all the
code trying to keep it up-to-date.
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/smp.c

@@ -142,7 +142,6 @@ asmlinkage void secondary_start_kernel(void)
 	 */
 	atomic_inc(&mm->mm_count);
 	current->active_mm = mm;
-	cpumask_set_cpu(cpu, mm_cpumask(mm));
 
 	set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
 	printk("CPU%u: Booted secondary processor\n", cpu);
@@ -233,12 +232,6 @@ int __cpu_disable(void)
 	 * OK - migrate IRQs away from this CPU
 	 */
 	migrate_irqs();
-
-	/*
-	 * Remove this CPU from the vm mask set of all processes.
-	 */
-	clear_tasks_mm_cpumask(cpu);
-
 	return 0;
 }
 

arch/arm64/mm/context.c

@@ -132,7 +132,6 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu)
 
 bump_gen:
 	asid |= generation;
-	cpumask_clear(mm_cpumask(mm));
 	return asid;
 }
 
@@ -169,7 +168,6 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu)
 	raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
 
 switch_mm_fastpath:
-	cpumask_set_cpu(cpu, mm_cpumask(mm));
 	cpu_switch_mm(mm->pgd, mm);
 }