[PATCH 1/2] arm64: mm: Restore mm_cpumask (revert commit 38d96287504a ("arm64: mm: kill mm_cpumask usage"))

[Takao Indoh <indou.takao@jp.fujitsu.com>]

From: Takao Indoh <indou.takao@fujitsu.com>

mm_cpumask was deleted by the commit 38d96287504a ("arm64: mm: kill
mm_cpumask usage") because it was not used at that time. Now this is needed
to find appropriate CPUs for TLB flush, so this patch reverts this commit.

Signed-off-by: QI Fuli <qi.fuli@fujitsu.com>
Signed-off-by: Takao Indoh <indou.takao@fujitsu.com>
---
 arch/arm64/include/asm/mmu_context.h | 7 ++++++-
 arch/arm64/kernel/smp.c              | 6 ++++++
 arch/arm64/mm/context.c              | 2 ++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 2da3e478fd8f..21ef11590bcb 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -241,8 +241,13 @@ static inline void
 switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	  struct task_struct *tsk)
 {
-	if (prev != next)
+	unsigned int cpu = smp_processor_id();
+
+	if (prev != next) {
 		__switch_mm(next);
+		cpumask_clear_cpu(cpu, mm_cpumask(prev));
+		local_flush_tlb_mm(prev);
+	}
 
 	/*
 	 * Update the saved TTBR0_EL1 of the scheduled-in task as the previous
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index bb4b3f07761a..12a922d1cdd7 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -218,6 +218,7 @@ asmlinkage notrace void secondary_start_kernel(void)
 	 */
 	mmgrab(mm);
 	current->active_mm = mm;
+	cpumask_set_cpu(cpu, mm_cpumask(mm));
 
 	/*
 	 * TTBR0 is only used for the identity mapping at this stage. Make it
@@ -320,6 +321,11 @@ int __cpu_disable(void)
 	 */
 	irq_migrate_all_off_this_cpu();
 
+	/*
+	 * Remove this CPU from the vm mask set of all processes.
+	 */
+	clear_tasks_mm_cpumask(cpu);
+
 	return 0;
 }
 
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index 1f0ea2facf24..ff3ab2924074 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -188,6 +188,7 @@ static u64 new_context(struct mm_struct *mm)
 set_asid:
 	__set_bit(asid, asid_map);
 	cur_idx = asid;
+	cpumask_clear(mm_cpumask(mm));
 	return idx2asid(asid) | generation;
 }
 
@@ -239,6 +240,7 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu)
 switch_mm_fastpath:
 
 	arm64_apply_bp_hardening();
+	cpumask_set_cpu(cpu, mm_cpumask(mm));
 
 	/*
 	 * Defer TTBR0_EL1 setting for user threads to uaccess_enable() when
-- 
2.20.1