1 files changed, 44 insertions, 15 deletions
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index a2becb85bea7..6cf881a942bb 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -607,18 +607,15 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next,
 		cond_mitigation(tsk);
 
 		/*
-		 * Stop remote flushes for the previous mm.
-		 * Skip kernel threads; we never send init_mm TLB flushing IPIs,
-		 * but the bitmap manipulation can cause cache line contention.
+		 * Leave this CPU in prev's mm_cpumask. Atomic writes to
+		 * mm_cpumask can be expensive under contention. The CPU
+		 * will be removed lazily at TLB flush time.
 		 */
-		if (prev != &init_mm) {
-			VM_WARN_ON_ONCE(!cpumask_test_cpu(cpu,
-						mm_cpumask(prev)));
-			cpumask_clear_cpu(cpu, mm_cpumask(prev));
-		}
+		VM_WARN_ON_ONCE(prev != &init_mm && !cpumask_test_cpu(cpu,
+				mm_cpumask(prev)));
 
 		/* Start receiving IPIs and then read tlb_gen (and LAM below) */
-		if (next != &init_mm)
+		if (next != &init_mm && !cpumask_test_cpu(cpu, mm_cpumask(next)))
 			cpumask_set_cpu(cpu, mm_cpumask(next));
 		next_tlb_gen = atomic64_read(&next->context.tlb_gen);
 
@@ -760,10 +757,13 @@ static void flush_tlb_func(void *info)
 	if (!local) {
 		inc_irq_stat(irq_tlb_count);
 		count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
+	}
 
-		/* Can only happen on remote CPUs */
-		if (f->mm && f->mm != loaded_mm)
-			return;
+	/* The CPU was left in the mm_cpumask of the target mm. Clear it. */
+	if (f->mm && f->mm != loaded_mm) {
+		cpumask_clear_cpu(raw_smp_processor_id(), mm_cpumask(f->mm));
+		trace_tlb_flush(TLB_REMOTE_WRONG_CPU, 0);
+		return;
 	}
 
 	if (unlikely(loaded_mm == &init_mm))
@@ -893,9 +893,36 @@ done:
 			nr_invalidate);
 }
 
-static bool tlb_is_not_lazy(int cpu, void *data)
+static bool should_flush_tlb(int cpu, void *data)
+{
+	struct flush_tlb_info *info = data;
+
+	/* Lazy TLB will get flushed at the next context switch. */
+	if (per_cpu(cpu_tlbstate_shared.is_lazy, cpu))
+		return false;
+
+	/* No mm means kernel memory flush. */
+	if (!info->mm)
+		return true;
+
+	/* The target mm is loaded, and the CPU is not lazy. */
+	if (per_cpu(cpu_tlbstate.loaded_mm, cpu) == info->mm)
+		return true;
+
+	/* In cpumask, but not the loaded mm? Periodically remove by flushing. */
+	if (info->trim_cpumask)
+		return true;
+
+	return false;
+}
+
+static bool should_trim_cpumask(struct mm_struct *mm)
 {
-	return !per_cpu(cpu_tlbstate_shared.is_lazy, cpu);
+	if (time_after(jiffies, READ_ONCE(mm->context.next_trim_cpumask))) {
+		WRITE_ONCE(mm->context.next_trim_cpumask, jiffies + HZ);
+		return true;
+	}
+	return false;
 }
 
 DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state_shared, cpu_tlbstate_shared);
@@ -929,7 +956,7 @@ STATIC_NOPV void native_flush_tlb_multi(const struct cpumask *cpumask,
 	if (info->freed_tables)
 		on_each_cpu_mask(cpumask, flush_tlb_func, (void *)info, true);
 	else
-		on_each_cpu_cond_mask(tlb_is_not_lazy, flush_tlb_func,
+		on_each_cpu_cond_mask(should_flush_tlb, flush_tlb_func,
 				(void *)info, 1, cpumask);
 }
 
@@ -980,6 +1007,7 @@ static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
 	info->freed_tables	= freed_tables;
 	info->new_tlb_gen	= new_tlb_gen;
 	info->initiating_cpu	= smp_processor_id();
+	info->trim_cpumask	= 0;
 
 	return info;
 }
@@ -1022,6 +1050,7 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
 	 * flush_tlb_func_local() directly in this case.
 	 */
 	if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids) {
+		info->trim_cpumask = should_trim_cpumask(mm);
 		flush_tlb_multi(mm_cpumask(mm), info);
 	} else if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) {
 		lockdep_assert_irqs_enabled();