powerpc fixes for 6.4 #5

- Disable IRQs when switching mm in exit_lazy_flush_tlb() called from exit_mmap()
 
 Thanks to: Nicholas Piggin, Sachin Sant.
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Merge tag 'powerpc-6.4-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fix from Michael Ellerman:

 - Disable IRQs when switching mm in exit_lazy_flush_tlb() called from
   exit_mmap()

Thanks to Nicholas Piggin and Sachin Sant.

* tag 'powerpc-6.4-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/64s/radix: Fix exit lazy tlb mm switch with irqs enabled

arch/powerpc/mm/book3s64/radix_tlb.c

@@ -795,12 +795,20 @@ void exit_lazy_flush_tlb(struct mm_struct *mm, bool always_flush)
 		goto out;
 
 	if (current->active_mm == mm) {
+		unsigned long flags;
+
 		WARN_ON_ONCE(current->mm != NULL);
-		/* Is a kernel thread and is using mm as the lazy tlb */
+		/*
+		 * It is a kernel thread and is using mm as the lazy tlb, so
+		 * switch it to init_mm. This is not always called from IPI
+		 * (e.g., flush_type_needed), so must disable irqs.
+		 */
+		local_irq_save(flags);
 		mmgrab_lazy_tlb(&init_mm);
 		current->active_mm = &init_mm;
 		switch_mm_irqs_off(mm, &init_mm, current);
 		mmdrop_lazy_tlb(mm);
+		local_irq_restore(flags);
 	}
 
 	/*