apply_to_page_range on kernel pages does not disable preemption, which
is a requirement for hash's lazy mmu mode, which keeps track of the
TLBs to flush with a per-cpu array.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
  arch/powerpc/include/asm/book3s/64/tlbflush-hash.h | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
index fab8332fe1ad..751921f6db46 100644
--- a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
+++ b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h

@@ -32,6 +32,11 @@ static inline void arch_enter_lazy_mmu_mode(void)
  
  	if (radix_enabled())
  		return;
+	/*
+	 * apply_to_page_range can call us this preempt enabled when
+	 * operating on kernel page tables.
+	 */
+	preempt_disable();
  	batch = this_cpu_ptr(&ppc64_tlb_batch);
  	batch->active = 1;
  }

@@ -47,6 +52,7 @@ static inline void arch_leave_lazy_mmu_mode(void)
  	if (batch->index)
  		__flush_tlb_pending(batch);
  	batch->active = 0;
+	preempt_enable();