powerpc/mm: Warn on flushing tlb page in kernel context

Function __flush_tlb_page() must only be called for user contexts, so
put in extra hardening to warn on calling it for kernel context.

Signed-off-by: Arseny Solokha <asolokha@kb.kras.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c
index ab0616b0e6c2..cbd3d069897f 100644
--- a/arch/powerpc/mm/tlb_nohash.c
+++ b/arch/powerpc/mm/tlb_nohash.c
@@ -284,7 +284,11 @@ void __flush_tlb_page(struct mm_struct *mm, unsigned long vmaddr,
         struct cpumask *cpu_mask;
         unsigned int pid;
 
-        if (unlikely(!mm))
+        /*
+         * This function as well as __local_flush_tlb_page() must only be called
+         * for user contexts.
+         */
+        if (unlikely(WARN_ON(!mm)))
                 return;
 
         preempt_disable();