diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
index 64201125a287..d4b145b279f6 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h
@@ -4,6 +4,8 @@
 
 #include <asm/bug.h>
 #include <asm/book3s/32/mmu-hash.h>
+#include <asm/mmu.h>
+#include <asm/synch.h>
 
 #ifndef __ASSEMBLY__
 
@@ -28,6 +30,15 @@ static inline void kuep_lock(void)
 		return;
 
 	update_user_segments(mfsr(0) | SR_NX);
+	/*
+	 * This isync() shouldn't be necessary as the kernel is not excepted to
+	 * run any instruction in userspace soon after the update of segments,
+	 * but hash based cores (at least G3) seem to exhibit a random
+	 * behaviour when the 'isync' is not there. 603 cores don't have this
+	 * behaviour so don't do the 'isync' as it saves several CPU cycles.
+	 */
+	if (mmu_has_feature(MMU_FTR_HPTE_TABLE))
+		isync();	/* Context sync required after mtsr() */
 }
 
 static inline void kuep_unlock(void)
@@ -36,6 +47,15 @@ static inline void kuep_unlock(void)
 		return;
 
 	update_user_segments(mfsr(0) & ~SR_NX);
+	/*
+	 * This isync() shouldn't be necessary as a 'rfi' will soon be executed
+	 * to return to userspace, but hash based cores (at least G3) seem to
+	 * exhibit a random behaviour when the 'isync' is not there. 603 cores
+	 * don't have this behaviour so don't do the 'isync' as it saves several
+	 * CPU cycles.
+	 */
+	if (mmu_has_feature(MMU_FTR_HPTE_TABLE))
+		isync();	/* Context sync required after mtsr() */
 }
 
 #ifdef CONFIG_PPC_KUAP