powerpc: cleanup AMR, IAMR when a key is allocated or freed

Cleanup the bits corresponding to a key in the AMR, and IAMR
register, when the key is newly allocated/activated or is freed.
We dont want some residual bits cause the hardware enforce
unintended behavior when the key is activated or freed.

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/pkeys.h

@@ -58,6 +58,8 @@ static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
 		__mm_pkey_is_allocated(mm, pkey));
 }
 
+extern void __arch_activate_pkey(int pkey);
+extern void __arch_deactivate_pkey(int pkey);
 /*
  * Returns a positive, 5-bit key on success, or -1 on failure.
  * Relies on the mmap_sem to protect against concurrency in mm_pkey_alloc() and
@@ -85,6 +87,12 @@ static inline int mm_pkey_alloc(struct mm_struct *mm)
 
 	ret = ffz((u32)mm_pkey_allocation_map(mm));
 	__mm_pkey_allocated(mm, ret);
+
+	/*
+	 * Enable the key in the hardware
+	 */
+	if (ret > 0)
+		__arch_activate_pkey(ret);
 	return ret;
 }
 
@@ -96,6 +104,10 @@ static inline int mm_pkey_free(struct mm_struct *mm, int pkey)
 	if (!mm_pkey_is_allocated(mm, pkey))
 		return -EINVAL;
 
+	/*
+	 * Disable the key in the hardware
+	 */
+	__arch_deactivate_pkey(pkey);
 	__mm_pkey_free(mm, pkey);
 
 	return 0;