powerpc/book3s64/pkeys: Explain key 1 reservation details

This explains the details w.r.t key 1.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709032946.881753-6-aneesh.kumar@linux.ibm.com

diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index 82ace6a..ee27f18 100644 (file)
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/arch/powerpc/mm/book3s64/pkeys.c
@@ -128,7 +128,10 @@ static int pkey_initialize(void)
 #else
        os_reserved = 0;
 #endif
-       /* Bits are in LE format. */
+       /*
+        * key 1 is recommended not to be used. PowerISA(3.0) page 1015,
+        * programming note.
+        */
        reserved_allocation_mask = (0x1 << 1) | (0x1 << execute_only_key);
 
        /* register mask is in BE format */