On 02/21/2018 03:52 PM, Ram Pai wrote: > diff --git a/include/linux/mm.h b/include/linux/mm.h > index ad207ad..d534f46 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -231,9 +231,10 @@ extern int overcommit_kbytes_handler(struct ctl_table *, > int, void __user *, > #ifdef CONFIG_ARCH_HAS_PKEYS > # define VM_PKEY_SHIFT VM_HIGH_ARCH_BIT_0 > # define VM_PKEY_BIT0 VM_HIGH_ARCH_0 /* A protection key is a 4-bit > value */ > -# define VM_PKEY_BIT1 VM_HIGH_ARCH_1 > +# define VM_PKEY_BIT1 VM_HIGH_ARCH_1 /* on x86 and 5-bit value on > ppc64 */ > # define VM_PKEY_BIT2 VM_HIGH_ARCH_2 > # define VM_PKEY_BIT3 VM_HIGH_ARCH_3 > +# define VM_PKEY_BIT4 VM_HIGH_ARCH_4 > #endif /* CONFIG_ARCH_HAS_PKEYS */
I think I would prefer if VM_PKEY_BIT4 was unusable on x86, or #defined to 0. We don't want folks using a bit that can not be programmed into the hardware.
