On Fri, Mar 9, 2018 at 7:12 PM, Ram Pai <linuxram@xxxxxxxxxx> wrote: > Once an address range is associated with an allocated pkey, it cannot be > reverted back to key-0. There is no valid reason for the above behavior. On > the contrary applications need the ability to do so. > > The patch relaxes the restriction. I looked at the code and my observation was going to be that we need to change mm_pkey_is_allocated. I still fail to understand what happens if pkey 0 is reserved? What is the default key is it the first available key? Assuming 0 is the default key may work and seems to work, but I am sure its mostly by accident. It would be nice, if we could have a notion of the default key. I don't like the special meaning given to key 0 here. Remember on powerpc if 0 is reserved and UAMOR/AMOR does not allow modification because it's reserved, setting 0 will still fail Balbir
