On Fri, Mar 16, 2018 at 9:33 PM, Ram Pai <linuxram@xxxxxxxxxx> wrote: > Applications need the ability to associate an address-range with some > key and latter revert to its initial default key. Pkey-0 comes close to > providing this function but falls short, because the current > implementation disallows applications to explicitly associate pkey-0 to > the address range. > > Clarify the semantics of pkey-0 and provide the corresponding > implementation. > > Pkey-0 is special with the following semantics. > (a) it is implicitly allocated and can never be freed. It always exists. > (b) it is the default key assigned to any address-range. > (c) it can be explicitly associated with any address-range. > > Tested on powerpc only. Could not test on x86. Ram, I was wondering if we should check the AMOR values on the ppc side to make sure that pkey0 is indeed available for use as default. I am still of the opinion that we should consider non-0 default pkey in the long run. I'm OK with the patches for now, but really 0 is not special except for it being the default bit values present in the PTE. The patches themselves look OK to me Balbir Singh.
