User space needs a mechanism to perform key checked accesses when
emulating instructions.

The key can be passed as an additional argument.
Having an additional argument is flexible, as user space can
pass the guest PSW's key, in order to make an access the same way the
CPU would, or pass another key if necessary.
Signed-off-by: NJanis Schoetterl-Glausch <scgl@linux.ibm.com>
Reviewed-by: NClaudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: NChristian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: NJanosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20220211182215.2730017-6-scgl@linux.ibm.comSigned-off-by: NChristian Borntraeger <borntraeger@linux.ibm.com>