vfio/ccw: allow non-zero storage keys

Currently, vfio-ccw copies the ORB from the io_region to the
channel_program struct being built. It then adjusts various
pieces of that ORB to the values needed to be used by the
SSCH issued by vfio-ccw in the host.

This includes setting the subchannel key to the default,
presumably because Linux doesn't do anything with non-zero
storage keys itself. But it seems wrong to convert every I/O
to the default key if the guest itself requested a non-zero
subchannel (access) key.

Any channel program that sets a non-zero key would expect the
same key returned in the SCSW of the IRB, not zero, so best to
allow that to occur unimpeded.
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

drivers/s390/cio/vfio_ccw_cp.c

@@ -836,7 +836,6 @@ union orb *cp_get_orb(struct channel_program *cp, struct subchannel *sch)
 
 	orb->cmd.intparm = (u32)virt_to_phys(sch);
 	orb->cmd.fmt = 1;
-	orb->cmd.key = PAGE_DEFAULT_KEY >> 4;
 
 	if (orb->cmd.lpm == 0)
 		orb->cmd.lpm = sch->lpm;