KVM: S390: protvirt: Introduce instruction data area bounce buffer

KVM: S390: protvirt: Introduce instruction data area bounce buffer

Now that we can't access guest memory anymore, we have a dedicated
satellite block that's a bounce buffer for instruction data.

We re-use the memop interface to copy the instruction data to / from
userspace. This lets us re-use a lot of QEMU code which used that
interface to make logical guest memory accesses which are not possible
anymore in protected mode anyway.

Signed-off-by: Janosch Frank <[email protected]>
Reviewed-by: Thomas Huth <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
[[email protected]: patch merging, splitting, fixing]
Signed-off-by: Christian Borntraeger <[email protected]>