Branch entry to page services

Branch entry is available for all page services, but macro interfaces are provided only for the PGSER, PGFIXA, and PGFREEA macros. The PGSER macro, which is the IBM-recommended interface to page services, supports branch entry in both cross memory and non-cross memory mode. The PGFIXA and PGFREEA macros also work in cross memory and non-cross memory mode but should be used only under the special circumstances for which they are intended. The page-fix, page-free, page-load, page-release, page-any, and page-out services support both cross memory and non-cross memory mode; the page-out service supports only non-cross memory mode.

To branch-enter page services that do not provide a macro interface for branch entry, the caller must:

Run in supervisor state with PSW key 0.
Hold the local lock of the currently addressable address space.
Set up the registers as described below for cross memory or non-cross memory mode.
Branch to the service.

Note: The pages that are candidates for page services must be addressable in the current address space. All addresses must be 24-bit addresses.