Program Status Word
The PSW (Program Status Word) describes the current configuration for the context. It control whenever DAT is enabled or not, which allows virtual spaces. It also controls several flags such as the Wait state, Problem state, interrupt masking and other essential execution parameters.
While the 390 documentation lists the PSW in Most-Significant-Bit order, the PSW listed here will be in Least-Significant-Bit order for simplicity.
| Bits | Name |
|---|---|
| 0 | Extended addressing mode (z/Arch only) |
| 1-7 | Reserved |
| 8 | Unknown (?) |
| 9 | Enable exception for Exponent Underflow |
| 10 | Enable exception for Decimal Overflow |
| 11 | Enable exception for Fixed Point Overflow |
| 12-13 | Condition code |
| 14-15 | Address space control |
| 16 | Problem state (1=Disables unprivileged instruction execution) |
| 17 | Wait state (Wait for interrupt) |
| 18 | Machine Check Interrupt mask |
| 19 | 1=S390, 0=z/Arch |
| 20-23 | PSW Key for complex memory protection |
| 24 | External Interrupt mask |
| 25 | Input/Output Interrupt mask |
| 26 | Enable DAT |
| 27-29 | Reserved |
| 30 | Enable program event recording |
| 31 | Reserved and must be 0 |
See also
External links
- https://www.kernel.org/doc/html/v5.3/s390/debugging390.html Contains the structure of the PSW (in MSB order)