Revision history   OpenPOWER Library

 10.2.2. Context Save/Restore Pointer Register(CSRP_An) 

 The Context Save/Restore Pointer Register (CSRP_An) contains the effective address of a buffer in main storage for the AFU's context data. The buffer is located in the application's effective address space.

 This register is initialized by the operating system or from the process element. The process element information is used when the PSL scheduled processes area is enabled (PSL_SPAP_An[V] = '1').

 When the AFU is operating in a virtualized programming model, the data returned when reading this register is indeterminate. CAIA-compliant devices should return the corresponding process element data when an interrupt is pending for diagnostic purposes.

 There is one register for each PSL slice. Access to these registers should be privileged. These registers must be accessed using a single 64-bit store operation.

 This facility is optional. System software can detect if this feature is supported by writing x'FFFFFFFFFFFFFFFF' to this register and reading back the contents. If a value of zero is returned, this feature is not supported. Any nonzero value indicates that the feature is supported.

 Note: This register is provided as a place holder for storing the contents of the context save/restore pointer in the process element. Because this register is only required for virtualized programming models and read data is intermediate, implementations might choose to not implement a read/write MMIO register for this value.

Access Type

Read/Write

 Base Address Offset

 (P2_Base | P2(n)) + x'0008'; where n is an AFU number.

Context Save / Restore Effective Address

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

Context Save / Restore Effective Address

Limit

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

Bits

Field Name

Description

 0:51

 Effective Address

 Effective address of the application's context save/restore area.

Note: The lower 12-bits of the 64-bit application context save/restore real address are always '0' (that is, 4 KB aligned). In addition, the EA must be aligned on a limit boundary.

 52:63

 Limit

 Context save/restore area limit.

 The 12-bit limit field is used to define the number of pages minus '1' in the application context save/restore area. The last byte of the area is (CSRP_An[0:39] || CSRP_An[Limit]) || 0xFFF.

  


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