Method and data processing system for emulating virtual memory working spaces

• US 6,480,845 B1
• Filed: 06/14/2000
• Issued: 11/12/2002
• Est. Priority Date: 06/14/2000
• Status: Expired due to Term

• Current Assignee: Bull HN Information Systems Incorporated (Atos SE)
• Original Assignee: Bull HN Information Systems Incorporated (Atos SE)
• Inventors: Bohult, Stefan R., Egolf, David A., Noyes, Bruce A., Farmer, Chad
• Primary Examiner(s): Mizrahi, Diane D.
• Application Number:
  US09/594,350
• Time in Patent Office: 881 Days
• Field of Search: 707/4, 707/6, 707/7, 707/200, 707/205, 707/206, 703/26, 711/206
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0284 Multiple user address space allocation, e.g. using different base addresses interprocessor communication G06F15/163
• CPC Class Codes: G06F 12/1036 for multiple virtual address spaces, e.g. segmentation G06F12/1045 takes precedence
• CPC Class Codes: G06F 12/109 for multiple virtual address spaces, e.g. segmentation G06F12/1036 takes precedence
• CPC Class Codes: G06F 9/45537 Provision of facilities of other operating environments, e.g. WINE I/O emulation G06F13/105
• CPC Class Codes: Y10S 707/99936 Pattern matching access

Abstract

In an emulation of a multiprocessor Target computer system on a Host computer system, Host virtual memory addresses are mapped and utilized as Target virtual memory addresses. Target virtual memory control tables are setup accordingly. Virtual-to-real address translation of a Target system effective address to a Host system virtual addresses is performed by identifying a working space for the effective address, determining a working space base address for that working space, and then performing a linear translation multiplying the effective address by a constant and adding it to the working space base address to generate the host system virtual address.

Claims

1. A method of performing emulator virtual-to-real address translation translating a target system virtual address to a host memory virtual address during emulation of a target system instruction,

wherein said method comprises:

A) identifying a selected working space from a plurality of working spaces;

B) determining a working space base address for the selected working space; and

C) performing a linear translation from the target system virtual address to the host memory virtual address by;

1) multiplying the target system virtual address by a first constant for a product, and

2) adding the product to the working space base address to compute the host memory virtual address.

2. The method in claim 1 wherein:

the first constant is eight (8).

3. The method in claim 1 wherein:

the target system virtual address is an address of the target system instruction; and

the selected working space is a working space containing the target system instruction.

4. The method in claim 1 wherein:

the target system virtual address is an address of target system data being accessed by the target system instruction; and

the selected working space is selected in step (A) based on information in register selected by a field in the target system instruction.

5. The method in claim 1 wherein:

step (A) comprises;

comparing the target system virtual address against a first of a plurality of working space limits, and

selecting a working space corresponding to the first of the plurality of working space limits if the target system virtual address is within the first of the plurality of working space limits.

6. The method in claim 1 wherein:

the target system virtual address is an address of target system data being accessed by the target system instruction; and

the selected working space is selected in step (A) based on information in a field in an operand referenced by the target system instruction.

7. The method in claim 1 wherein:

the target system virtual address is an address of target system data being accessed by the target system instruction; and

the selected working space is selected in step (A) based on an opcode in the target system instruction.

8. The method in claim 1 wherein:

each of the plurality of working spaces has a corresponding entry in a working space base address table; and

step (B) comprises;

1) identifying the corresponding entry for the selected working space in the working space base address table utilizing a base address table index associated with the selected working space, and

2) utilizing the corresponding entry in the working space base address table identified in substep (1) as the working space base address.

9. The method in claim 8 wherein:

each of the plurality of working spaces has a corresponding entry in a working space limit table; and

the method further comprises;

D) determining whether the target system virtual address is within the selected working space by;

1) identifying the corresponding entry for the selected working space in the working space limit table utilizing a limit table index associated with the selected working space,

2) utilizing the corresponding entry in the working space limit table identified in substep (1) as a working space limit address, and

3) comparing the target system virtual address against the working space limit address to determine whether the target system virtual address is within the selected working space.

10. The method in claim 8 wherein:

each of the plurality of working spaces has a corresponding entry in a working space limit table; and

the method further comprises;

D) determining whether the target system virtual address is within the selected working space by;

1) identifying the corresponding entry for the selected working space in the working space limit table utilizing a limit table index associated with the selected working space,

2) utilizing the corresponding entry in the working space limit table identified in substep (1) as a working space limit address, and

3) comparing the host memory virtual address against the working space limit address to determine whether the target system virtual address is within the selected working space.

11. A method of emulating a target computer system on a host computer system having a host working space,

wherein said method comprises:

A) allocating a first contiguous section of the host working space for a first target working space;

B) inserting a first pointer to the first contiguous section of the host working space into a first entry in a working space base address table;

C) performing emulator virtual to real address translation for a first target virtual address in the first target working space by performing a linear translation from the first target virtual address to a first host memory address by;

1) multiplying the first target virtual address by a first constant for a first product, and

2) adding the first product to the first pointer to compute the host memory address; and

D) deallocating the first contiguous section of the host working space.

12. The method in claim 11 which further comprises:

E) allocating a second contiguous section of the host working space for a second target working space;

F) inserting a pointer to the second contiguous section of the host working space into a second entry in the working space base address table;

G) performing emulator virtual to real address translation for a second target virtual address in the second target working space by performing a linear translation from the second target virtual address to a second host memory address by;

1) multiplying the second target virtual address by the first constant for a second product, and

2) adding the second product to the second pointer to compute the second host memory address; and

H) deallocating the second contiguous section of the host working space.

13. The method in claim 12 wherein:

a third contiguous section of the host working space is managed as host working space buffer pool;

the allocating in step (A) allocates the first contiguous section of the host working space from the host working space buffer pool; and

the allocating in step (E) allocates the second contiguous section of the host working space from the host working space buffer pool.

14. The method in claim 12 wherein:

the allocating in step (A) invokes a first host system function to allocate the first contiguous section of the host working space; and

the deallocating in step (D) invokes a second host system function to deallocate the first contiguous section of the host working space.

15. The method in claim 11 wherein:

step (C) further comprises;

3) loading the first pointer from the first entry in the working space base address table before the first pointer is used in substep (2).

16. The method in claim 11 wherein:

a third contiguous section of the host working space is managed as host working space buffer pool;

the allocating in step (A) allocates the first contiguous section of the host working space from the host working space buffer pool; and

the deallocating in step (D) deallocates the first contiguous section of the host working space back into the host working space buffer pool.

17. The method in claim 11 wherein:

the allocating in step (A) is performed when a first process is initially created; and

the deallocating in step (D) is performed when the first process terminates.

18. The method in claim 11 wherein:

the allocating in step (A) is performed when a target system initializes.

19. The method in claim 11 wherein:

the allocating in step (A) is performed dynamically after a first process is initially created; and

the deallocating in step (D) is performed dynamically before the first process terminates.

20. A data processing system containing emulation software for emulating a target computer system on a host computer system having a host working space, wherein:

the data processing system comprises a Computer Software Storage Medium, and

said emulation software comprises;

A) a set of computer instructions stored in the Computer Software Storage Medium for allocating a first contiguous section of the host working space for a first target working space;

B) a set of computer instructions stored in the Computer Software Storage Medium for inserting a first pointer to the first contiguous section of the host working space into a first entry in a working space base address table;

C) a set of computer instructions stored in the Computer Software Storage Medium for performing emulator virtual to real address translation for a first target virtual address in the first target working space by performing a linear translation from the first target virtual address to a first host memory address by;

1) multiplying the first target virtual address by a first constant for a first product, and

2) adding the first product to the first pointer to compute the host memory address; and

D) a set of computer instructions stored in the Computer Software Storage Medium for deallocating the first contiguous section of the host working space.

21. A Non-Volatile Storage Medium containing Emulation software emulation software for emulating a target computer system on a host computer system having a host working space, wherein:

said emulation software comprises;

A) a set of computer instructions for allocating a first contiguous section of the host working space for a first target working space;

B) a set of computer instructions for inserting a first pointer to the first contiguous section of the host working space into a first entry in a working space base address table;

C) a set of computer instructions for performing emulator virtual to real address translation for a first target virtual address in the first target working space by performing a linear translation from the first target virtual address to a first host memory address by;

1) multiplying the first target virtual address by a first constant for a first product, and

2) adding the first product to the first pointer to compute the host memory address; and

D) a set of computer instructions for deallocating the first contiguous section of the host working space.

22. A data processing system containing emulation software that performs emulator virtual-to-real address translation translating a target system virtual address to a host memory virtual address during emulation of a target system instruction, wherein:

the data processing system comprises a Computer Software Storage Medium, and

said emulation software comprises;

A) a set of computer instructions stored in the Computer Software Storage Medium for identifying a selected working space from a plurality of working spaces;

B) a set of computer instructions stored in the Computer Software Storage Medium for determining a working space base address for the selected working space; and

C) a set of computer instructions stored in the Computer Software Storage Medium for performing a linear translation from the target system virtual address to the host memory virtual address by;

1) multiplying the target system virtual address by a first constant for a product, and

2) adding the product to the working space base address to compute the host memory virtual address.

23. A Non-Volatile Storage Medium containing Emulation software that performs emulator virtual-to-real address translation translating a target system virtual address to a host memory virtual address during emulation of a target system instruction, for use in a data processing system for emulating a target computer system on a host computer system, wherein:

said emulation software comprises;

A) a set of computer instructions for identifying a selected working space from a plurality of working spaces;

B) a set of computer instructions for determining a working space base address for the selected working space; and

C) a set of computer instructions for performing a linear translation from the target system virtual address to the host memory virtual address by;

1) multiplying the target system virtual address by a first constant for a product, and

2) adding the product to the working space base address to compute the host memory virtual address.