System for locking down part of portion of memory and updating page directory with entry corresponding to part of portion of the memory locked down

• US 5,675,762 A
• Filed: 01/06/1995
• Issued: 10/07/1997
• Est. Priority Date: 04/03/1992
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Yee, Susan, Hyde, David Michael, Bodin, William Kress, Wilkinson, James, Lay, Tatchi Placido
• Primary Examiner(s): Meky, Moustafa M.
• Application Number:
  US08/369,330
• Time in Patent Office: 1,005 Days
• Field of Search: 395/406, 395/417, 395/415, 395/412, 395/418, 395/416, 395/413, 395/800, 395/480, 395/823
• US Class Current: 711/206
• CPC Class Codes: G06F 12/1081 for peripheral access to main memory, e.g. direct memory access [DMA]

Abstract

A method and apparatus are disclosed for providing exchange of data between a peripheral device having a paging mechanism and an application operating in a virtual machine which includes a page directory for exclusive use by the paging mechanism of the peripheral device. The virtual machine is running on a data processing system and preferably contains a block of memory which is divided into various sections of memory. The page directory is provided to the paging mechanism of the peripheral device when the application requires the use of the peripheral device. A section of memory is selectively locked down in response to the section of memory being utilized by the application. Additionally, the page directory is updated with an entry which identifies the section of memory that is locked down. Memory may also be locked down in order to permit the peripheral device to access that section of memory. The page directory is selectively updated thereafter by mapping entries into the page directory in order to track memory usage within the block of memory utilized by the virtual machine. The page directory is preferably created at the same time the virtual machine is created. Memory for utilization by the virtual machine is preferably locked down while the virtual machine is in the foreground. When the virtual machine is terminated or moved into the background, the sections of memory that have been locked down are then unlocked or freed for other use.

Claims

1. A method in a data processing system for providing exchange of data between a peripheral device having a paging mechanism and an application operating in a virtual machine, wherein said virtual machine is running on said data processing system and contains a block of memory having a plurality of sections of memory, comprising:

providing a page directory for exclusive use by said paging mechanism of said peripheral device in response to said application requiring usage of said peripheral device;

selectively locking down a section of said block of memory within said data processing system in response to a usage of said section of memory by said application;

updating said page directory with an entry corresponding to said section of said block of memory locked down to allow said peripheral device access to said section of said block of memory, wherein data within said section of said block of memory is unswappable; and

selectively updating therafter said page directory by mapping an entry into said page directory in response to said usage of said section of said memory in order to track memory usage within said block of memory utilized by said virtual machine.

2. The method of claim 1 further comprising the step of creating and locking down said page directory in response to creation of said virtual machine for exclusive use by said paging mechanism of said peripheral device.

3. The method of claim 2 further comprising the step of freeing said section of memory locked down in response to termination of said virtual machine.

4. The method of claim 3 further comprising the step of freeing said section of memory locked down in response to a switch of said virtual machine into background.

5. The method of claim 4 further comprising the step of freeing said section of memory locked down in response to said application no longer requiting access to said peripheral device.

6. The method of claim 5, wherein said page directory contains a page table and a page frame and wherein said step of updating said page directory comprising the step of mapping entries representing memory locations in a linear address form.

7. The method of claim 6, further comprising the step of updating said page directory to reflect accesses made to said block of memory while said virtual machine has been switched into background.

8. A data processing system for providing exchange of data between a peripheral device having a paging mechanism and application operating in a virtual machine, wherein said virtual machine is running on said data processing system and contains a block of memory having a plurality of sections of memory, said apparatus comprising:

means for providing a page directory for exclusive use by said paging mechanism of said peripheral device in response to said application requiring usage of said peripheral device;

means for selectively locking down a section of said block of memory within said data processing system in response to a usage of said section of memory by said application; and

means for updating said page directory with an entry corresponding to said section of said block of memory locked down to allow said peripheral device access to said section of said block of memory, wherein data within said section of said block of memory is unswappable; and

means for selectively updating thereafter said page directory by mapping an entry into said page directory in response to said usage of said section of said memory in order to track memory usage within said block of memory utilized by said virtual machine.

9. The data processing system according to claim 8 further comprising means for creating and locking down said page directory in response to creation of said virtual machine for exclusive use by said paging mechanism of said peripheral device.

10. The data processing system according to claim 9 further comprising means means for freeing said section of memory locked down in response to termination of said virtual machine.

11. The data processing system according to claim 10 further comprising means for freeing said section of memory locked down in response to a switch of said virtual machine into background.

12. The data processing system according to claim 11 further comprising means for freeing said section of memory locked down in response to said application no longer requiring access to said peripheral device.

13. The data processing system according to claim 12, wherein said page directory includes a page table and a page frame and wherein said means for selectively updating said page directory comprising means for mapping entries representing memory locations in a linear address form.

14. The data processing system according to claim 13, further comprising means for updating said page directory to reflect accesses made to said block of memory while said virtual machine has been switched into background.

15. A data processing system for providing exchange of data between a peripheral device and an application, said data processing system comprising:

a system memory;

a peripheral device, wherein said peripheral device access data in said system memory utilizing fixed locations within said system memory;

a page directory, wherein said page directory is for use by said peripheral device;

a virtual machine located within said system memory, wherein said virtual machine utilizes a portion of said system memory;

an application executing within said virtual machine, wherein said application utilizes a part of said portion of said system memory;

locking means, responsive to use of said peripheral device by said application, for locking down said part of said portion of said system memory utilized by said application, wherein said part of said portion of system memory that is locked down is unswappable; and

updating means for updating said page directory with an entry corresponding to said part of said portion of system memory that is locked down by said locking means, wherein said peripheral device utilizes said page directory to access said part of said portion of system memory that is locked down.

16. The data processing system of claim 15 wherein all of said part of said portion of system memory that is locked down is contiguous.

17. The data processing system of claim 15 wherein all of said part of said portion of said system memory that is locked down is noncontiguous.

18. The data processing system of claim 17, wherein said page directory is for use only by said peripheral device.