VIRTUAL MACHINE CONTROL PROGRAM AND VIRTUAL MACHINE SYSTEM

• US 20080307180A1
• Filed: 02/13/2008
• Published: 12/11/2008
• Est. Priority Date: 06/06/2007
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Tsushima, Yuji, Moriki, Toshiomi, HATTORI, Naoya
• Granted Patent: US 8,099,575 B2
• Time in Patent Office: Days
• US Class Current: 711/163
• CPC Class Codes: G06F 2009/45579 I/O management, e.g. providing access to device drivers or storage
• CPC Class Codes: G06F 2009/45587 Isolation or security of virtual machine instances
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects

Abstract

The program attains compatibility of suppression of an overhead accompanying page exception handling in the case of operating a program whose amount of memory use is large on a virtual machine and suppression of the overhead accompanying page exception handling in the case of operating a first OS that has a function of making another OS run on a virtual machine. A VMM creates a shadow PT for prohibiting reading-writing of privileged memory that requires emulation of reading/writing by using a RSV-bit, and registers the shadow PT and the second PT that a second OS operating on the first OS has in an x86 compatible CPU equipped with a page exception detecting function using two PT'"'"'s. When a page exception occurs, the VMM refers to a cause code of the page exception and, when a P field of the cause code is 0, determines immediately that emulation is unnecessary.

Claims

1. A control program of a virtual machine that makes a plurality of OS'"'"'s operate using a computer having a CPU and memory,

wherein the CPU has a memory protection function that is controlled based on a data structure,

wherein the data structure has a first field and a second field that control approval/disapproval of a memory operation in each memory area,

wherein the memory protection function, when the first or second field is set as operation-prohibited, generates a protection exception to an operation of the memory area and generates a cause code indicating a field that becomes an occurrence reason of the protection exception,

wherein the OS controls a first data structure made up of the data structure on the memory,

wherein the memory area that is specified to be operation-prohibited by the first field of the first data structure is wider than the memory area that is specified to be operation-prohibited by the second field of the first data structure,

wherein the control program makes the computer execute a procedure of referring to the first data structure, a procedure of creating the second data structure that is made up of the data structure and whose second field prohibits a memory operation of the memory area that requires emulation of reading/writing, a procedure of making the memory protection function refer to the second data structure, and a procedure of determining necessity of emulation by referring to the cause code at the time of occurrence of the protection exception.

2. The control program of a virtual machine according to claim 1,

wherein the control program makes the computer execute a procedure of setting as operation-prohibited the second field in the second data structure for the memory area used for a control of an I/O device.

3. The control program of a virtual machine according to claim 1,

wherein the control program, when initializing the second data structure, makes the computer execute a procedure of setting the second field in the second data structure as operation-prohibited.

4. The control program of a virtual machine according to claim 1,

wherein the control program, at the time of occurrence of protection exception, when a reason of occurrence of the protection exception indicated by the cause code is the first field, makes the computer execute a procedure of determining that emulation is unnecessary.

5. The control program of a virtual machine according to claim 1,

wherein the control program makes the computer execute a procedure of, at the time of initializing the second data structure, resetting a use flag for showing a use situation of the second field in the first data structure, a procedure of reading a setting of the second field in the first data structure, and when operation prohibition is being set, setting the use flag, a procedure of, at the time of occurrence of the protection exception, reading the cause code, and a procedure of, when the cause code indicates the second field and the use flag is being reset, determining that emulation is required.

6. The control program of a virtual machine according to claim 1,

wherein the CPU is an x86 compatible CPU supporting VT-x, the data structure is a page table, the first field is a Present bit, the second field is a Reserved bit, the cause code is an error code of a page fault, the OS has an event handler of the OS, the control program makes the computer execute a procedure of, at the time of occurrence of a page fault resulting from an operation of the memory area where the present bit is 0, setting page-fault error-code mask and page-fault error-code match that the CPU has so as to cause a branch directly to an event handler of the OS.

7. The control program of a virtual machine according to claim 1,

wherein the OS is a first OS having a function of making a plurality of second OS'"'"'s operate on the OS, the second OS has a third data structure made up of the data structure and a second event handler, the CPU is an x86 compatible CPU, the data structure is the page table, the first field is a Present bit, the second field is a Reserved bit, the cause code is an error code of a page fault, the CPU is a CPU that uses a fourth page table for specifying a condition of the page fault for calling the second event handler and a fifth page table for specifying a condition of the page fault to be reported to the even handler that the control program of the virtual computer has, and

wherein the control program makes the computer execute a procedure of making the CPU refer to the third data structure as the fourth page table, and a procedure of making the CPU refer to the second data structure as the fifth page table.

8. The control program of a virtual machine according to claim 1,

wherein the first field shows whether stored data of a memory area exists on the memory.

9. A virtual machine system having a CPU and memory in which a plurality of OS'"'"'s and a control program for making the plurality of OS'"'"'s operate are installed,

wherein the CPU has a memory protection function controlled based on a data structure,

wherein the data structure includes the first field and the second field that control approval/disapproval of a memory operation in each memory area,

wherein the memory protection function generates a protection exception to an operation of the memory area when the first or second field thereof is set as operation-prohibited, and creates the cause code indicating a field that became a reason of occurrence of the protection exception,

wherein the OS controls the first data structure that is made up of the data structure on the memory,

wherein the first data structure is such that a memory area being set as operation-prohibited by the first field is larger than the memory area being set as operation-prohibited by the second field, and

wherein the control program has:

a function of referring to the first data structure;

a function of creating a second data structure that is made up of the data structure and such that a memory operation of the memory area requiring emulation of reading/writing is prohibited using the second field;

a function of making the memory protection function refer to the second data structure; and

a function of determining the necessity of emulation by referring to the cause code at the time of occurrence of the protection exception.

10. The virtual machine system according to claim 9,

wherein the control program has a function of setting the second field in the second data structure as operation-prohibited for a memory area used for a control of an I/O device.

11. The virtual machine system according to claim 9,

wherein the control program has a function of, when initializing the second data structure, setting the second field in the second data structure as operation-prohibited.

12. The virtual machine system according to claim 9,

wherein the control program has a function of, when a reason of the occurrence of the protection exception indicated by the cause code is the first field at the time of occurrence of the protection exception, determining that emulation is unnecessary.

13. The virtual machine system according to claim 9,

wherein the control program has:

a function of, at the time of initializing the second data structure, resetting a use flag that indicates use situation of the second field in the first data structure;

a function of reading the setting of the second field in the first data structure, and when operation prohibition is set, setting the use flag;

a function of, at the time of occurrence of the protection exception, reading the cause code, and

a function of, when the cause code indicates the second field and the use flag is reset, determining that emulation is required.

14. The virtual machine system according to claim 9,

wherein the CPU is an x86 compatible CPU supporting VT-x, the data structure is a page table, the first field is a Present bit, the second field is a Reserved bit, the cause code is an error code of a page fault, the OS has an event handler of the OS, and the control program has a function of, at the time of occurrence of a page fault resulting from an operation of a memory area where a Present bit is 0, setting page-fault error-code mask, page-fault error-code match, and execution bitmap that the CPU has to cause a branch directly to an event handler of the OS.

15. The virtual machine system according to claim 9,

wherein the OS is the first OS having a function of making a plurality of second OS'"'"'s operate on the OS, the second OS has a third data structure made up of the data structure and the second event handler, the CPU is an x86 compatible CPU, the data structure is a page table, the first field is a Present bit, the second field is a Reserved bit, the cause code is an error code of a page fault, wherein the CPU is a CPU that uses a fourth page table for specifying a condition of the page fault on which the second event handler is called and a fifth page table for specifying a condition of the page fault that is reported to the event handler that the control program of the virtual machine has, and

wherein the control program has a function of making the CPU refer to the third data structure as the fourth page table and a function of making the CPU refer to the second data structure as the fifth page table.

16. The virtual machine system according to claim 9,

wherein the first field indicates whether stored data of the corresponding memory area exists on the memory.

17. A virtual machine system that is realized by program processing using a computer system including a CPU and memory and in which a plurality of OS'"'"'s and a control program for driving the plurality of OS'"'"'s are installed,

wherein each of the plurality of OS'"'"'s is equipped with a first event handler and a first data structure such that the memory is divided into a plurality of memory areas and a memory address and access approval/disapproval are controlled in the each memory area,

wherein the control program is equipped with a second event handler, a first function of executing emulation in response to an instruction issued by each of the plurality of OS'"'"'s, and a second function of creating a second data structure reflecting the first data structure,

wherein each of the first and second data structures is equipped with the first field and that second field that specify access approval/disapproval in the each memory area,

wherein the CPU makes notification to the first event handler when the first field of the second data structure is set as access-prohibited,

wherein the CPU makes notification to the second event handler when the second field of the second data structure is set as access-prohibited, and

wherein the control program executes the emulation when notification is made to the second event handler.

18. The virtual machine system according to claim 17,

wherein the second function is for setting the second field of the second data configuration as access-prohibited for a memory area used for a control of an I/O device.

19. The virtual machine system according to claim 17,

wherein the second function sets the second field of the second data structure as access-prohibited, as an initial state, subsequently, when the plurality of OS'"'"'s issue an access instruction to the memory based on the first data structure, detects this access instruction through the second event handler, and creates the second data structure corresponding to this access instruction.

20. The virtual machine system according to claim 17,

wherein the control program is further equipped with a third function of controlling use/nonuse of the second field of the first data structure, and when the CPU makes notification to the second event handler and provided that there is no use of the second field of the first data structure, the third function executes the emulation.