Configuration space virtualization

• US 8,117,346 B2
• Filed: 10/03/2008
• Issued: 02/14/2012
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Oshins, Jacob, Allsop, Brandon, Thornton, Andrew John
• Primary Examiner(s): Tseng, Cheng-Yuan
• Application Number:
  US12/245,543
• Publication Number:
  US 20100088431A1
• Time in Patent Office: 1,229 Days
• Field of Search: None
• US Class Current: 710/2
• CPC Class Codes: G06F 2009/45579 I/O management, e.g. providing access to device drivers or storage
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects
• CPC Class Codes: G06F 9/468 Specific access rights for resources, e.g. using capability register
• CPC Class Codes: G06F 9/5077 Logical partitioning of resources; Management or configuration of virtualized resources specific details on emulation or internal functioning of virtual machines G06F9/455

Abstract

Various aspects are disclosed herein for bounding the behavior of a non-privileged virtual machine that interacts with a device by creating a description of the device which indicates to a privileged authority (1) which operations on the device may have system-wide effects and (2) which operations have effects local to the device. The privileged authority may then permit or deny these actions. The privileged authority may also translate these actions into other actions with benign consequences.

Claims

1. A computer implemented method for managing communications between a virtual machine and an I/O device, comprising:

receiving a description of the I/O device, the description indicative of which actions may be performed on the I/O device by a non-privileged virtual machine;

based on said description, constructing a representation of configuration space for the I/O device, the representation being usable by the computer to restrict operations that can be performed on memory locations within said configuration space;

constructing a representation of memory mapped I/O space based on said description, the representation comprising;

a first level of memory mapped I/O space constructed by determining pages of the memory mapped I/O space to be mapped into the virtual machine; and

a second level of memory mapped IO space constructed by determining bits of the memory mapped I/O space to be mapped into the virtual machine as static values; and

in accordance with said representation of configuration space and said representation of memory mapped I/O space, making a determination that a non-privileged virtual machine is attempting an operation on a location within the representation of configuration space or on a location within the representation of memory mapped I/O space;

intercepting the operation; and

permitting, denying, or translating the operation in accordance with the description indicative of actions that may be performed on the I/O device by the non-privileged virtual machine.

2. The method according to claim 1, wherein said constructing a representation of configuration space further comprises associating each bit within said representation of configuration space with at least one read and write operation.

3. The method according to claim 1, wherein for any memory excluded from said representation of configuration space or for any memory excluded from said representation of memory mapped I/O space, populating said any memory with data representative of said I/O device.

4. The method according to claim 2, wherein said read and write operations comprise:

read-only, always zero on read, always one on read, read-write, write of one clears/write of zero leaves alone, write of one sets/write of zero leaves alone, write of zero clears/write of one leaves alone, write of zero sets/write of one leaves alone, clear to zero after first read, and set to one after first read.

5. The method according to claim 3, further comprising:

defining bits within pages for the excluded memory,

wherein said permitting, denying or translating comprises using pages with the defined bits.

6. The method according to claim 1, wherein said description is received in a file provided by a vendor of said I/O device, and wherein said constructing a representation of configuration space and said constructing a representation of memory mapped I/O space further comprises constructing the representation in accordance with said description.

7. The method according to claim 6, wherein said file is digitally signed by said vendor.

8. The method according to claim 1, wherein said managing is performed by a virtualizing layer.

9. The method according to claim 6, further comprising:

constructing a representation of I/O space;

populating said representation of I/O space based on said received information; and

controlling access to said I/O device in accordance with said representation of I/O space.

10. The method according to claim 6, further comprising populating both said representation of configuration space and said representation of memory mapped I/O space based on the received description.

11. The method according to claim 1, further comprising excluding I/O space from said virtual machine.

12. A system for managing communications between a virtual machine and a device, comprising:

at least one processor; and

at least one memory communicatively coupled to said at least one processor, the memory having stored therein computer-executable instructions that, when executed on the processor, cause the processor to perform operations comprising;

receiving a description of the device, the description comprising information regarding which operations on the device have system-wide effects and which have effects that are local to the device;

based on said description, creating a representation of configuration space for the device, the system being configured to use the representation to restrict operations that can be performed on memory locations within said configuration space;

constructing a representation of memory mapped I/O space based on said description, the representation comprising;

a first level of memory mapped I/O space constructed by determining pages of the memory mapped I/O space to be mapped into the virtual machine; and

a second level of memory mapped I/O space constructed by determining bits of the memory mapped I/O space to be mapped into the virtual machine as static values;

in accordance with said representation of configuration space and said representation of memory mapped I/O space, making a determination that a non-privileged virtual machine is attempting an operation on a location within the representation of configuration space or on a location within the representation of memory mapped I/O space;

intercepting the operation; and

permitting, denying, or translating the operation in accordance with the description.

13. The system of claim 12 wherein each bit within said representation of configuration space comprises at least one of the following properties:

read-only, always zero on read, always one on read, read-write, write of one clears/write of zero leaves alone, write of one sets/write of zero leaves alone, write of zero clears/write of one leaves alone, write of zero sets/write of one leaves alone, clear to zero after first read, or set to one after first read.

14. The system according to claim 12, wherein the description is received via an installation file is a digitally signed INF.

15. A computer readable storage medium storing thereon computer executable instructions for controlling access to a device communicatively coupled to a physical machine that hosts virtual machines, comprising instructions for:

receiving an installation file for the device, wherein the installation file comprises information regarding which operations on the device have system-wide effects and which have effects that are local to the device;

based on said description, constructing at least one map of attributes for the device'"'"'s configuration space, memory mapped I/O space and I/O space, the at least one map comprising a representation of memory mapped I/O space, the representation comprising;

a first level of memory mapped I/O space constructed by determining pages of the memory mapped I/O space to be mapped into the virtual machine; and

a second level of memory mapped IO space constructed by determining bits of the memory mapped I/O space to be mapped into the virtual machine as static values;

the at least one map being usable by a virtualization system to restrict operations that can be performed on memory locations within said configuration space, wherein each page or each bit associated with the at least one map is mapped into said virtual machine and wherein a static page of bits can be provided to a virtual machine as the state of the device;

populating the at least one map based on said received installation file;

using the at least one map to manage access the device by;

making a determination that a non-privileged virtual machine is attempting an operation on a location within the representation of configuration space or on a location within the representation of memory mapped I/O space;

intercepting the operation; and

permitting, denying, or translating the operation in accordance with the description.

16. The computer readable storage medium of claim 15 wherein each bit within said map or page associated with the at least one map contains one of the following attributes:

read-only, always zero on read, always one on read, read-write, write of one clears/write of zero leaves alone, write of one sets/write of zero leaves alone, write of zero clears/write of one leaves alone, write of zero sets/write of one leaves alone, clear to zero after first read, or set to one after first read.

17. The computer readable storage medium of claim 15 wherein for any memory excluded from said representation of configuration space or for any memory excluded from said representation of memory mapped I/O space, populating said any memory with predetermined data.

18. The computer readable storage medium of claim 17 wherein said predetermined data corresponds to a predetermined device.

19. The computer readable storage medium of claim 17, further comprising instructions for:

defining bits within pages for the excluded memory,

wherein said permitting, denying or translating comprises using pages with the defined bits.

20. The computer readable storage medium of claim 15, wherein said installation file is an INF provided by a vendor of said device and digitally signed.