MANAGING SAFE REMOVAL OF A PASSTHROUGH DEVICE IN A VIRTUALIZATION SYSTEM

• US 20140068607A1
• Filed: 09/05/2012
• Published: 03/06/2014
• Est. Priority Date: 09/05/2012
• Status: Active Grant

• Current Assignee: Red Hat Israel Ltd. (International Business Machines Corporation)
• Original Assignee: Red Hat Israel Ltd. (International Business Machines Corporation)
• Inventors: Tsirkin, Michael, Williamson, Alex Lee
• Granted Patent: US 9,043,789 B2
• Time in Patent Office: Days
• US Class Current: 718/1
• 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

Abstract

Methods and systems for managing a removal of a passthrough device from a guest managed by a hypervisor in virtualized computing environment. A hypervisor receives a request from the guest for access to a passthrough device. The hypervisor sets, in a memory, a last accessed state associated with a virtual machine executing the guest. The hypervisor forwards the request to the passthrough device and configures the host CPU to send a subsequent access request directly to the passthrough device. In response to a virtual machine reset, the hypervisor clears the last accessed state and instructs the host CPU to send a post-reset access request to the hypervisor.

Claims

1. A method, comprising:

receiving, by a hypervisor, a request from a guest for access to a passthrough device;

setting in a memory, by the hypervisor, a last accessed state associated with a virtual machine executing the guest;

forwarding, by the hypervisor, the request to the passthrough device;

configuring, by the hypervisor, a host central processing unit (CPU) to send a subsequent access request directly to the passthrough device; and

in response to a virtual machine reset, clearing the last accessed state and instructing the host CPU to send a post-reset access request to the hypervisor.

2. The method of claim 1, further comprising:

receiving, by the hypervisor, a request to remove the passthrough device from the guest; and

removing, by the hypervisor, the passthrough device associated with the guest without receiving an acknowledgment from the guest when the last accessed state is clear.

3. The method of claim 2, wherein the request to remove the passthrough device is received from a management interface of the hypervisor.

4. The method of claim 2, further comprising removing, by the hypervisor, the device associated with the guest without receiving an acknowledgement from the guest when the virtual machine is reset.

5. The method of claim 1, further comprising notifying the guest of the request to remove the passthrough device when the last accessed state is set.

6. The method of claim 1, further comprising:

receiving, by the hypervisor, a first post-reset request from the guest for access to the passthrough device;

setting in the memory, by the hypervisor, the last accessed state associated with the virtual machine executing the guest;

forwarding, by the hypervisor, the first post-reset request to the passthrough device;

and

configuring, by the hypervisor, the host CPU to send a subsequent post-reset access request directly to the passthrough device.

7. The method of claim 1, wherein the request for access comprises a configuration access request and the passthrough device comprises a Peripheral Component Interconnect (PCI) device.

8. A non-transitory computer readable storage medium including instructions that, when executed by a processing device, cause the processing device to perform operations comprising:

receiving, by a hypervisor, a request from a guest for access to a passthrough device;

setting in a memory, by the hypervisor, a last accessed state associated with a virtual machine executing the guest;

forwarding, by the hypervisor, the request to the passthrough device;

configuring, by the hypervisor, a host CPU to send a subsequent access request directly to the passthrough device; and

in response to a virtual machine reset, clearing the last accessed state and instructing the host CPU to send a post-reset access request to the hypervisor.

9. The non-transitory computer readable storage medium of claim 8, further comprising:

receiving, by the hypervisor, a request to remove the passthrough device from the guest; and

removing, by the hypervisor, the passthrough device associated with the guest without receiving an acknowledgment from the guest when the last accessed state is clear.

10. The non-transitory computer readable storage medium of claim 9, wherein the request to remove the passthrough device is received from a management interface of the hypervisor.

11. The non-transitory computer readable storage medium of claim 8, further comprising notifying the guest of the request to remove the passthrough device when the last accessed state is set.

12. The non-transitory computer readable storage medium of claim 8, further comprising:

receiving, by the hypervisor, a first post-reset request from the guest for access to the passthrough device;

setting in the memory, by the hypervisor, the last accessed state associated with the virtual machine executing the guest;

forwarding, by the hypervisor, the first post-reset request to the passthrough device;

and

configuring, by the hypervisor, the host CPU to send a subsequent post-reset access request directly to the passthrough device.

13. The non-transitory computer readable storage medium of claim 8, wherein the request for access comprises a configuration access request and the passthrough device comprises a Peripheral Component Interconnect (PCI) device.

14. A computer system comprising:

a memory;

a processing device, coupled to the memory; and

a hypervisor hosted by the computer system, having access to the memory and use of the processing device, the hypervisor configured to;

receive a request from a guest for access to a passthrough device,

set in the memory a last accessed state associated with a virtual machine executing the guest,

forward the request to the passthrough device,

configure a host central processing unit (CPU) to send a subsequent access request directly to the passthrough device, and

in response to a virtual machine reset, clear the last accessed state and instructing the host CPU to send a post-reset access request to the hypervisor.

15. The computer system of claim 14, wherein the hypervisor is configured to:

receive a request to remove the passthrough device from the guest, and

remove the passthrough device associated with the guest without receiving an acknowledgment from the guest when the last accessed state is clear.

16. The computer system of claim 15, wherein the request to remove the passthrough device is received from a management interface of the hypervisor.

17. The computer system of claim 14, wherein the hypervisor is configured to notify the guest of the request to remove the passthrough device when the last accessed state is set.

18. The computer system of claim 14, wherein the hypervisor is configured to:

receive a first post-reset request from the guest for access to the passthrough device,

set in the memory the last accessed state associated with the virtual machine executing the guest,

forward the first post-reset request to the passthrough device, and

configure the host CPU to send a subsequent post-reset access request directly to the passthrough device.

19. The computer system of claim 14, wherein the request for access comprises a configuration access request and the passthrough device comprises a Peripheral Component Interconnect (PCI) device.

20. A computing system comprising

a memory;

and

a hardware bus coupled to the memory, the hardware bus comprising hardware device unplug logic configured to;

maintain in the memory a bit representing a last accessed state associated with an operating system of the computing system, wherein the last accessed state is cleared by the hardware bus when the computing system is reset, and wherein the last accessed state is set by the hardware bus when the hardware bus detects a request from the operating system to access a device,

receive a request to remove the device, and

remove the device without receiving an acknowledgment from a firmware of the device when the last accessed state is clear.

21. The computing system of claim 20, wherein the hardware device unplug logic is configured to clear the last accessed state when the computing system is reset.