Memory bus attached input/output (‘I/O’) subsystem management in a computing system

1. An apparatus for memory bus attached Input/Output (‘I/O’) subsystem management in a computing system, the computing system including an I/O subsystem communicatively coupled to a memory bus, the apparatus comprising a computer processor, a computer memory operatively coupled to the computer processor, the computer memory having disposed within it computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of:

detecting, by an I/O subsystem device driver, a hibernation request;

responsive to detecting the hibernation request, setting, by the I/O subsystem device driver, a predetermined memory address to a value indicating that the I/O subsystem is not to service system requests;

detecting, by the I/O subsystem device driver, that the I/O subsystem device driver has been restarted; and

setting, by the I/O subsystem device driver, the predetermined memory address to a value indicating that the I/O subsystem can resume servicing system requests.

2. The apparatus of claim 1 wherein setting, by the I/O subsystem device driver, a predetermined memory address to the value indicating that the I/O subsystem is not to service system requests further comprises sending, by the I/O subsystem device driver to the I/O subsystem, a stop signal across the memory bus.

3. The apparatus of claim 1 wherein setting, by the I/O subsystem device driver, the predetermined memory address to the value indicating that the I/O subsystem can resume servicing system requests further comprises sending, by the I/O subsystem device driver to the I/O subsystem, a start signal across the memory bus.

4. The apparatus of claim 1 further comprising computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of:

copying, by the I/O subsystem device driver, data from main memory to the I/O subsystem; and

responsive to setting the predetermined memory address to the value indicating that the I/O subsystem can resume servicing system requests, copying, by the I/O subsystem device driver, contents of the I/O subsystem to main memory.

5. The apparatus of claim 1 wherein the I/O subsystem is dual in-line memory module (‘DIMM’) form factor flash memory.

6. The apparatus of claim 1 further comprising computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of:

retaining, by the I/O subsystem device driver in nonvolatile memory, I/O subsystem requests that were uncompleted when the hibernation request was detected; and

resuming, by the I/O subsystem device driver, the requests that were uncompleted.

7. The apparatus of claim 6 wherein retaining I/O subsystem requests that were uncompleted when the hibernation request was detected includes masking the I/O subsystem requests.

8. A computer program product for memory bus attached Input/Output (‘I/O’) subsystem management in a computing system, the computing system including an I/O subsystem communicatively coupled to a memory bus, the computer program product disposed upon a non-transitory computer readable medium, the computer program product comprising computer program instructions that, when executed, cause a computer to carry out the steps of:

detecting, by an I/O subsystem device driver, a hibernation request;

responsive to detecting the hibernation request, setting, by the I/O subsystem device driver, a predetermined memory address to a value indicating that the I/O subsystem is not to service system requests;

detecting, by the I/O subsystem device driver, that the I/O subsystem device driver has been restarted; and

setting, by the I/O subsystem device driver, the predetermined memory address to a value indicating that the I/O subsystem can resume servicing system requests.

9. The computer program product of claim 8 wherein setting, by the I/O subsystem device driver, a predetermined memory address to the value indicating that the I/O subsystem is not to service system requests further comprises sending, by the I/O subsystem device driver to the I/O subsystem, a stop signal across the memory bus.

10. The computer program product of claim 8 wherein setting, by the I/O subsystem device driver, the predetermined memory address to the value indicating that the I/O subsystem can resume servicing system requests further comprises sending, by the I/O subsystem device driver to the I/O subsystem, a start signal across the memory bus.

11. The computer program product of claim 8 further comprising computer program instructions that, when executed, cause the computer to carry out the steps of:

copying, by the I/O subsystem device driver, data from main memory to the I/O subsystem; and

responsive to setting the predetermined memory address to the value indicating that the I/O subsystem can resume servicing system requests, copying, by the I/O subsystem device driver, contents of the I/O subsystem to main memory.

12. The computer program product of claim 8 wherein the I/O subsystem is dual in-line memory module (‘DIMM’) form factor flash memory.

13. The computer program product of claim 8 further comprising computer program instructions that, when executed, cause the computer to carry out the steps of: retaining, by the I/O subsystem device driver in nonvolatile memory, I/O subsystem requests that were uncompleted when the hibernation request was detected; and

resuming, by the I/O subsystem device driver, the requests that were uncompleted.

14. The computer program product of claim 13 wherein retaining I/O subsystem requests that were uncompleted when the hibernation request was detected includes masking the I/O subsystem requests.