savevm-external (the return: the movie part II - the end)

[branylagaffe]

I want QEMU to release the lock of the qcow2 file after generating the snapshot,
So that another QEMU instance can start from this snapshot using this qcow2 file.

The following specifications are defined with two QEMU instances:

• Instance 1: the functional warming simulator, fw
• Instance 2: the timing simulator, t

Specification:
When fw is asked to generation a checkpoint, it should:

1. Create a new qcow2 file using the current qcow2 file as its base
2. "Use" the qcow2 file created in step 1 as the current simulation disk
3. Release the lock of the qcow2 file mentioned in step 1

Yuanlong told me that QEMU has implemented similar code for this functionality. We may combine them.

Tasks:

• Ask Yuanlong for the existing mechanism and note down (by @xusine )

[branylagaffe]

@xusine Please fill in the template, to specify the feature of the savevm-external (once for all)