On Wed, Nov 25, 2015 at 12:21 AM, Lan Tianyu [off-list ref] wrote:

quoted

On 2015年11月25日 13:30, Alexander Duyck wrote:

quoted

No, what I am getting at is that you can't go around and modify the
configuration space for every possible device out there.  This
solution won't scale.

PCI config space regs are emulation by Qemu and so We can find the
free PCI config space regs for the faked PCI capability. Its position
can be not permanent.

Yes, but do you really want to edit every driver on every OS that you plan to
support this on.  What about things like direct assignment of regular Ethernet
ports?  What you really need is a solution that will work generically on any
existing piece of hardware out there.

The fundamental assumption of this patch series is to modify the driver in guest to self-emulate or track the device state, so that the migration may be possible.
I don't think we can modify OS, without modifying the drivers, even using the PCIe hotplug mechanism.  
In the meantime, modifying Windows OS is a big challenge given that only Microsoft can do. While, modifying driver is relatively simple and manageable to device vendors, if the device vendor want to support state-clone based migration.

Thx Eddie