On 08/18/11 20:04, Daniel P. Berrange wrote:
> I've been experimenting with multiple USB2 buses, and device physical port
> addressing. It seems if you have 2 devices of the same type on the same
> port, but in different buses, you get a bogus VMState assertion failure

>      qemu-system-x86_64: savevm.c:1260: vmstate_register_with_alias_id: Assertion `!se->compat || se->instance_id == 0' failed.
>      Aborted

> AFAICT, the problem is that the 'se->idstr' field in the SaveStateEntry
> struct is not getting a unique enough value.
>
> Both the USB devices get idstr named   "1/usb-ccid", which IIUC is a
> combination of the device type and the port number.

Indeed.

> IMHO, it needs to have the USB bus name in there too eg. in this
> example it should have been
>
>      ehci0.0/1/usb-ccid
>      ehci1.0/1/usb-ccid

I assumed the savevm code walks up the device path and creates a unique 
name by prefixing the string with the parents pci address, but it 
doesn't :-(

We can do that outself though, see attached patch.
That gives us IDs like this:

   0000:00:01.2/uhci              (hcd, unchanged)
   0000:00:01.2/1/usb-ptr         (usb devs, now with hcd pci addr)

Juan?  Does that look sane?

cheers,
   Gerd