[PATCH v2 01/10] PCI/P2PDMA: Support peer to peer memory

[Stephen Bates]

> I'm pretty sure the spec disallows routing-to-self so doing a P2P 
> transaction in that sense isn't going to work unless the device 
> specifically supports it and intercepts the traffic before it gets to 
> the port.

This is correct. Unless the device intercepts the TLP before it hits the root-port then this would be considered a "route to self" violation and an error event would occur. The same holds for the downstream port on a PCI switch (unless route-to-self violations are disabled which violates the spec but which I have seen done in certain applications).
    
Stephen