On 23/10/17 10:08 AM, David Laight wrote:
It is also worth checking that the hardware actually supports p2p transfers. Writes are more likely to be supported then reads. ISTR that some intel cpus support some p2p writes, but there could easily be errata against them.
Ludwig mentioned a PCIe switch. The few switches I'm aware of support P2P transfers. So if everything is setup correctly, the TLPs shouldn't even touch the CPU.
But, yes, generally it's a good idea to start with writes and see if they work first.
Logan
