On 3/14/2016 11:57 PM, Jason Gunthorpe wrote: > The other issue is that the fencing mechanism RDMA uses to create > ordering with system memory is not good enough to fence peer-peer > transactions in the general case. It is only possibly good enough if > all the transactions run through the root complex. Are you sure this is a problem? I'm not sure it is clear in the PCIe specs, but I thought that for transactions that are not relaxed-ordered and don't use ID-based ordering, a PCIe switch must prevent reads and writes from passing writes. I assume this is true even when the requestor ID is different because IDO relaxes these constraints specifically for transactions coming from different requestor IDs. Regards, Haggai -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>