| From: Raj, Ashok <ashok.raj@xxxxxxxxx> | Sent: Thursday, August 3, 2017 1:31 AM | | I don't understand this completely.. So your driver would know not to send | RO TLP's to root complex. But you want to send RO to the NVMe device? This | is the peer-2-peer case correct? Yes, this is the "heavy hammer" issue which you alluded to later. There are applications where a device will want to send TLPs to a Root Complex without Relaxed Ordering set, but will want to use it when sending TLPs to a Peer device (say, an NVMe storage device). The current approach doesn't make that easy ... and in fact, I still don't kow how to code a solution for this with the proposed APIs. This means that we may be trading off one performance problem for another and that Relaxed Ordering may be doomed for use under Linux for the foreseeable future. As I've noted a number of times, it would be great if the Intel Hardware Engineers who attempted to implement the Relaxed Ordering semantics in the current generation of Root Complexes had left the ability to turn off the logic which is obviously not working. If there was a way to disable the logic via an undocumented register, then we could have the Linux PCI Quirk do that. Since Relaxed Ordering is just a hint, it's completely legitimate to completely ignore it. Casey
