[+cc Logan, Stephen, Jonathan, Eric, Alex] On Sat, Dec 22, 2018 at 12:50:19PM +0800, yu wrote: > Hi all, > > We have a PCIE card which has a PEX8732 switch on-board, and there > are two endpoint SOCs like graphic decoder behind the switch, and by > default the ACS is enabled in 8732. > > We use the p2p DMA to transfer data between these two endpoint SOCs, > and if the host server is not enable ACS in BIOS, the p2p works well, > but when ACS is enabled in BIOS, the p2p is always failed. With the > help of a protocol analyzer, we can see that the TLP is redirected to > RC, and RC just discard it. > > I tried to find how to make RC forward redirected TLP to its original > target, but nothing found, it seems this is highly related to the RC > vendors. > > In the PCIE 4.0 spec, the section of the RC behavior of the p2p > request redirect said that ''implementation-specific logic within the > RC that determines whether the request is directed towards its > original target, or blocked as an ACS Violation error. the algorithms > and specific controls for making this determination are not > architected by this spec''. > > > So is there some spec or document to describe how to set the RC? Any > suggestion is appreciated. Not that I'm aware of, but the folks I cc'd would know a lot more about this area. Bjorn
