On 2025-04-08 09:28, Lukas Wunner wrote: > On Tue, Apr 08, 2025 at 06:14:55PM +0300, Damir Chanyshev wrote: >> On Tue, Apr 8, 2025 at 6:06???PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: >>> The pci_p2pdma_whitelist[] is only updated when somebody tests a >>> platform and determines that its RC can route peer-to-peer >>> transactions between separate Root Ports. This routing is not >>> required by the PCIe spec, so we can't assume that all platforms >>> support it. >> >> For the testing, is simple rdma ping-pong sufficient? Or a more >> specific testing tool? >> Unfortunately I don't have a fancy pcie hardware analyzer. > > You should test that performance is satisfactory for you needs. I couldn't have said it better myself. If you have any application running on a machine that uses P2P then that is sufficient testing in and of itself to add the machine to the list. My expectation is that any modern Intel root complex should work, but we don't have a concise rule that guarantees this so we are stuck in the unfortunate situation to add each family as they are tested by someone who cares about it. AMD confirmed for us that all modern devices will support P2P and provided a concise rule that works for all current and future devices. My limited experience with ARM devices suggest many root complexes do not support P2P, so they will likely always have to be added on a case by case basis. Logan
