accurate>> 0xd5200000-0xd52fffff 64bit pref] >> [ 2107.015060] pci 0000:09:00.0: Max Payload Size 128, but upstream >> 0000:05:07.0 set to 256; if necessary, use "pci=pcie_bus_safe" and report a >> bug >> [ 2107.015079] pci 0000:09:00.0: no hotplug settings from platform >> >> The commit message that added the warning indicates it may be a BIOS >> issue that incorrectly configures this, but BIOS isn't involved with >> setting the MPS on a device hot add, am I right? Or is that wrong? > > The BIOS is not involved in setting MPS on a device hot-add. > >> This is a Dell R620 server, if that matters, though we see this on other >> platforms as well. >> >> Using pci=pcie_bus_perf works around the issue, but that seems a bit >> odd to suggest to users. Is setting MPS on hot-add something the PCI >> driver layer ought to be doing, or should I be looking into the platform >> BIOS instead? > > The PCI core should be doing something intelligent here. If we can't > configure MPS safely, we should prevent the device from being enabled. > But this is stuff the PCI core doesn't implement yet. Hi Bjorn, We had a long discussion about fix this issue. Link: http://marc.info/?l=linux-pci&m=137714192204947&w=2 Now more BIOS configure device mps larger than 128B, So I think we should consider to fix it before we have a perfect solution about mps setting. > > It's hard to reconfigure MPS after boot because it affects other > devices in the system, and I don't think we can always change the > settings of other devices while they're active. Yes, what we can only change is the device not active after hotplug. > > I'm not sure that warning is correct. It seems like it should suggest > pcie_bus_peer2peer, which is documented as guaranteeing that hot-added > devices will work. But this is always confusing to me, and I could be > wrong about this. I think warning is proper, pcie_bus_safe is designed to fix the hotlplug issue. pcie_bus_peer2perr guarantee that hotplug device work fine, because all mps setting 128B. Maybe we should change document a little, make it more clear. > > Bjorn > > -- Thanks! Yijing -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
