On Thu, Sep 20, 2012 at 6:26 AM, Yijing Wang <wangyijing@xxxxxxxxxx> wrote: > On 2012/9/20 9:47, Yijing Wang wrote: >>>> We compared the two situations after BIOS initialization, and found Max Payload Size in DEVCTRL is 256B >>>> if FC card had been installed, if the slot is empty, Max Payload Size is 128B. We force it to be 128B when >>>> FC card installed when system boot up. Finally pci hotplug becomes ok. So I suspect maybe our PCIe hardware >>>> has problem supporting 256B. >>> >>> Ah, this sounds like something I've been worried about for a while, >>> i.e., do we handle MPS correctly when we hot-add devices? >>> >>> Yijing, I'm not quite clear on what you're observing. I guess you're >>> saying that if an FC card is installed at boot, the BIOS sets MPS to >>> 256, and that if no FC card is installed, the BIOS sets MPS to 128? >> >> Yes. >> >>> You haven't mentioned any Linux boot options, so I assume you haven't >>> tried any. Does "pci=pcie_bus_safe" make any difference? >> >> Yes, I don't add any Linux boot options before. I will try this boot option >> "pci=pcie_bus_safe". >> >>> Jon, here's a pointer to the beginning of the thread: >>> http://marc.info/?l=linux-pci&m=134770460302298&w=2 (full dmesg log at >>> http://marc.info/?l=linux-scsi&m=134788365823217&w=2). I'm not sure >>> we have enough in the dmesg log to diagnose an issue like this. I >>> wonder if it would be useful to log the current setting, so we could >>> notice BIOS default differences like this one. >>> > > Hi Bjorn, > After add "pci=pcie_bus_safe" boot options, Hot-plug for FC card is OK. > It's great! Thanks for your help! > > Giri, it's not the fc card problem, we fix this problem by add boot option > "pci=pcie_bus_safe" which force the MPS of the entire system to the smallest > possible. That's OK for a workaround, but it'd definitely not a complete solution. At the very least, we need some kind of info in dmesg that will enable us to diagnose the problem next time somebody runs into it. *You* are sophisticated enough to poke around and look at MPS settings manually, but the next person who runs into it will not be. -- 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
