Hi, > Subject: Re: [Question] Why doesn't PCIe hotplug work for Q35 machine? > > On Sun, 2014-08-17 at 13:00 +0200, Michael S. Tsirkin wrote: > > On Fri, Aug 15, 2014 at 07:33:29AM +0000, Gonglei (Arei) wrote: > > > Hi, > > > > > > I noticed that the qemu-2.1 release change log says > > > " PCIe: Basic hot-plug/hot-unplug support for Q35 machine." > > > And then I made a testing for the hotplugging function of Q35. > > > But I'm failed, and I got the dmesg log in guest os as below: > > > > > > [ 159.035250] Pciehp 0000:05:00.0:pcie24: Button pressed on Slot (0 - 4) > > > [ 159.035274] Pciehp 0000:05:00.0:pcie24: Card present on Slot (0 - 4) > > > [ 159.036517] Pciehp 0000:05:00.0:pcie24: PCI slot #0 - 4 - powering on > > > due > to button press. > > > [ 159.188049] Pciehp 0000:05:00.0:pcie24: Failed to check link status > > > [ 159.201968] Pciehp 0000:05:00.0:pcie24: Card not present on Slot (0 - 4) > > > [ 159.202529] Pciehp 0000:05:00.0:pcie24: Already disabled on Slot (0 - 4) > > > > > > Steps of testing: > > > > > > #1. QEMU version: > > > > > > The lateset master tree source. > > > > > > #2. Command line: > > > > > > ./qemu-system-x86_64 -enable-kvm -m 2048 -machine q35 -device > ide-drive,bus=ide.2,drive=MacHDD \ > > > -drive id=MacHDD,if=none,file=/mnt/sdb/gonglei/image/redhat_q35.img > -monitor stdio -vnc :10 -readconfig ../docs/q35-chipset.cfg > > > QEMU 2.0.93 monitor - type 'help' for more information > > > (qemu) device_add > virtio-net-pci,id=nic2,bus=pcie-switch-downstream-port-1-1,addr=1.0 > > > > I don't think you can use any slot except slot 0 for pci express.
OK. Does the PCIe specification say that? I appreciate very much that you explain more. > Indeed, only slot 0 can be used, try the same without specifying the addr > property. > OK, got it. Thank you so much. > > > (qemu) info network > > > hub 0 > > > \ user.0: index=0,type=user,net=10.0.2.0,restrict=off > > > \ e1000.0: index=0,type=nic,model=e1000,macaddr=52:54:00:12:34:56 > > > > > > #3. Guest OS: > > > > > > Both rhel-server-7.0-x86_64 and SLES-11-SP3-DVD-x86_64-GM. > > > > > > #4. Content of ../docs/q35-chipset.cfg: > > > > > > [snip] > > > > > > ## > > > # Example PCIe switch with two downstream ports > > > # > > > [device "pcie-switch-upstream-port-1"] > > > driver = "x3130-upstream" > > > bus = "ich9-pcie-port-4" > > > addr = "00.0" > > > > > > [device "pcie-switch-downstream-port-1-1"] > > > driver = "xio3130-downstream" > > > multifunction = "on" > > > bus = "pcie-switch-upstream-port-1" > > > addr = "00.0" > > > port = "1" > > > chassis = "5" > > > > > > [device "pcie-switch-downstream-port-1-2"] > > > driver = "xio3130-downstream" > > > multifunction = "on" > > > bus = "pcie-switch-upstream-port-1" > > > addr = "00.1" > > > port = "1" > > > chassis = "6" > > > > > > [device "ich9-ehci-1"] > > > driver = "ich9-usb-ehci1" > > > multifunction = "on" > > > bus = "pcie.0" > > > addr = "1d.7" > > > > > > [snip] > > > > > > BTW, except testing hotplug of downstream ports, I also test the root port > > > with "device_add virtio-net-pci,id=nic2,bus=ich9-pcie-port-1,addr=1.0", > > > but > > > I got the same result. > > > > Same thing. > Agreed, and also make sure that ich9-pcie-port-1 is a root port's bus and not > an upstream port's bus. > Yes, it is. > Thanks, > Marcel > > > > > > Am I wrong in some places? Or a QEMU bug? Thanks for any help. > > > > > > Best regards, > > > -Gonglei > > > > > > > We might want to add a check for this, to produce a > > better error message. > > > Work in progress. Thanks! I also find other questions. Will post in a patch series. Best regards, -Gonglei
