On 04/14/17 04:41, Shannon Zhao wrote: > Hi Laszlo, > > Thanks a lot for your reply:) > > On 2017/4/14 1:09, Laszlo Ersek wrote: >> Adding Andrea, Ard, Drew and Marcel; and the main qemu list >> >> On 04/13/17 09:37, Shannon Zhao wrote: >>> Hi, >>> >>> I'm testing the PCIe devices hotplug for ARM virt machine and using >>> ioh3420 as root port. I found that below command line could work. >>> >>> qemu-system-aarch64 -machine virt,accel=kvm,usb=off -cpu host -bios >>> QEMU_EFI.fd -m 12288 -smp 8,sockets=8,cores=1,threads=1 -device >>> ioh3420,port=0x8,chassis=1,id=pci.1,bus=pcie.0,addr=0x1 -device >>> ioh3420,port=0x9,chassis=2,id=pci.2,bus=pcie.0,addr=0x2 -device >>> ioh3420,port=0xa,chassis=3,id=pci.3,bus=pcie.0,addr=0x3 -device >>> ioh3420,port=0xb,chassis=4,id=pci.4,bus=pcie.0,addr=0x4 -device >>> ioh3420,port=0xc,chassis=5,id=pci.5,bus=pcie.0,addr=0x5 -device >>> ioh3420,port=0xd,chassis=6,id=pci.6,bus=pcie.0,addr=0x6 -device >>> ioh3420,port=0xe,chassis=7,id=pci.7,bus=pcie.0,addr=0x7 -device >>> ioh3420,port=0xf,chassis=8,id=pci.8,bus=pcie.0,addr=0x8 -device >>> ioh3420,port=0x10,chassis=9,id=pci.9,bus=pcie.0,addr=0x9 -device >>> ioh3420,port=0x11,chassis=10,id=pci.10,bus=pcie.0,addr=0xa -device >>> ioh3420,port=0x12,chassis=11,id=pci.11,bus=pcie.0,addr=0xb -device >>> ioh3420,port=0x13,chassis=12,id=pci.12,bus=pcie.0,addr=0xc -device >>> ioh3420,port=0x14,chassis=13,id=pci.13,bus=pcie.0,addr=0xd -device >>> i82801b11-bridge,id=pci.17,bus=pcie.0,addr=0x11 -device >>> pci-bridge,chassis_nr=18,id=pci.18,bus=pci.17,addr=0x0 -device >>> usb-ehci,id=usb,bus=pci.18,addr=0x1 -device >>> virtio-scsi-pci,id=scsi0,bus=pci.1,addr=0x0,disable-legacy=on,disable-modern=off >>> -drive >>> file=/mnt/sdb/guest.raw,format=raw,if=none,id=drive-scsi0-0-0-0,cache=none,aio=native >>> -device >>> scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1 >>> -netdev tap,id=hostnet1,vhost=on -device >>> virtio-net-pci,netdev=hostnet1,id=net1,mac=00:16:3e:2b:cc:e1,bus=pci.2,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet2,vhost=on -device >>> virtio-net-pci,netdev=hostnet2,id=net2,mac=00:16:3e:22:29:80,bus=pci.3,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet3,vhost=on -device >>> virtio-net-pci,netdev=hostnet3,id=net3,mac=00:16:3e:28:07:9a,bus=pci.4,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet4,vhost=on -device >>> virtio-net-pci,netdev=hostnet4,id=net4,mac=00:16:3e:3d:cd:b6,bus=pci.5,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet5,vhost=on -device >>> virtio-net-pci,netdev=hostnet5,id=net5,mac=00:16:3e:64:9f:b0,bus=pci.6,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet6,vhost=on -device >>> virtio-net-pci,netdev=hostnet6,id=net6,mac=00:16:3e:33:5b:d3,bus=pci.7,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet7,vhost=on -device >>> virtio-net-pci,netdev=hostnet7,id=net7,mac=00:16:3e:39:7c:df,bus=pci.8,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet8,vhost=on -device >>> virtio-net-pci,netdev=hostnet8,id=net8,mac=00:16:3e:0a:c1:4e,bus=pci.9,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet9,vhost=on -device >>> virtio-net-pci,netdev=hostnet9,id=net9,mac=00:16:3e:0a:58:a6,bus=pci.10,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet10,vhost=on -device >>> virtio-net-pci,netdev=hostnet10,id=net10,mac=00:16:3e:35:b5:80,bus=pci.11,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet11,vhost=on -device >>> virtio-net-pci,netdev=hostnet11,id=net11,mac=00:16:3e:4d:b5:bb,bus=pci.12,addr=0x0,disable-legacy=on,disable-modern=off >>> -netdev tap,id=hostnet12,vhost=on -device >>> virtio-net-pci,netdev=hostnet12,id=net12,mac=00:16:3e:3b:69:e9,bus=pci.13,addr=0x0,disable-legacy=on,disable-modern=off >>> -nographic >>> >>> But if I add one more ioh3420 device by appending above command with >>> "-device ioh3420,port=0x15,chassis=14,id=pci.14,bus=pcie.0,addr=0xe", >>> the guest can't boot. It seems that the firmware doesn't recognize the >>> PCIe devices and print "Connect: PciRoot(0x0): Not Found". >>> >>> I'm using QEMU 2.8.1 and edk2 at commit 36a0d5c. Is there any limitation >>> of the supported PCIe devices? >> >> In one sentence: you are running out of (emulated) IO space. >> >> Aarch64 does not have "IO space", but with QEMU, using the "virt" >> machine type, we emulate 64KB of IO space, mapped to a special MMIO >> range. This is available for PCI resource allocation, for such devices >> that have IO BARs (and for such PCI bridges that reserve IO space for >> hotplug purposes). >> >> The ioh3420 PCI Express Root Port device represents such a bridge. Even >> if you plug a PCI Express device into it that has only MMIO BARs, the >> bridge still advertises IO support, and it causes the firmware (and/or >> Linux) to reserve 4KB of IO space. With ~15-16 such ports, you run out >> of the 64 KB IO aperture, and the resource assignment fails. >> > So currently if we want to support more than ~15 virtio-net-pci devices, > they can't connect to root port.
Right. > They should connect to pcie root bus > directly, right? Correct, that will make them integrated endpoints, and no PCI Express ports will be necessary (hence no IO space will be wasted). > But this will not support hot-plug/remove. Correct. > > BTW, I think even though the qemu assign more than ~15 root port, I > think the firmware should enable the first 15 ports and continue to work > instead of failing with silence. PCI device enumeration & resource assignment are implemented in "MdeModulePkg/Bus/Pci/PciBusDxe". It is a generic edk2 driver that is built into OVMF, ArmVirtQemu, and (supposedly) most physical platform firmware, without any changes. If you have improvements in mind, please submit a patch for that driver. > >> The solution to this problem comes together from several parts: >> >> (1) New, vendor-independent device models in QEMU, for PCI Express Root >> Ports and Downstream Ports, that (optionally) do not advertise any >> support at all for IO BARs. This is on Marcel's task list. Please refer to: >> >> generic port device model: >> https://bugzilla.redhat.com/show_bug.cgi?id=1390316 >> > I see this is in upstream qemu. Yes. All of the pertaining work will be implemented upstream first. > >> optional disablement of IO space: >> https://bugzilla.redhat.com/show_bug.cgi?id=1344299 >> > Marcel, what's the status of this feature? (I think Marcel plans to answer your question, but AIUI he too might have a bit of post-vacation email backlog to flush.) Thanks Laszlo