On Sat, Dec 08, 2018 at 11:58:59AM +0000, xuyandong wrote: > > Hi all, > > > > > > > > In our test, we configured VM with several pci-bridges and a > > virtio-net nic been attached with bus 4, > > > > After VM is startup, We ping this nic from host to judge if it is > > working normally. Then, we hot add pci devices to this VM with bus 0. > > > > We found the virtio-net NIC in bus 4 is not working (can not connect) > > occasionally, as it kick virtio backend failure with error below: > > > > Unassigned mem write 00000000fc803004 = 0x1 > > > > > > > > memory-region: pci_bridge_pci > > > > 0000000000000000-ffffffffffffffff (prio 0, RW): pci_bridge_pci > > > > 00000000fc800000-00000000fc803fff (prio 1, RW): virtio-pci > > > > 00000000fc800000-00000000fc800fff (prio 0, RW): > > virtio-pci-common > > > > 00000000fc801000-00000000fc801fff (prio 0, RW): virtio-pci-isr > > > > 00000000fc802000-00000000fc802fff (prio 0, RW): > > virtio-pci-device > > > > 00000000fc803000-00000000fc803fff (prio 0, RW): > > virtio-pci-notify <- io mem unassigned > > > > … > > > > > > > > We caught an exceptional address changing while this problem happened, > > show as > > follow: > > > > Before pci_bridge_update_mappings: > > > > 00000000fc000000-00000000fc1fffff (prio 1, RW): alias > > pci_bridge_pref_mem @pci_bridge_pci 00000000fc000000-00000000fc1fffff > > > > 00000000fc200000-00000000fc3fffff (prio 1, RW): alias > > pci_bridge_pref_mem @pci_bridge_pci 00000000fc200000-00000000fc3fffff > > > > 00000000fc400000-00000000fc5fffff (prio 1, RW): alias > > pci_bridge_pref_mem @pci_bridge_pci 00000000fc400000-00000000fc5fffff > > > > 00000000fc600000-00000000fc7fffff (prio 1, RW): alias > > pci_bridge_pref_mem @pci_bridge_pci 00000000fc600000-00000000fc7fffff > > > > 00000000fc800000-00000000fc9fffff (prio 1, RW): alias > > pci_bridge_pref_mem @pci_bridge_pci 00000000fc800000-00000000fc9fffff > > <- correct Adress Spce > > > > 00000000fca00000-00000000fcbfffff (prio 1, RW): alias > > pci_bridge_pref_mem @pci_bridge_pci 00000000fca00000-00000000fcbfffff > > > > 00000000fcc00000-00000000fcdfffff (prio 1, RW): alias > > pci_bridge_pref_mem @pci_bridge_pci 00000000fcc00000-00000000fcdfffff > > > > 00000000fce00000-00000000fcffffff (prio 1, RW): alias > > pci_bridge_pref_mem @pci_bridge_pci 00000000fce00000-00000000fcffffff > > > > > > > > After pci_bridge_update_mappings: > > > > 00000000fda00000-00000000fdbfffff (prio 1, RW): alias > > pci_bridge_mem @pci_bridge_pci 00000000fda00000-00000000fdbfffff > > > > 00000000fdc00000-00000000fddfffff (prio 1, RW): alias > > pci_bridge_mem @pci_bridge_pci 00000000fdc00000-00000000fddfffff > > > > 00000000fde00000-00000000fdffffff (prio 1, RW): alias > > pci_bridge_mem @pci_bridge_pci 00000000fde00000-00000000fdffffff > > > > 00000000fe000000-00000000fe1fffff (prio 1, RW): alias > > pci_bridge_mem @pci_bridge_pci 00000000fe000000-00000000fe1fffff > > > > 00000000fe200000-00000000fe3fffff (prio 1, RW): alias > > pci_bridge_mem @pci_bridge_pci 00000000fe200000-00000000fe3fffff > > > > 00000000fe400000-00000000fe5fffff (prio 1, RW): alias > > pci_bridge_mem @pci_bridge_pci 00000000fe400000-00000000fe5fffff > > > > 00000000fe600000-00000000fe7fffff (prio 1, RW): alias > > pci_bridge_mem @pci_bridge_pci 00000000fe600000-00000000fe7fffff > > > > 00000000fe800000-00000000fe9fffff (prio 1, RW): alias > > pci_bridge_mem @pci_bridge_pci 00000000fe800000-00000000fe9fffff > > > > fffffffffc800000-fffffffffc800000 (prio 1, RW): alias > > pci_bridge_pref_mem > > @pci_bridge_pci fffffffffc800000-fffffffffc800000 <- Exceptional Adress > Space > > This one is empty though right? > > > > > > > We have figured out why this address becomes this value, according to > > pci spec, pci driver can get BAR address size by writing 0xffffffff > > to > > > > the pci register firstly, and then read back the value from this register. > > > OK however as you show below the BAR being sized is the BAR if a bridge. Are > you then adding a bridge device by hotplug?
No, I just simply hot plugged a VFIO device to Bus 0, another interesting phenomenon is If I hot plug the device to other bus, this doesn't happened. > > > > We didn't handle this value specially while process pci write in > > qemu, the function call stack is: > > > > Pci_bridge_dev_write_config > > > > -> pci_bridge_write_config > > > > -> pci_default_write_config (we update the config[address] value here > > -> to > > fffffffffc800000, which should be 0xfc800000 ) > > > > -> pci_bridge_update_mappings > > > > ->pci_bridge_region_del(br, br->windows); > > > > -> pci_bridge_region_init > > > > -> > > pci_bridge_init_alias (here pci_bridge_get_base, we use the wrong > > value > > fffffffffc800000) > > > > -> > > memory_region_transaction_commit > > > > > > > > So, as we can see, we use the wrong base address in qemu to update the > > memory regions, though, we update the base address to > > > > The correct value after pci driver in VM write the original value > > back, the virtio NIC in bus 4 may still sends net packets concurrently > > with > > > > The wrong memory region address. > > > > > > > > We have tried to skip the memory region update action in qemu while > > detect pci write with 0xffffffff value, and it does work, but > > > > This seems to be not gently. > > For sure. But I'm still puzzled as to why does Linux try to size the BAR of > the > bridge while a device behind it is used. > > Can you pls post your QEMU command line? My QEMU command line: /root/xyd/qemu-system-x86_64 -name guest=Linux,debug-threads=on -S -object secret,id=masterKey0,format=raw,file=/var/run/libvirt/qemu/domain-194-Linux/master-key.aes -machine pc-i440fx-2.8,accel=kvm,usb=off,dump-guest-core=off -cpu host,+kvm_pv_eoi -bios /usr/share/OVMF/OVMF.fd -m size=4194304k,slots=256,maxmem=33554432k -realtime mlock=off -smp 20,sockets=20,cores=1,threads=1 -numa node,nodeid=0,cpus=0-4,mem=1024 -numa node,nodeid=1,cpus=5-9,mem=1024 -numa node,nodeid=2,cpus=10-14,mem=1024 -numa node,nodeid=3,cpus=15-19,mem=1024 -uuid 34a588c7-b0f2-4952-b39c-47fae3411439 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/run/libvirt/qemu/domain-194-Linux/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-hpet -global kvm-pit.lost_tick_policy=delay -no-shutdown -boot strict=on -device pci-bridge,chassis_nr=1,id=pci.1,bus=pci.0,addr=0x8 -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.0,addr=0x9 -device pci-bridge,chassis_nr=3,id=pci.3,bus=pci.0,addr=0xa -device pci-bridge,chassis_nr=4,id=pci.4,bus=pci.0,addr=0xb -device pci-bridge,chassis_nr=5,id=pci.5,bus=pci.0,addr=0xc -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device usb-ehci,id=usb1,bus=pci.0,addr=0x10 -device nec-usb-xhci,id=usb2,bus=pci.0,addr=0x11 -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x3 -device virtio-scsi-pci,id=scsi1,bus=pci.0,addr=0x4 -device virtio-scsi-pci,id=scsi2,bus=pci.0,addr=0x5 -device virtio-scsi-pci,id=scsi3,bus=pci.0,addr=0x6 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x7 -drive file=/mnt/sdb/xml/centos_74_x64_uefi.raw,format=raw,if=none,id=drive-virtio-disk0,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x2,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -drive if=none,id=drive-ide0-1-1,readonly=on,cache=none -device ide-cd,bus=ide.1,unit=1,drive=drive-ide0-1-1,id=ide0-1-1 -netdev tap,fd=35,id=hostnet0 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:89:5d:8b,bus=pci.4,addr=0x1 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -device usb-tablet,id=input0,bus=usb.0,port=1 -vnc 0.0.0.0:0 -device cirrus-vga,id=video0,vgamem_mb=8,bus=pci.0,addr=0x12 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0xd -msg timestamp=on I am also very curious about this issue, in the linux kernel code, maybe double check in function pci_bridge_check_ranges triggered this problem. > > > > > > > > > diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c > > > > index b2e50c3..84b405d 100644 > > > > --- a/hw/pci/pci_bridge.c > > > > +++ b/hw/pci/pci_bridge.c > > > > @@ -256,7 +256,8 @@ void pci_bridge_write_config(PCIDevice *d, > > > > pci_default_write_config(d, address, val, len); > > > > - if (ranges_overlap(address, len, PCI_COMMAND, 2) || > > > > + if ( (val != 0xffffffff) && > > > > + (ranges_overlap(address, len, PCI_COMMAND, 2) || > > > > /* io base/limit */ > > > > ranges_overlap(address, len, PCI_IO_BASE, 2) || > > > > @@ -266,7 +267,7 @@ void pci_bridge_write_config(PCIDevice *d, > > > > ranges_overlap(address, len, PCI_MEMORY_BASE, 20) || > > > > /* vga enable */ > > > > - ranges_overlap(address, len, PCI_BRIDGE_CONTROL, 2)) { > > > > + ranges_overlap(address, len, PCI_BRIDGE_CONTROL, 2))) { > > > > pci_bridge_update_mappings(s); > > > > } > > > > > > > > Thinks, > > > > Xu > >