【软件信息】
1、内核版本：5.10.0-60.93.0.118.oe2203.loongarch64
2、系统版本：openEuler release 22.03 LTS
3、qemu版本：qemu-6.2.0-65.oe2203
【复现步骤】

1. 启动虚拟机
   MALLOC_PERTURB_=1 /usr/libexec/qemu-kvm
   -name 'avocado-vt-vm1'
   -machine loongson7a
   -device pcie-root-port,id=pcie-root-port-0,multifunction=on,bus=pcie.0,addr=0x1,chassis=1
   -device pcie-pci-bridge,id=pcie-pci-bridge-0,addr=0x0,bus=pcie-root-port-0
   -nodefaults
   -device qxl-vga,bus=pcie.0,addr=0x2
   -m 2048
   -smp 2,maxcpus=2,cores=1,threads=1,sockets=2
   -cpu 'Loongson-3A5000'
   -device pcie-root-port,id=pcie-root-port-1,port=0x1,addr=0x1.0x1,bus=pcie.0,chassis=2
   -device qemu-xhci,id=usb1,bus=pcie-root-port-1,addr=0x0
   -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1
   -device pcie-root-port,id=pcie-root-port-2,port=0x2,addr=0x1.0x2,bus=pcie.0,chassis=3
   -device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pcie-root-port-2,addr=0x0
   -blockdev node-name=file_image1,driver=file,filename=test.qcow2
   -blockdev node-name=drive_image1,driver=qcow2,file=file_image1
   -device scsi-hd,id=image1,drive=drive_image1
   -vnc :0
   -rtc base=utc,clock=host
   -boot menu=off,order=cdn,once=c,strict=off
   -net none
   -bios loongarch_bios.bin
   -enable-kvm
   -device pcie-root-port,id=pcie_extra_root_port_0,multifunction=on,bus=pcie.0,addr=0x3,chassis=4
   -monitor telnet:localhost:4444,server,nowait
   -serial stdio

2. 连接 qemu monitor，进行pci设备 增加/删除 操作
   [root@localhost ~]# telnet 127.0.0.1 4444
   Trying 127.0.0.1...
   Connected to 127.0.0.1.
   Escape character is '^]'.
   QEMU 4.2.0 monitor - type 'help' for more information
   (qemu)
   (qemu)
   (qemu) netdev_add tap,id=test-1
   (qemu) device_add virtio-net-pci,netdev=test-1,bus=pcie_extra_root_port_0,id=test-2
   (qemu)
   (qemu) device_del test-2
   (qemu) netdev_del test-1
   network script /etc/qemu-ifdown failed with status 256
   (qemu)
   (qemu)

3. 查看虚拟机lspci/ifconfig，用新增的网络设备ping
   [root@kvm-guest ~]#
   [root@kvm-guest ~]# ifconfig
   lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
   inet 127.0.0.1 netmask 255.0.0.0
   inet6 ::1 prefixlen 128 scopeid 0x10
   loop txqueuelen 1000 (Local Loopback)
   RX packets 0 bytes 0 (0.0 B)
   RX errors 0 dropped 0 overruns 0 frame 0
   TX packets 0 bytes 0 (0.0 B)
   TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

[root@kvm-guest ~]# lspci
00:00.0 Host bridge: Loongson Technology LLC Hyper Transport Bridge Controller
00:01.0 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:01.1 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:01.2 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:02.0 VGA compatible controller: Red Hat, Inc. QXL paravirtual graphic card (rev 04)
00:03.0 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
01:00.0 PCI bridge: Red Hat, Inc. Device 000e
03:00.0 USB controller: Red Hat, Inc. QEMU XHCI Host Controller (rev 01)
04:00.0 SCSI storage controller: Red Hat, Inc. Virtio SCSI (rev 01)
[root@kvm-guest ~]#
[root@kvm-guest ~]# [ 54.283890] pciehp 0000:00:03.0:pcie004: Slot(0-3): Attention button pressed
[ 54.285229] pciehp 0000:00:03.0:pcie004: Slot(0-3) Powering on due to button press
[ 54.286738] pciehp 0000:00:03.0:pcie004: Slot(0-3): Card present
[ 54.287869] pciehp 0000:00:03.0:pcie004: Slot(0-3): Link Up
[ 54.395202] pci 0000:05:00.0: BAR 4: assigned [mem 0x48e00000-0x48e03fff 64bit pref]
[ 54.396599] pci 0000:05:00.0: BAR 1: assigned [mem 0x48c00000-0x48c00fff]
[ 54.397814] pcieport 0000:00:03.0: PCI bridge to [bus 05]
[ 54.398755] pcieport 0000:00:03.0: bridge window [io 0x7000-0x7fff]
[ 54.403816] pcieport 0000:00:03.0: bridge window [mem 0x48c00000-0x48dfffff]
[ 54.407810] pcieport 0000:00:03.0: bridge window [mem 0x48e00000-0x48ffffff 64bit pref]
[ 54.414641] virtio-pci 0000:05:00.0: enabling device (0000 -> 0002)
[ 54.455641] virtio_net virtio1 enp5s0: renamed from eth0
[ 54.490894] IPv6: ADDRCONF(NETDEV_UP): enp5s0: link is not ready
[ 54.503053] IPv6: ADDRCONF(NETDEV_UP): enp5s0: link is not ready
[ 54.510791] IPv6: ADDRCONF(NETDEV_UP): enp5s0: link is not ready
[ 54.519976] IPv6: ADDRCONF(NETDEV_UP): enp5s0: link is not ready
[ 55.449578] IPv6: ADDRCONF(NETDEV_CHANGE): enp5s0: link becomes ready

[root@kvm-guest ~]# lspci
00:00.0 Host bridge: Loongson Technology LLC Hyper Transport Bridge Controller
00:01.0 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:01.1 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:01.2 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:02.0 VGA compatible controller: Red Hat, Inc. QXL paravirtual graphic card (rev 04)
00:03.0 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
01:00.0 PCI bridge: Red Hat, Inc. Device 000e
03:00.0 USB controller: Red Hat, Inc. QEMU XHCI Host Controller (rev 01)
04:00.0 SCSI storage controller: Red Hat, Inc. Virtio SCSI (rev 01)
05:00.0 Ethernet controller: Red Hat, Inc. Virtio network device (rev 01)
[root@kvm-guest ~]#
[root@kvm-guest ~]# ifconfig
enp5s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.122.76 netmask 255.255.255.0 broadcast 192.168.122.255
inet6 fe80::83c1:9637:350a:8329 prefixlen 64 scopeid 0x20
ether 52:54:00:12:34:56 txqueuelen 1000 (Ethernet)
RX packets 8 bytes 905 (905.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 26 bytes 3524 (3.4 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

[root@kvm-guest ~]#
[root@kvm-guest ~]# ping 192.168.122.1 -c 5
PING 192.168.122.1 (192.168.122.1) 56(84) bytes of data.
64 bytes from 192.168.122.1: icmp_seq=1 ttl=64 time=0.310 ms
64 bytes from 192.168.122.1: icmp_seq=2 ttl=64 time=0.152 ms
64 bytes from 192.168.122.1: icmp_seq=3 ttl=64 time=0.188 ms
64 bytes from 192.168.122.1: icmp_seq=4 ttl=64 time=0.160 ms
64 bytes from 192.168.122.1: icmp_seq=5 ttl=64 time=0.187 ms

--- 192.168.122.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4007ms
rtt min/avg/max/mdev = 0.152/0.199/0.310/0.058 ms
[root@kvm-guest ~]# [ 90.811356] pciehp 0000:00:03.0:pcie004: Slot(0-3): Attention button pressed
[ 90.812730] pciehp 0000:00:03.0:pcie004: Slot(0-3): Powering off due to button press

[root@kvm-guest ~]#
[root@kvm-guest ~]# lspci
00:00.0 Host bridge: Loongson Technology LLC Hyper Transport Bridge Controller
00:01.0 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:01.1 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:01.2 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
00:02.0 VGA compatible controller: Red Hat, Inc. QXL paravirtual graphic card (rev 04)
00:03.0 PCI bridge: Red Hat, Inc. QEMU PCIe Root port
01:00.0 PCI bridge: Red Hat, Inc. Device 000e
03:00.0 USB controller: Red Hat, Inc. QEMU XHCI Host Controller (rev 01)
04:00.0 SCSI storage controller: Red Hat, Inc. Virtio SCSI (rev 01)
[root@kvm-guest ~]# ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10
loop txqueuelen 1000 (Local Loopback)
RX packets 8 bytes 592 (592.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 8 bytes 592 (592.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0