参考

• A study of the Linux kernel PCI subsystem with QEMU
• How to emulate block devices with QEMU

实验

建立下面的PCI总线拓扑，然后来模拟scsi磁盘的添加和删除

• PCI总线拓扑

root@ubuntu-vm:~# lspci -tv
-[0000:00]-+-00.0  Intel Corporation 440FX - 82441FX PMC [Natoma]
           +-01.0  Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
           +-01.1  Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
           +-01.3  Intel Corporation 82371AB/EB/MB PIIX4 ACPI
           +-02.0  Device 1234:1111
           +-03.0  Red Hat, Inc. Virtio filesystem
           +-04.0  Red Hat, Inc. Virtio network device
           +-05.0  Red Hat, Inc. Virtio block device
           +-06.0  Red Hat, Inc. Virtio block device
           \-07.0-[01]--+-03.0  Red Hat, Inc. Virtio SCSI
                        \-04.0  Red Hat, Inc. Virtio SCSI

• 实验用的块设备

root@ubuntu-vm:~# ls /sys/block/ -l
lrwxrwxrwx 1 root root 0 Sep  1 16:37 sda -> ../devices/pci0000:00/0000:00:07.0/0000:01:03.0/virtio4/host0/target0:0:0/0:0:0:0/block/sda
lrwxrwxrwx 1 root root 0 Sep  1 16:34 sdb -> ../devices/pci0000:00/0000:00:07.0/0000:01:04.0/virtio5/host1/target1:0:0/1:0:0:0/block/sdb

步骤

启动虚拟机的命令

qemu-system-x86_64 \
        -m 2G \
        -smp 4 \
        --kernel "./linux-6.4/arch/x86_64/boot/bzImage" \
        --append "noinitrd rootfstype=ext4 root=/dev/vda rw console=ttyS0" \
        --nographic \
        -fsdev local,security_model=passthrough,id=fsdev0,path=./share \
        -device virtio-9p-pci,id=fs0,fsdev=fsdev0,mount_tag=hostshare \
        -netdev user,id=eth0,hostfwd=tcp::8765-:22 -device virtio-net-pci,netdev=eth0 \
        -drive if=none,file=./slave2.qcow2,format=qcow2,id=hd0 \
        -device virtio-blk-pci,drive=hd0 \
        -drive if=none,file=./test_disk.qcow2,format=qcow2,id=hd1 \
        -device virtio-blk-pci,drive=hd1,num-queues=2 \
        --enable-kvm \
        \
        -device pci-bridge,id=bridge0,chassis_nr=2 \
        -device virtio-scsi-pci,id=scsi0,bus=bridge0,addr=0x3 \
        -device scsi-hd,drive=hd2,bus=scsi0.0 \
        -drive if=none,file=./test_disk2.qcow2,format=qcow2,id=hd2 \
        -device virtio-scsi-pci,id=scsi1,bus=bridge0,addr=0x4 \
        -device scsi-hd,drive=hd3,bus=scsi1.0 \
        -drive if=none,file=./test_disk3.qcow2,format=qcow2,id=hd3 \

查看scsi磁盘

root@ubuntu-vm:~# lsscsi -v
[0:0:0:0]    disk    QEMU     QEMU HARDDISK    2.5+  /dev/sda
  dir: /sys/bus/scsi/devices/0:0:0:0  [/sys/devices/pci0000:00/0000:00:07.0/0000:01:03.0/virtio4/host0/target0:0:0/0:0:0:0]
[1:0:0:0]    disk    QEMU     QEMU HARDDISK    2.5+  /dev/sdb
  dir: /sys/bus/scsi/devices/1:0:0:0  [/sys/devices/pci0000:00/0000:00:07.0/0000:01:04.0/virtio5/host1/target1:0:0/1:0:0:0]

剔除和增加

方法1

• 剔除

# echo 1 > /sys/block/sda/device/delete
# echo 1 > /sys/bus/pci/devices/0000\:00\:07.0/0000\:01\:03.0/remove

此时只剩下sdb：

# lsscsi
[1:0:0:0]    disk    QEMU     QEMU HARDDISK    2.5+  /dev/sdb

• 添加

# echo 1 > /sys/bus/pci/devices/0000\:00\:07.0/rescan

可以看到，sda又被添加回来：

# lsscsi
[0:0:0:0]    disk    QEMU     QEMU HARDDISK    2.5+  /dev/sda
[1:0:0:0]    disk    QEMU     QEMU HARDDISK    2.5+  /dev/sdb

方法2

• 剔除

# echo 1 > /sys/block/sda/device/delete

此时只剩下sdb：

# lsscsi
[1:0:0:0]    disk    QEMU     QEMU HARDDISK    2.5+  /dev/sdb

• 添加

# echo 1 > /sys/class/scsi_host/host0/scan

可以看到，sda又被添加回来：

# lsscsi
[0:0:0:0]    disk    QEMU     QEMU HARDDISK    2.5+  /dev/sda
[1:0:0:0]    disk    QEMU     QEMU HARDDISK    2.5+  /dev/sdb

完。