IO thread

Enabled ``IO thread`` option is ignored when controler is other than VirtIO SCSI Single.

-device virtio-scsi-pci,id=scsihw0,bus=pci.0,addr=0x5 
 
-drive file=/dev/zvol/nvmpool/data/vm-701-disk-1,if=none,id=drive-scsi0,discard=on,format=raw,cache=none,aio=io_uring,detect-zeroes=unmap 
-device scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,rotation_rate=1,bootindex=100 
 
-drive file=/dev/zvol/hddpool/data/vm-701-disk-1,if=none,id=drive-scsi1,discard=on,format=raw,cache=none,aio=io_uring,detect-zeroes=unmap 
-device scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=1,drive=drive-scsi1,id=scsi1 
 
-drive file=/dev/zvol/nvmpool/data/vm-701-disk-0,if=none,id=drive-scsi2,discard=on,format=raw,cache=none,aio=io_uring,detect-zeroes=unmap 
-device scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=2,drive=drive-scsi2,id=scsi2,rotation_rate=1 

• ``virtio-scsi-single`` controller chosen which create separate SCSI controller for each drive
• I/O thread enabled on ``virtioscsi2``

-device virtio-scsi-pci,id=virtioscsi0,bus=pci.3,addr=0x1 
-drive file=/dev/zvol/hddpool/data/vm-601-disk-0,if=none,id=drive-scsi0,cache=writeback,discard=on,format=raw,aio=io_uring,detect-zeroes=unmap 
-device scsi-hd,bus=virtioscsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0,bootindex=100 
 
-device virtio-scsi-pci,id=virtioscsi1,bus=pci.3,addr=0x2 
-drive file=/dev/zvol/hddpool/data/vm-601-disk-1,if=none,id=drive-scsi1,cache=writeback,discard=on,format=raw,aio=io_uring,detect-zeroes=unmap 
-device scsi-hd,bus=virtioscsi1.0,channel=0,scsi-id=0,lun=1,drive=drive-scsi1,id=scsi1 
 
-object iothread,id=iothread-virtioscsi2 
-device virtio-scsi-pci,id=virtioscsi2,bus=pci.3,addr=0x3,iothread=iothread-virtioscsi2 
-drive file=/dev/zvol/nvmpool/data/vm-601-disk-0,if=none,id=drive-scsi2,cache=writeback,discard=on,format=raw,aio=io_uring,detect-zeroes=unmap 
-device scsi-hd,bus=virtioscsi2.0,channel=0,scsi-id=0,lun=2,drive=drive-scsi2,id=scsi2