Important to understand that after modifying and saving configuration of xml with virsh edit $name_of_guest
when i reenter the xml i can't see the iothread configuration in there. don't understand why.
Also, after add what you suggested I checked with "info qtree" command on the guest looking for sign of data-plane is working,
dev: virtio-blk-pci, id "virtio-disk1"
class = 0 (0x0)
ioeventfd = true
vectors = 2 (0x2)
virtio-pci-bus-master-bug-migration = false
disable-legacy = false
disable-modern = true
migrate-extra = false
modern-pio-notify = false
x-disable-pcie = false
addr = 07.0
romfile = ""
rombar = 1 (0x1)
multifunction = false
command_serr_enable = true
class SCSI controller, addr 00:07.0, pci id 1af4:1001 (sub 1af4:0002)
bar 0: i/o at 0xc0c0 [0xc0ff]
bar 1: mem at 0xfebf3000 [0xfebf3fff]
bus: virtio-bus
type virtio-pci-bus
dev: virtio-blk-device, id ""
drive = "drive-virtio-disk1"
logical_block_size = 512 (0x200)
physical_block_size = 512 (0x200)
min_io_size = 0 (0x0)
opt_io_size = 0 (0x0)
discard_granularity = 4294967295 (0xffffffff)
cyls = 16383 (0x3fff)
heads = 16 (0x10)
secs = 63 (0x3f)
serial = ""
config-wce = true
scsi = true
request-merging = true
indirect_desc = true
event_idx = true
notify_on_empty = true
any_layout = false
dev: virtio-blk-pci, id "virtio-disk0"
class = 0 (0x0)
ioeventfd = true
vectors = 2 (0x2)
virtio-pci-bus-master-bug-migration = false
disable-legacy = false
disable-modern = true
migrate-extra = false
modern-pio-notify = false
x-disable-pcie = false
addr = 04.0
romfile = ""
rombar = 1 (0x1)
multifunction = false
command_serr_enable = true
class SCSI controller, addr 00:04.0, pci id 1af4:1001 (sub 1af4:0002)
bar 0: i/o at 0xc040 [0xc07f]
bar 1: mem at 0xfebf1000 [0xfebf1fff]
bus: virtio-bus
type virtio-pci-bus
dev: virtio-blk-device, id ""
drive = "drive-virtio-disk0"
logical_block_size = 512 (0x200)
physical_block_size = 512 (0x200)
min_io_size = 0 (0x0)
opt_io_size = 0 (0x0)
discard_granularity = 4294967295 (0xffffffff)
cyls = 16383 (0x3fff)
heads = 16 (0x10)
secs = 63 (0x3f)
serial = ""
config-wce = true
scsi = false
request-merging = true
indirect_desc = true
event_idx = true
notify_on_empty = true
any_layout = false
dev: virtio-scsi-pci, id "scsi1"
ioeventfd = true
vectors = 4 (0x4)
virtio-pci-bus-master-bug-migration = false
disable-legacy = false
disable-modern = true
migrate-extra = false
modern-pio-notify = false
x-disable-pcie = false
addr = 08.0
romfile = ""
rombar = 1 (0x1)
multifunction = false
command_serr_enable = true
class SCSI controller, addr 00:08.0, pci id 1af4:1004 (sub 1af4:0008)
bar 0: i/o at 0xc100 [0xc13f]
bar 1: mem at 0xfebf4000 [0xfebf4fff]
bus: virtio-bus
type virtio-pci-bus
dev: virtio-scsi-device, id ""
num_queues = 1 (0x1)
max_sectors = 65535 (0xffff)
cmd_per_lun = 128 (0x80)
hotplug = true
param_change = true
indirect_desc = true
event_idx = true
notify_on_empty = true
any_layout = true
bus: scsi1.0
type SCSI
dev: scsi-block, id "scsi1-0-0-0"
drive = "drive-scsi1-0-0-0"
channel = 0 (0x0)
scsi-id = 0 (0x0)
lun = 0 (0x0)