<memoryBacking>
    <access mode='shared'/>
  </memoryBacking>

... ...
 <disk type='vhostvdpa' device='disk'>
      <driver name='qemu' type='raw' cache='directsync' io='threads' copy_on_read='on' discard='unmap' detect_zeroes='on'/>
      <source dev='/dev/vhost-vdpa-0'/>
      <target dev='vdb' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
    </disk>
  </devices>

 -add-fd set=0,fd=20,opaque=libvirt-1-storage-vdpa -blockdev {"driver":"virtio-blk-vhost-vdpa","path":"/dev/fdset/0","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap","cache":{"direct":true,"no-flush":false}} -blockdev {"node-name":"libvirt-1-format","read-only":false,"discard":"unmap","detect-zeroes":"on","cache":{"direct":true,"no-flush":false},"driver":"raw","file":"libvirt-1-storage"} -blockdev {"driver":"copy-on-read","node-name":"libvirt-CoR-vdb","file":"libvirt-1-format","discard":"unmap"} -device {"driver":"virtio-blk-pci","bus":"pci.7","addr":"0x0","drive":"libvirt-CoR-vdb","id":"virtio-disk1","write-cache":"off"}

[root@localhost ~]# lsblk 
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
vda           252:0    0   10G  0 disk 
├─vda1        252:1    0  600M  0 part /boot/efi
├─vda2        252:2    0    1G  0 part /boot
└─vda3        252:3    0  8.4G  0 part 
  ├─rhel-root 253:0    0  7.4G  0 lvm  /
  └─rhel-swap 253:1    0    1G  0 lvm  [SWAP]
vdb           252:16   0  128M  0 disk 
[root@localhost ~]# mkfs.ext4 /dev/vdb
mke2fs 1.46.5 (30-Dec-2021)
Discarding device blocks: done                            
Creating filesystem with 131072 1k blocks and 32768 inodes
Filesystem UUID: f7840b22-1e7a-4ca2-88c5-dbdf65add12d
Superblock backups stored on blocks: 
	8193, 24577, 40961, 57345, 73729

Allocating group tables: done                            
[   86.788732] I/O error, dev vdb, sector 262016 op 0x9:(WRITE_ZEROES) flags 0x8000800 phys_seg 0 prio class 2
[   86.788953] I/O error, dev vdb, sector 262016 op 0x1:(WRITE) flags 0x800 phys_seg 16 prio class 2
Writing inode tables: [   86.789104] I/O error, dev vdb, sector 262016 op 0x9:(WRITE_ZEROES) flags 0x800 phys_seg 0 prio class 2
[   86.793178] I/O error, dev vdb, sector 582 op 0x9:(WRITE_ZEROES) flags 0x8000800 phys_seg 0 prio class 2
done                            
[   86.794952] I/O error, dev vdb, sector 582 op 0x1:(WRITE) flags 0x800 phys_seg 1 prio class 2
[   86.795114] I/O error, dev vdb, sector 582 op 0x9:(WRITE_ZEROES) flags 0x800 phys_seg 0 prio class 2
[   86.800133] I/O error, dev vdb, sector 15968 op 0x9:(WRITE_ZEROES) flags 0x8000800 phys_seg 0 prio class 2
[   86.800324] I/O error, dev vdb, sector 15968 op 0x1:(WRITE) flags 0x800 phys_seg 1 prio class 2
[   86.800637] I/O error, dev vdb, sector 15968 op 0x9:(WRITE_ZEROES) flags 0x800 phys_seg 0 prio class 2
Creating journal (4096 blocks): [   86.811485] I/O error, dev vdb, sector 98306 op 0x9:(WRITE_ZEROES) flags 0x8000800 phys_seg 0 prio class 2
done
Writing superblocks and filesystem accounting information: [   86.826349] Buffer I/O error on dev vdb, logical block 12288, lost async page write
[   86.826354] Buffer I/O error on dev vdb, logical block 12289, lost async page write
[   86.826355] Buffer I/O error on dev vdb, logical block 12290, lost async page write
[   86.826356] Buffer I/O error on dev vdb, logical block 12291, lost async page write
[   86.826358] Buffer I/O error on dev vdb, logical block 12292, lost async page write
[   86.826358] Buffer I/O error on dev vdb, logical block 12293, lost async page write
[   86.826359] Buffer I/O error on dev vdb, logical block 12294, lost async page write
mkfs.ext4: [   86.826360] Buffer I/O error on dev vdb, logical block 12295, lost async page write
[   86.826361] Buffer I/O error on dev vdb, logical block 12296, lost async page write
Input/output error while writing out and closing file system
[   86.826362] Buffer I/O error on dev vdb, logical block 12297, lost async page write
[root@localhost ~]#