[Virtio-fs] virtiofs doesn't accept writable group permissions

[stefanx]

Hello,

virtiofs doesn't accept writable group permissions (Libvirt/KVM, guest vm and host vm have Ubuntu 22.04):

Libvirt XML (host vm):

    <filesystem type='mount' accessmode='passthrough'>
      <driver type='virtiofs'/>
      <source dir='/mnt/xyz'/>
      <target dir='mnt-xyz'/>
      <address type='pci' domain='0x0000' bus='0x08' slot='0x00' function='0x0'/>
    </filesystem>

/etc/fstab (guest vm):
```
mnt-xyz       /mnt/xyz            virtiofs rw,_netdev 0 0
```
In /mnt/xyz/123 I have write permissions at host vm, but not at guest vm. host vm and guest vm have the same LDAP users.

Any ideas ?

Thanks Stefan