[Pkg-rust-maintainers] Bug#1109051: virtiofsd: Unable to share folders to qemu:///session VMs with virtiofsd: Connection refused to socket

[Michael Tokarev]

On 10.07.2025 15:53, Gianpaolo wrote:
> Package: virtiofsd
> Version: 1.13.0-5+b1
> Severity: important
> X-Debbugs-Cc: gianpaoloc at gmail.com
> 
> Dear Maintainer,
> using virt-manager I created a Windows11 VM as a user (qemu:///session). Everything works fine (the VM can be launched and works) until I setup a shared folder using virtiofsd:
> 
> <filesystem type="mount" accessmode="passthrough">
>    <driver type="virtiofs"/>
>    <source dir="/tmp"/>
>    <target dir="host_tmp"/>
>    <address type="pci" domain="0x0000" bus="0x06" slot="0x00" function="0x0"/>
> </filesystem>
> 
> Under this condition the VM does not start anymore, with the error reported below. Notice that, the exact same VM, with the same configuration and shared folder, works when created in the system channel (qemu:///system).
> 
> The error reported by virt-manager is:
> Error starting domain: internal error: process exited while connecting to monitor: 2025-07-10T09:08:24.760511Z qemu-system-x86_64: -chardev socket,id=chr-vu-fs0,path=/home/user/.config/libvirt/qemu/lib/domain-1-win11/fs0-fs.sock: Failed to connect to '/home/user/.config/libvirt/qemu/lib/domain-1-win11/fs0-fs.sock': Connection refused
> 
> Traceback (most recent call last):
>    File "/usr/share/virt-manager/virtManager/asyncjob.py", line 71, in cb_wrapper
>      callback(asyncjob, *args, **kwargs)
>      ~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
>    File "/usr/share/virt-manager/virtManager/asyncjob.py", line 107, in tmpcb
>      callback(*args, **kwargs)
>      ~~~~~~~~^^^^^^^^^^^^^^^^^
>    File "/usr/share/virt-manager/virtManager/object/libvirtobject.py", line 57, in newfn
>      ret = fn(self, *args, **kwargs)
>    File "/usr/share/virt-manager/virtManager/object/domain.py", line 1384, in startup
>      self._backend.create()
>      ~~~~~~~~~~~~~~~~~~~~^^
>    File "/usr/lib/python3/dist-packages/libvirt.py", line 1390, in create
>      raise libvirtError('virDomainCreate() failed')
> libvirt.libvirtError: internal error: process exited while connecting to monitor: 2025-07-10T09:08:24.760511Z qemu-system-x86_64: -chardev socket,id=chr-vu-fs0,path=/home/user/.config/libvirt/qemu/lib/domain-1-win11/fs0-fs.sock: Failed to connect to '/home/user/.config/libvirt/qemu/lib/domain-1-win11/fs0-fs.sock': Connection refused

I've no idea here, but it feels like it's a libvirt bug or it doesn't
work at all.  virtiofsd needs root privileges.  Whenever libvirt can
provide such privileges in qemu user session is a question to libvirt.
There's nothing I can do here from virtiofsd PoV.

/mjt