Dear Maintainer,

After upgrading from 1.14.0-1 which works fine, to 1.14.0-2, I can now
not mount any virtiofs shares on Sid (tried on 2 different Trixie guests).

Error from virt-manager:

Error starting domain: internal error: QEMU unexpectedly closed the monitor
(vm='debian13'): 2026-08-11T10:15:39.842604Z qemu-system-x86_64: -device
{"driver":"vhost-user-fs-pci","id":"fs0","chardev":"chr-vu-
fs0","tag":"kernel","bus":"pci.2","addr":"0x0"}: Failed to read msg header.
Read 0 instead of 12. Original request 0.
2026-08-11T10:15:39.842685Z qemu-system-x86_64: -device
{"driver":"vhost-user-
fs-pci","id":"fs0","chardev":"chr-vu-
fs0","tag":"kernel","bus":"pci.2","addr":"0x0"}: vhost_backend_init failed:
Protocol error

Traceback (most recent call last):
   File "/usr/share/virt-manager/virtManager/asyncjob.py", line 67, in
cb_wrapper
     callback(asyncjob, *args, **kwargs)
     ~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
   File "/usr/share/virt-manager/virtManager/asyncjob.py", line 101, 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
1446, in
startup
     self._backend.create()
     ~~~~~~~~~~~~~~~~~~~~^^
   File "/usr/lib/python3/dist-packages/libvirt.py", line 1401, in create
     raise libvirtError('virDomainCreate() failed')
libvirt.libvirtError: internal error: QEMU unexpectedly closed the monitor
(vm='debian13'): 2026-08-11T10:15:39.842604Z qemu-system-x86_64: -device
{"driver":"vhost-user-fs-pci","id":"fs0","chardev":"chr-vu-
fs0","tag":"kernel","bus":"pci.2","addr":"0x0"}: Failed to read msg header.
Read 0 instead of 12. Original request 0.
2026-08-11T10:15:39.842685Z qemu-system-x86_64: -device
{"driver":"vhost-user-
fs-pci","id":"fs0","chardev":"chr-vu-
fs0","tag":"kernel","bus":"pci.2","addr":"0x0"}: vhost_backend_init failed:
Protocol error

Or on the CLI:

$ virsh attach-device debian13  virtiofs-kernel.xml --live

error: Failed to attach device from virtiofs-kernel.xml
error: internal error: unable to execute QEMU command 'device_add':
vhost_backend_init failed: Protocol error

Here's my virtiofs-kernel.xml:

<filesystem type="mount" accessmode="passthrough">
   <driver type="virtiofs"/>
   <binary path="/usr/libexec/virtiofsd"/>
   <idmap>
     <uid start="502" target="502" count="1"/>
     <gid start="502" target="502" count="1"/>
   </idmap>
   <source dir="/home/simon/kernel"/>
   <target dir="kernel"/>
</filesystem>

I've not changed anything else and downgrading to 1.14.0-1 works fine again.

I can confirm this observation and seeing the same error messages here.
Also downgrading to 1.14.0-1 and all works as expected again. Both
stable, testing and unstable guests is hit by this bug.

We believe that the bug you reported is fixed in the latest version of
rust-virtiofsd, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1144050@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Fabian Grünbichler <debian@fabian.gruenbichler.email> (supplier of updated rust-virtiofsd package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Thu, 13 Aug 2026 22:39:31 +0200
Source: rust-virtiofsd
Architecture: source
Version: 1.14.0-3
Distribution: unstable
Urgency: medium
Maintainer: Debian Rust Maintainers <pkg-rust-maintainers@alioth-lists.debian.net>
Changed-By: Fabian Grünbichler <debian@fabian.gruenbichler.email>
Closes: 1144050
Changes:
 rust-virtiofsd (1.14.0-3) unstable; urgency=medium
 .
   * Package virtiofsd 1.14.0 from crates.io using debcargo 2.8.4
   * Update seccomp filter to match vhost 0.17 (Closes: #1144050)
   * Update mkosi autopkgtest to pick up unsigned systemd-boot efi files
Checksums-Sha1:
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 27c05bfec0503e9ada373c4a8c734321f5848cfa 8660 rust-virtiofsd_1.14.0-3.debian.tar.xz
 3a75d71ca76cf2d9cb363fcaecc4006fc5ae0d36 7674 rust-virtiofsd_1.14.0-3_source.buildinfo
Checksums-Sha256:
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 fc1b57e9afc32cd09adff8d1d4bc55e67d983c04410d115e6349c74a3d53d664 8660 rust-virtiofsd_1.14.0-3.debian.tar.xz
 868596ed9bd3e8387b4bd3c38e2a60657c684f307f39cb62abb8295a8cfa1cff 7674 rust-virtiofsd_1.14.0-3_source.buildinfo
Files:
 a5ea27826ce653a7181431b53e15db0f 3571 otherosfs optional rust-virtiofsd_1.14.0-3.dsc
 011bdbe3b566672632e50e8f639d1d63 8660 otherosfs optional rust-virtiofsd_1.14.0-3.debian.tar.xz
 a2a09614517b55fd14b9a163a8eda710 7674 otherosfs optional rust-virtiofsd_1.14.0-3_source.buildinfo
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