Debugging virtiofs

I can't seem to start a VM with virtiofs. Everything is running as root (unraid) with a pretty simple setup: <filesystem type='mount' accessmode='passthrough'> <driver type='virtiofs'/> <binary path='/usr/libexec/virtiofsd' /> <source dir='/mnt/user/shared'/> <target dir='shared_mount'/> </filesystem> Even with debug logging at max, all I get in the main log is: qemu-system-x86_64: -device vhost-user-fs-pci,chardev=chr-vu-fs0,tag=shared_mount,bus=pci.5,addr=0x0: Failed to write msg. Wrote -1 instead of 12. qemu-system-x86_64: -device vhost-user-fs-pci,chardev=chr-vu-fs0,tag=shared_mount,bus=pci.5,addr=0x0: vhost_dev_init failed: Operation not permitted shutting down, reason=failed And in the fsd log: [ID: 00029648] virtio_session_mount: Waiting for vhost-user socket connection... [ID: 00029648] virtio_session_mount: Received vhost-user socket connection [ID: 00000001] pivot_root(., .): Invalid argument Nothing else in any other logs (e.g. dmesg). What do these errors mean? How do I troubleshoot this?