Hi Xiongzi, Try qemu monitor to hot device add/remove that works. I think libvirt support is yet to be added.
One issue I faced was that I had to add a pcie root to move virtiofs device off pcie.0 and then hot add remove functionality works. So I had to add pcie root port by adding following to qemu command line. -device pcie-root-port,id=root1,slot=0 And now you can hot add a device using device_add. (qemu) device_add vhost-user-fs-pci,bus=root1,id=myvirtiofs,chardev=char0,tag=myfs,queue-size=1024 - To hot remove device, issue from qemu monitor. (qemu) device_del <device_id> ex. device_del myvirtiofs Thanks Vivek On Mon, May 03, 2021 at 12:50:56PM +0000, Ge, Xiongzi wrote: > Thanks, Stefan! > It seems that libvirt does not support device-attach for filesystem type > device, like virtiofs. Are there any other ways to do this hot-unplugging? > > Xiongzi > > On 4/8/21, 12:21 PM, "Stefan Hajnoczi" <[email protected]> wrote: > > On Wed, Apr 07, 2021 at 06:05:29PM +0000, Ge, Xiongzi wrote: > > Thanks Dr Gilbert, Vivek, Stefan, Greg! > > I put together the discussion into this thread and CC > [email protected]. > > > > Problem: > > Current Virtio-FS does not support live migration. Even when the > virtiofs directory is not mounted on the guest, VM cannot do live migration. > Any suggestions/interest If we want to make this work so we can still have > the live migration feature for other purpose on that VM? > > > > If we already have a shared file system like Ceph, does this make it > different? > > (Marc-André: I CCed you regarding D-Bus VMState, see below.) > > During the last virtio-fs call on Wednesday we discussed how to allow > live migration when the file system is not mounted. This means live > migration of a mounted file system still wouldn't be supported, but at > least it would be possible to migrate when the file system is not > mounted. > > The easiest way to do that is to hot unplug the vhost-user-fs-pci device > so that QEMU can live migrate the VM and then hot plug the > vhost-user-fs-pci device again after migration has completed. This > requires either manually performing the hot plug operations or some > automation to do this around live migration. > > A smoother approach would be for QEMU to allow live migration when the > file system is not mounted. Unfortunately it turns out this is actually > rather involved because virtiofsd runs as a separate process from QEMU > and the live migration interface for vhost-user devices is currently > pretty basic > (https://qemu.readthedocs.io/en/latest/interop/dbus-vmstate.html). There > is currently no way for virtiofsd to communicate with QEMU to allow/deny > live migration depending on whether virtiofsd currently has an active > FUSE session (mount). It might be possible to extend the D-Bus VMState > interface and implement support for "migration blockers" as they are > known in QEMU, but I wonder whether it's not better to just work on > full virtio-fs live migration instead. Either task is complex and I > wouldn't recommend it as a first contribution to virtiofsd or QEMU. > > Can you make use of the hotplug approach to live migration? > > Stefan > _______________________________________________ Virtio-fs mailing list [email protected] https://listman.redhat.com/mailman/listinfo/virtio-fs
