On Sun, Sep 08, 2019 at 07:53:55PM +0800, piaojun wrote:
> 
> 
> On 2019/9/6 19:52, Miklos Szeredi wrote:
> > On Fri, Sep 6, 2019 at 12:36 PM Stefan Hajnoczi <stefanha@redhat.com> wrote:
> >>
> >> On Fri, Sep 06, 2019 at 10:15:14AM +0200, Miklos Szeredi wrote:
> >>> On Thu, Sep 5, 2019 at 9:49 PM Vivek Goyal <vgoyal@redhat.com> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> Michael Tsirkin pointed out issues w.r.t various locking related TODO
> >>>> items and races w.r.t device removal.
> >>>>
> >>>> In this first round of cleanups, I have taken care of most pressing
> >>>> issues.
> >>>>
> >>>> These patches apply on top of following.
> >>>>
> >>>> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git#virtiofs-v4
> >>>>
> >>>> I have tested these patches with mount/umount and device removal using
> >>>> qemu monitor. For example.
> >>>
> >>> Is device removal mandatory?  Can't this be made a non-removable
> >>> device?  Is there a good reason why removing the virtio-fs device
> >>> makes sense?
> >>
> >> Hot plugging and unplugging virtio PCI adapters is common.  I'd very
> >> much like removal to work from the beginning.
> > 
> > Can you give an example use case?
> 
> I think VirtFS migration need hot plugging, or it may cause QEMU crash
> or some problems.

Live migration is currently unsupported.  Hot unplugging the virtio-fs
device would allow the guest to live migrate successfully, so it's a
useful feature to work around the missing live migration support.

Is this what you mean?

Stefan