On Mon, Sep 09, 2019 at 06:14:55PM +0200, Stefan Hajnoczi wrote: > 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@xxxxxxxxxx> 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@xxxxxxxxxx> 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 Exactly. That's what I also said. To add to that, hotplug can not be negotiated, so it's not a feature we can easily add down the road if old guests crash on unplug. Thus a driver that does not support unplug should not claim to support removal. -- MST
