On Thu, 11 Jan 2018 10:23:32 +0800 sochin.jiang <sochin.ji...@huawei.com> wrote:
> On 2018/1/8 18:10, Greg Kurz wrote: > > On Tue, 19 Dec 2017 13:41:12 +0800 > > sochin.jiang <sochin.ji...@huawei.com> wrote: > > > >> Hi, guys. > >> > >> I'm looking for the hot-plug/unplug features of virtio-9p device > >> recently, and found there's a lack of support. > >> > >> I am wondering why ? Is there a reason. Actually, I write a qmp > >> command to support fsdev_add, then a device_add qmp will > >> > >> successfully add a virtio-9p device(just like virtio-blk). > >> > >> Whether there is some concerns that we haven't support this ? hope for > >> a reply, thanks. > >> > >> > >> sochin. > >> > > Hi Sochin, > > > > I've just discovered this mail by chance. Please note I'm the only active > > maintainer for virtio-9p. You really should check the content of MAINTAINERS > > and Cc the appropriate people. :) > > > > Now, back to your question. Yes, there's only some partial support for > > hot-plug/unplug. Mostly because nobody cared to work on it I guess. > > > > So, indeed, we don't have fsdev_add/fsdev_del, ie, we can only rely on > > shared directories specified on the QEMU command line. > > > > On the virtio-9p device side, hotplug is supported, ie, device_add virtio-9p > > works as expected. > > > > Hot-unplug is different as it requires some coordination with the guest. The > > current status is that it requires the 9p shared directory to be unmounted > > in the guest: if you do device_del while the directory is mounted in a linux > > guest, you'll get these messages in the guest syslog: > > > > kernel:9pnet_virtio virtio2: p9_virtio_remove: waiting for device in use. > > > > If the 9p directory is unmounted at some point, then the hot unplug > > sequence will eventually succeed. > > > > But this shouldn't be done like this: the guest should cancel inflight > > requests and cause any new I/O requests in the guest to fail right away. > > I have a tentative patch for the linux driver I can share if you want. > > > > Cheers, > > > > -- > > Greg > > > > . > > > > > Thanks, Greg. > > Indeed, I got those error messages while trying to do device_del with > shared directory mounted in the guest. I really would like to see you patch > for linux driver. > I'll try to send it soon. > About virtio-9p, we are actually considering to use it for hypervisor-based > container, Something like Intel's Clear Containers ? > a support of hotplug/unplug will be better, also I believe there will be more > people to work on it. That's good news ! Cheers, -- Greg > > > Sochin. > > >
