[libvirt PATCH 0/3] Enable copy/paste for vnc displays

[Marc-André Lureau]

Hi

On Wed, Mar 23, 2022 at 6:44 PM Jonathon Jongsma <jjongsma at redhat.com> wrote:
>
> On 3/23/22 4:17 AM, Daniel P. Berrangé wrote:
> > On Wed, Mar 23, 2022 at 12:01:19PM +0400, Marc-André Lureau wrote:
> >> Hi
> >>
> >> On Wed, Mar 23, 2022 at 12:47 AM Jonathon Jongsma <jjongsma at redhat.com> wrote:
> >>>
> >>> This patch series enables support for the qemu-vdagent character device which
> >>> enables copy/paste support between guest and client when using vnc graphics.
> >>>
> >>> The guest must be configured with something like the following:
> >>>
> >>>      <channel type='qemu-vdagent'>
> >>>        <source clipboard='on' mouse='on'/>
> >>>        <target type='virtio' name='com.redhat.spice.0'/>
> >>>      </channel>
> >>>
> >>> Copy/paste sync requires a vnc client that has support for copy/paste commands.
> >>> Currently virt-viewer does not work, but the version of tigervnc provided by
> >>> fedora (executable name 'vncviewer') does work.
> >>>
> >>> More details about this device on Gerd's blog:
> >>> https://www.kraxel.org/blog/2021/05/qemu-cut-paste/
> >>>
> >>> OPEN QUESTIONS:
> >>>
> >>> - I'm not fully convinced that the `<source>` element is the right place for
> >>>    the new `clipboard` / `mouse` configuration options, but I'm not sure that
> >>>    adding a new xml element to the `<channel>` is the right approach either.
> >>>    Suggestions welcome.
> >>
> >> I am not convinced <channel> is appropriate either for -chardev
> >> qemu-vdagent. That's why in my dbus display series it's an
> >> implementation detail
> >> (https://patchew.org/Libvirt/20211222194345.766352-1-marcandre.lureau@redhat.com/20211222194345.766352-13-marcandre.lureau@redhat.com/),
> >> and it's not exposed to the domain XML directly. However I realize
> >> that my approach is probably broken, as it looks like I totally missed
> >> the associated virtserialport! :)
> >>
> >> As you say "source" is strange to put those extra channel options too.
> >>
> >> And the only really valid associated device is a virtserialport of
> >> name "com.redhat.spice.0", so what's the point in exposing that detail
> >> to the user?
>
> You could say the same thing about the normal spice vdagent, right? And
> we allow the user to specify a different virtio name for the spicevmc

Yes, although the spicevmc -chardev can is configurable via its name
to transport various content, whereas qemu-vdagent is limited to
spice-vdagent.

> channel. spice-vdagent does offer a --virtio-serial-port-path option
> that can be used to connect to a different name within the guest, after all.

Oh my, it's probably a good idea to deprecate it.

>
> >
> > At the QEMU level we have one serial port with chardv
> >
> >    -chardev qemu-vdagent,id=ch1,name=vdagent,clipboard=on
> >    -device virtio-serial-pci \
> >    -device virtserialport,chardev=ch1,id=ch1,name=com.redhat.spice.0
> >
> >
> > but IIUC, we can have multiple frontends - ie both VNC and DBus
> > display, and in that case the clipboard=on property on the
> > chardev will apply to both VNC & DBus displays. We can't
> > control clipboard independantly for the displays, so it is
> > right to put the control in the XML for the <channel> for
> > both VNC and DBus.
> >
>
> In addition to <channel>, there are several other xml elements that
> essentially map to a qemu character device: <serial>, <console>, etc.
> Would it make more sense to introduce a new element like this for the
> qemu-vdagent? This might make it easier to introduce new configuration
> options that wouldn't really fit in the general <channel>. For example,
> something like:
>
> <qemuvdagent>
>    <clipboard copypaste="yes"/>
>    <target type='virtio' name='com.redhat.spice.0'/>
> </qemuvdagent>
>
> Jonathon
>