Hi Stefano,

Thanks for the response!

I am following the same link you shared from the beginning. Tried the
command "vncviewer localhost:0" in DOM0 but same issue "Can't open
display", below are the logs:







*root@raspberrypi4-64:~# vncviewer localhost:0TigerVNC Viewer 64-bit
v1.11.0Built on: 2020-09-08 12:16Copyright (C) 1999-2020 TigerVNC Team and
many others (see README.rst)See https://www.tigervnc.org
<https://www.tigervnc.org> for information on TigerVNC.Can't open display:*

Below are the netstat logs, i couldn't see anything running at port 5900 or
5901:


























*root@raspberrypi4-64:~# netstat -tuwx Active Internet connections (w/o
servers)Proto Recv-Q Send-Q Local Address           Foreign Address
State       tcp        0    164 192.168.1.39:ssh        192.168.1.38:37472
<http://192.168.1.38:37472>      ESTABLISHED Active UNIX domain sockets
(w/o servers)Proto RefCnt Flags       Type       State         I-Node
Pathunix  8      [ ]         DGRAM      CONNECTED      10565 /dev/logunix
 3      [ ]         STREAM     CONNECTED      10891
/var/run/xenstored/socketunix  3      [ ]         STREAM     CONNECTED
 13791 unix  3      [ ]         STREAM     CONNECTED      10843
/var/run/xenstored/socketunix  3      [ ]         STREAM     CONNECTED
 10573 /var/run/xenstored/socketunix  2      [ ]         DGRAM
 CONNECTED      14510 unix  3      [ ]         STREAM     CONNECTED
 13249 unix  2      [ ]         DGRAM      CONNECTED      13887 unix  2
 [ ]         DGRAM      CONNECTED      10599 unix  3      [ ]
STREAM     CONNECTED      14005 unix  3      [ ]         STREAM
CONNECTED      13258 unix  3      [ ]         STREAM     CONNECTED
 13248 unix  3      [ ]         STREAM     CONNECTED      14003 unix  3
 [ ]         STREAM     CONNECTED      10572 /var/run/xenstored/socketunix
 3      [ ]         STREAM     CONNECTED      10786
/var/run/xenstored/socketunix  3      [ ]         DGRAM      CONNECTED
 13186 unix  3      [ ]         STREAM     CONNECTED      10864
/var/run/xenstored/socketunix  3      [ ]         STREAM     CONNECTED
 10812 /var/run/xenstored/socketunix  2      [ ]         DGRAM
 CONNECTED      14083 unix  3      [ ]         STREAM     CONNECTED
 10813 /var/run/xenstored/socket*









*unix  3      [ ]         STREAM     CONNECTED      14068 unix  3      [ ]
        STREAM     CONNECTED      13256 unix  3      [ ]         STREAM
CONNECTED      10571 /var/run/xenstored/socketunix  3      [ ]
STREAM     CONNECTED      10842 unix  3      [ ]         STREAM
CONNECTED      13985 unix  3      [ ]         DGRAM      CONNECTED
 13185 unix  2      [ ]         STREAM     CONNECTED      13884 unix  2
 [ ]         DGRAM      CONNECTED      14528 unix  2      [ ]         DGRAM
     CONNECTED      13785 unix  3      [ ]         STREAM     CONNECTED
 14034 *

Attaching xen log files of /var/log/xen.
I didn't get the role of QEMU here because as mentioned earlier, I am
porting in raspberrypi 4B.

Regards,
Vipul Kumar

On Wed, Oct 19, 2022 at 12:43 AM Stefano Stabellini <sstabell...@kernel.org>
wrote:

> It usually works the way it is described in the guide:
>
>
> https://www.virtuatopia.com/index.php?title=Configuring_a_VNC_based_Graphical_Console_for_a_Xen_Paravirtualized_domainU_Guest
>
> You don't need to install any VNC-related server software because it is
> already provided by Xen (to be precise it is provided by QEMU working
> together with Xen.)
>
> You only need the vnc client in dom0 so that you can connect, but you
> could also run the vnc client outside from another host. So basically
> the following should work when executed in Dom0 after creating DomU:
>
>   vncviewer localhost:0
>
> Can you attach the Xen and QEMU logs (/var/log/xen/*)? And also use
> netstat -taunp to check if there is anything running at port 5900 or
> 5901?
>
> Cheers,
>
> Stefano
>
>
> On Tue, 18 Oct 2022, Vipul Suneja wrote:
> > Hi Stefano,
> >
> > Thanks for the response!
> >
> > I could install tigerVNC, x11vnc & libvncserver in Dom0
> xen-image-minimal but only manage to install libvncserver(couldn't install
> tigervnc
> > & x11vnc because of x11
> > support missing, it's wayland) in DOMU custom graphical image. I tried
> running vncviewer with IP address & port in dom0 to access the domu
> > graphical image display as per below commands.
> >
> >  vncviewer 192.168.1.42:5901
> >
> >  But it showing can't open display, below are the logs:
> >
> > root@raspberrypi4-64:~/guest1# vncviewer 192.168.1.42:5901
> >
> > TigerVNC Viewer 64-bit v1.11.0
> > Built on: 2020-09-08 12:16
> > Copyright (C) 1999-2020 TigerVNC Team and many others (see README.rst)
> > See https://www.tigervnc.org for information on TigerVNC.
> > Can't open display:
> > root@raspberrypi4-64:~/guest1#
> >
> > I am not exactly sure what the issue is but I thought only libvncserver
> in DOMU could work to get access but it did not work.
> > If TigerVNC is the issue here then is there any other VNC source which
> could be installed for both x11 & wayland supported images?
> >
> > Regards,
> > Vipul Kumar
> >
> > On Tue, Oct 18, 2022 at 2:40 AM Stefano Stabellini <
> sstabell...@kernel.org> wrote:
> >       VNC is typically easier to setup, because SDL needs extra
> libraries at
> >       build time and runtime. If QEMU is built without SDL support it
> won't
> >       start when you ask for SDL.
> >
> >       VNC should work with both x11 and wayland in your domU. It doesn't
> work
> >       at the x11 level, it exposes a special fbdev device in your domU
> that
> >       should work with:
> >       - a graphical console in Linux domU
> >       - x11
> >       - wayland (but I haven't tested this so I am not 100% sure about
> it)
> >
> >       When you say "it doesn't work", what do you mean? Do you get a
> black
> >       window?
> >
> >       You need CONFIG_XEN_FBDEV_FRONTEND in Linux domU
> >       (drivers/video/fbdev/xen-fbfront.c). I would try to get a
> graphical text
> >       console up and running in your domU before attempting x11/wayland.
> >
> >       Cheers,
> >
> >       Stefano
> >
> >       On Mon, 17 Oct 2022, Vipul Suneja wrote:
> >       > Hi,
> >       > Thanks!
> >       >
> >       > I have ported xen minimal image as DOM0 & custom wayland GUI
> based image as DOMU in raspberry pi4B. I am trying to make GUI
> >       display up
> >       > for guest machine. I tried using sdl, included below line in
> guest.conf file
> >       > vfb= [ 'sdl=1' ]
> >       >
> >       > But it is throwing below error:
> >       >
> >       > root@raspberrypi4-64:~/guest1# xl create -c guest1.cfg
> >       > Parsing config from guest1.cfg
> >       > libxl: error: libxl_qmp.c:1400:qmp_ev_fd_callback: Domain
> 3:error on QMP socket: Connection reset by peer
> >       > libxl: error: libxl_qmp.c:1439:qmp_ev_fd_callback: Domain
> 3:Error happened with the QMP connection to QEMU
> >       > libxl: error: libxl_dm.c:3351:device_model_postconfig_done:
> Domain 3:Post DM startup configs failed, rc=-26
> >       > libxl: error: libxl_create.c:1867:domcreate_devmodel_started:
> Domain 3:device model did not start: -26
> >       > libxl: error: libxl_aoutils.c:646:libxl__kill_xs_path: Device
> Model already exited
> >       > libxl: error: libxl_domain.c:1183:libxl__destroy_domid: Domain
> 3:Non-existant domain
> >       > libxl: error: libxl_domain.c:1137:domain_destroy_callback:
> Domain 3:Unable to destroy guest
> >       > libxl: error: libxl_domain.c:1064:domain_destroy_cb: Domain
> 3:Destruction of domain failed
> >       >
> >       > Another way is VNC, i could install tigervnc in DOM0 but same i
> couldn't in guest machine because it doesn't support
> >       x11(supports wayland
> >       > only). I am completely blocked here, Need your support to enable
> the display up.
> >       > Any alternative of VNC which could work in both x11 & wayland
> supported images?
> >       >
> >       > Any input on VNC, SDL or any other way to proceed on this?
> Looking forward to hearing from you.
> >       >
> >       > Regards,
> >       > Vipul Kumar
> >
> >
> >

Attachment: qemu-dm-guest1.log
Description: Binary data

Attachment: xl-guest1.log
Description: Binary data

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