Re: Porting Xen in raspberry pi4B

[Vipul Suneja <vsuneja63@xxxxxxxxx>]

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 <sstabellini@xxxxxxxxxx> 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