Re: Porting Xen in raspberry pi4B

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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 <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
> 
> 
>