Re: Porting Xen in raspberry pi4B

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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