Re: xen-bootable DomU images for linux

[Chuck Zmudzinski <frchuckz%gmail.com@localhost>]

On 1/10/2023 6:52 PM, Brook Milligan wrote:
> > On Jan 10, 2023, at 1:16 PM, Chuck Zmudzinski <frchuckz%gmail.com@localhost> wrote:
> > 
> > I think vfb is only for PV guests, so try commenting out that line.
> > 
> > For hvm, I recommend setting:
> > vga = 'stdvga'
> > videoram = '16'
> > 
> > The default vga is cirrus, but I think it can only have 4 MB videoram.
> > With 16 MB videoram, you can do 1920x1080 resolution.
>
> Thanks to all the help, I’ve gotten most of this to work for both Debian and LinuxMint; I’ll  summarize once complete for the record.
>
> What has worked: booting install images, connecting via vnc, installing the OS on a second disk image, booting the second image.  For Debian, all this works, and the second disk can be run as a PVH DomU.  For LinuxMint, all this works for HVM DomUs only.
>
> I have tried more or less the same configuration for the LinuxMint PV DomU as for the working Debian PV DomU:
>
> kernel='/xen/linuxmint-21.1-cinnamon-64bit-vmlinuz-5.15.0-56-generic'
> ramdisk='/xen/linuxmint-21.1-cinnamon-64bit-initrd.img-5.15.0-56-generic'
> type='pvh'
> memory = 2048
> cpu_weight = 64
> name = "linuxmint-pv"
> vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
> disk = [ 'file:/xen/linuxmint-21.1-cinnamon-64bit.img,ioemu:hda,w', ]
> root = "/dev/xvda1"
> vga = 'stdvga'
> videoram = '16'
> vfb = [ 'type=vnc,vnclisten=127.0.0.1’ ]
>
> This reports in the vnc window “This VM has no graphic display device.”  That message occurs with or without the vga+videoram statements and with or without the vfb statement.
>
> Any ideas?

I am fairly sure the vga and videoram settings don't apply with pv or pvh, they are qemu
options which is only used in hvm guests so you can comment those out in pv/pvh mode.
The pv and pvh guests use the Xen vfb device.

The difference might be that the LinuxMint kernel might not have support for the
paravirtualized vfb device.

Linux distros usually have a /boot/config-<kernel version> file that shows the compiled
options for the kernel the distro is using. Boot as hvm or try to connect to the console in
pv/pvh  mode and look in that file for the

CONFIG_XEN_FBDEV_FRONTEND=y

It could be =m also, but if it is

# CONFIG_XEN_FBDEV_FRONTEND is not set

you need to see if LinuxMint provides a kernel with that option
or try to compile a LinuxMint kernel with that option yourself.

I can't think of any other reason why it isn't working on LinuxMint.

For the linux kernel command line of a pv or pvh linux guest, I have
'xen-fbfront.video=24,1368,768' as one of the kernel command line
options to set the color depth and resolution of the display for
the guest. I don't think it is necessary to set in on the command line
but it is one way to set the resolution with the vfb video device.

All the best,

Chuck
 
>
> Thanks again for all the help.
>
> Cheers,
> Brook
>