Black screen with Ubuntu guest in Windows host

[marco restelli]

Dear all,
   I have an Ubuntu virtual machine which works fine in a linux host
but gives a black screen in a Windows host. In Windows, I can switch
to a different TTY and log in to the text console, and I see the
system is up as expected and gdm3 is running. So it is only the TTY
with the login manager that is missing.

On Windows I use

qemu-system-x86_64.exe -m 4128 -smp 4 -vga virtio -accel
whpx,kernel-irqchip=off -drive file=ubuntu.qcow2

and -vga std gives the same result, i.e. black screen.

On Linux I use

qemu-system-x86_64 -m 4128 -smp 4 -vga virtio -accel kvm -cpu host
-drive file=ubuntu.qcow2

Both hosts use version

QEMU emulator version 6.2.0

Any idea how to solve/debug the problem?

Thanks,
   Marco