Re: [gentoo-user] QEMU -nographic Option with OVMF

[Michael]

On Monday, 24 May 2021 02:01:15 BST Oliver Dixon wrote:
> Hi,
>
> I decided to bite the bullet yesterday and switch from clunky, and generally
> untoward, VirtualBox to QEMU/KVM for developing kernel modules. I have a
> working Gentoo VM with all the bells and whistles I need/want (UEFI
> booting, NIC passthrough, SSH forwarding, NFSv4 support, etc.), but it's
> running in an SDL window, which means the guest TTY will become confused
> and pretty much unusable whenever I change the window size. (Which is
> rather often since I use a tiling window manager.)

Have you tried '-display sdl,gl=on -vga virtio' and then use Ctrl+Alt+f to 
maximise it early in the boot process?  It seems to work OK here, without 
distorting the contents of the VM window.


> Since I'll only be using the TTY, the '-nographic' option to QEMU seems
> appropriate, but this causes the initial bootloader screen (OVMF/EDK-II) and
> GRUB to hang on stdout (screenshot attached). Here's my QEMU invocation
> script:
>
>         #!/bin/bash
>
>         exec qemu-system-x86_64 \
>                 -enable-kvm \
>                 -cpu host \
>                 -drive file=Gentoo-VM.img,if=virtio \
>                 -nic user,hostfwd=tcp:127.0.0.1:2222-:22 \
>                 -m 4G \
>                 -smp 12 \
>                 -name "Gentoo VM" \
>                 -bios /usr/share/edk2-ovmf/OVMF_CODE.fd \
>                 -nographic \
>                 $@
>
> I have to spawn another terminal to kill the QEMU process. I can make a bit
> of progress by telling the kernel to direct early messages to ttyS0, which
> does display the early bootup messages from Linux, but then hangs just
> before a login prompt would be shown (screenshot attached).
>
>         console=tty0 console=ttyS0,9600n8
>
> Again, I can't do anything other than a `pkill qemu` from elsewhere.
>
> Any ideas from someone more familiar with QEMU hosting Linux guests? I've
> only been using it for a day, most of which has been trying to fix this
> annoying behaviour.
>
> Cheers.

As far as I understand it (haven't tried it) you'll need to redirect the 
virtual console of the guest to the host.  Also configure GRUB to do the same.

For GRUB you'll probably need:

GRUB_TIMEOUT_STYLE=menu
GRUB_CMDLINE_LINUX="console=ttyS0"
GRUB_TERMINAL="console serial"

For the guest kernel command line you can append console=ttyS0.  Theoretically 
it should arrive at a login prompt on your terminal.

For testing kernels have a look here:

https://qemu-project.gitlab.io/qemu/system/linuxboot.html


To shut down the guest you could try using the QEMU monitor (Ctrl+Alt+2) and 
run 'system_powerdown', or Ctrl+Alt+3 for the serial port.