Failed to start ubuntu-cloud image directly from qemu

[HangShuYH]

Following https://github.com/virt-pvm/misc/blob/main/pvm-get-started-with-kata.md to start VM, the available userspace tools were too limited, so I decided to launch an Ubuntu cloud image using PVM.
I used the Ubuntu image from http://cloud-images-archive.ubuntu.com/releases/jammy/release-20250108/ubuntu-22.04-server-cloudimg-amd64-disk-kvm.img and extracted initrd.gz from it.
The QEMU I used was compiled from the pvm_qemu_migration branch at https://github.com/virt-pvm/qemu.
When I start the Guest Kernel with the following command, QEMU freezes without any output:

sudo ./qemu/build/qemu-bundle/usr/local/bin/qemu-system-x86_64 \
  --enable-kvm \
  -bios ./qemu/build/qemu-bundle/usr/local/share/qemu/qboot.rom \
  -m 6G \
  -kernel vmlinux.pvm_guest \
  -initrd ubuntu-initrd.gz \
  -nographic \
  -no-reboot \
  -append "root=/dev/vda1 rw pti=off nokaslr lapic=notscdeadline console=ttyS0" \
  -drive file=ubuntu.img,format=qcow2,if=virtio

Then I tried to erase -bios ./qemu/build/qemu-bundle/usr/local/share/qemu/qboot.rom, so that qemu use SeaBIOS by default. Then the pvm module warns Inject event in non-PVM mode.

Then I tried to use SeaBIOS with kvm_intel, everything is ok. So I guess the qboot startup might be incompatible with this image?

Could you provide some guidance on how to use qboot to launch an Ubuntu image, or how to start a VM with a comprehensive set of user programs?

[HangShuYH]

I'm pretty sure the issue is due to a qemu compatibility problem. When I used the qemu and qboot provided by kata (kata-runtime version: 3.19.1), the kernel booted normally.

[bysui]

Following https://github.com/virt-pvm/misc/blob/main/pvm-get-started-with-kata.md to start VM, the available userspace tools were too limited, so I decided to launch an Ubuntu cloud image using PVM. I used the Ubuntu image from http://cloud-images-archive.ubuntu.com/releases/jammy/release-20250108/ubuntu-22.04-server-cloudimg-amd64-disk-kvm.img and extracted initrd.gz from it. The QEMU I used was compiled from the pvm_qemu_migration branch at https://github.com/virt-pvm/qemu. When I start the Guest Kernel with the following command, QEMU freezes without any output:

sudo ./qemu/build/qemu-bundle/usr/local/bin/qemu-system-x86_64
--enable-kvm
-bios ./qemu/build/qemu-bundle/usr/local/share/qemu/qboot.rom
-m 6G
-kernel vmlinux.pvm_guest
-initrd ubuntu-initrd.gz
-nographic
-no-reboot
-append "root=/dev/vda1 rw pti=off nokaslr lapic=notscdeadline console=ttyS0"
-drive file=ubuntu.img,format=qcow2,if=virtio
Then I tried to erase -bios ./qemu/build/qemu-bundle/usr/local/share/qemu/qboot.rom, so that qemu use SeaBIOS by default. Then the pvm module warns Inject event in non-PVM mode.

Then I tried to use SeaBIOS with kvm_intel, everything is ok. So I guess the qboot startup might be incompatible with this image?

Could you provide some guidance on how to use qboot to launch an Ubuntu image, or how to start a VM with a comprehensive set of user programs?

Hi, @HangShuYH.

For now, PVM on QEMU only supports qboot instead of SeaBIOS, as SeaBIOS requires a page fault handler. However, PVM has a new PV event delivery ABI, and IDT-based event delivery is not supported. Therefore, if we try to support SeaBIOS, we would need to modify its source code, so we have chosen qboot as the default BIOS for QEMU.

I didn't encounter the problem. Are you using the latest code from the pvm_qemu_migration branch, which also changed when the pvm-6.12 branch was released? If so, you can try reverting the pvm-msr related commit, which is only useful for migration and doesn't affect normal operation. If you still encounter the problem, it may be that our QEMU branch is too far behind the upstream QEMU master. I'll try to sync the branch with upstream.

Thanks!