Update: The original post is from November 2024. I updated the post in the meantime a couple of times to reflect my latest knowledge. During my work as virtualization engineer at Cyberus Technology, I work from time to time with libvirt. Specifically, I am working with live-migration of QEMU/KVM VMs Read more…
Update: Since Cloud Hypervisor release v38, you can also run a Linux with this driver in Cloud Hypervisor and see the output. In earlier blog posts, I discussed QEMU’s debugcon device and presented a minimal driver for it written in x86 assembly. In this blog post, we go a little Read more…
This is an educational resource I wish I had when I started digging into low-level and operating systems during my early time of my studies at the university. However, dear past me, I got your back! Do you want to see a minimal way to communicate with (virtual) hardware and Read more…
In the previous blog post we talked about how to use QEMUs debugcon feature. To do this responsibly, we should only do this if the binary runs in fact inside QEMU. To find this out, one can use the cpuid instruction. It gives us a lot of information about our Read more…
Update 2024-01-30: The same underlying mechanism was just merged in Cloud Hypervisor as well! It is exposed as –debug-console <target>. This article mostly applies to Cloud Hypervisor as well. Problem: Getting Early Debug Output as Kernel Developer QEMU is a VMM often used for low-level OS/kernel development and testing. When Read more…