U-Boot has a new continuous integration (CI) lab page that provides a real-time look at the status of various development boards. The page, located at https://lab.u-boot.org/, offers a simple and clean interface that allows developers and curious people to quickly check on the health and activity of each board in the lab.

When you first visit the page, you’ll see a grid of all the available boards. Each board’s card displays its name and current status, making it easy to see which boards are online and which are not. A single click on any board will show a console view, taken from the last health check. This allows you see why boards are failing, for example.

This new lab page is a nice resource for the U-Boot community. It provides a transparent and accessible way to monitor this part of the CI system.

Check it out and get in touch if you have any suggestions or feedback! 🧪

In the world of software development, consistency is key. A recent update to U-Boot Concept takes a solid step in that direction by restructuring how it handles emulation targets. This change makes life easier for developers working across different processor architectures.

Previously there were inconsistencies in the configuration system (Kconfig). For example, enabling QEMU emulation for ARM systems used the ARCH_QEMU symbol, while x86 systems used VENDOR_EMULATION for a similar purpose. This could create confusion and added complexity when managing board configurations.

To resolve this, a new, architecture-neutral symbol, MACH_QEMU, has been introduced. This single, unified option replaces the separate symbols for both ARM and x86 emulation targets.

This small but important merge tidies up the codebase, creating a more consistent and intuitive developer experience. It also sets the stage for future work, with the potential to extend this unified approach to other architectures. It’s a great example of the continuous effort to keep U-Boot clean, efficient, and easy to maintain for everyone involved.

A few weeks ago I took a look at Qboot, a minimal x86 firmware for QEMU which can boot in milliseconds. Qboot was written by Paolo Bonzini and dates from 2015 and there is an LWN article with the original announcement.

I tried it on my machine and it booted in QEMU (with kvm) in about 20ms, from entering Qboot to entering Linux. Very impressive! I was intrigued as to what makes it so fast.

There is another repo, qemu-boot-time by Stefan Garzarella, which provides an easy means to benchmark the boot. It uses perf events in Linux to detect the start and end of Qboot.

Using x86 post codes, I added the same to U-Boot. Initially the boot time was 2.9 seconds! Terrible. Here is a script which works on my machine and measures the time taken for U-Boot boot, using the qemu-x86_64 target:

It turned out that almost two of the seconds were the U-Boot boot delay. Another 800ms was the PXE menu delay. With those removed the time dropped to 210ms, which is not bad.

Using CONFIG_NO_NET dropping CONFIG_VIDEO each shaved off about 50ms. I then tried passing the kernel and initrd through QEMU using the QFW interface. It only saved 15ms but it is something.

I figured that command-line processing would be quite slow. With CONFIG_CMDLINE disabled another 5ms was saved. A final 7ms came from disabling filesystems and EFI loader. Small gains.

In the end, my result is about 83ms (in bold below):

$ ./contrib/qemu-boot-timer.sh
starting perf
building U-Boot
running U-Boot in QEMU
waiting for a bit
qemu-system-x86_64: terminating on signal 15 from pid 2775874 (bash)
parsing perf results
1) pid 2779434
qemu_init_end: 51.924873
u_boot_start: 51.962744 (+0.037871)
u_boot_do_boot: 134.781048 (+82.818304)

One final note: the qemu-x86_64 target actually boots by starting SPL in 16-bit mode and then moving to 64-bit mode to start U-Boot proper. This was partly to avoid calling 16-bit video ROMs from 64-bit code. Now that bochs is used for the display, it should be easy enough to drop SPL for this target. I’m not sure how much time that would save.

Note: Some final hacks are tagged here.