Since 2018 U-Boot has had a good selection of features for running on top of QEMU, including: Most of this was written by Bin Meng. It uses driver model and is nicely implemented. What’s new? More recently a few more features have been added: The `virtio list` command can be useful for seeing what paravirtualised…
What is virtio-fs? For those unfamiliar, virtio-fs is a modern shared filesystem designed specifically for virtualised environments. It allows a virtual machine (the “guest”) to access a directory on the host system, but it does so with a focus on performance and providing local filesystem semantics. Unlike traditional methods like network filesystems (e.g., NFS, Samba)…
U-Boot makes extensive use of linker-generated lists to discover everything from drivers to commands at runtime. This clever mechanism allows developers to add new features with a single macro, and the linker automatically assembles them into a contiguous array. The C code can then iterate through this array by finding its start and end markers,…
U-Boot supports a fairly wide variety of filesystems, including ext4, ubifs, fat, exfat, zfs, btrfs. These are an important part of bootloader functionality, since reading files from bare partitions or disk offsets is neither scalable nor convenient. The filesystem API is functional but could use an overhaul. The main interface is in fs/fs.c, which looks…
VBE has been a long-running project to create a smaller and faster alternative to EFI. It was originally introduced as a concept in 2022, along with a sandbox implementation and a simple firmware updater for fwupd. In the intervening period an enormous about of effort has gone into getting this landed in U-Boot for a…
