On Mon, Dec 01, 2025 at 06:54:11PM +0000, David Matlack wrote: > To handle pci=assign-busses, perhaps something like this? Are there any > other places where the kernel could change busses?
In theory the algorithm to assign bus numbers could change from one kernel version to the next. Ilpo (+cc) is currently reworking the resource allocation algorithm. That work primarily covers MMIO window sizing, but bus numbers are resources as well and could be affected by changes. Resource allocation code is already quite convoluted and sprinkling liveupdate special cases all over it may not be received with enthusiasm. ;) Of course in practice, changes to the algorithm do not happen often and the kernel will preserve bus numbers as set by BIOS. Only if it detects incorrect bus assignments or if forced via the command line will the kernel re-assign bus numbers. But you do gain a bit of reliability if you don't assume bus numbers to stay the same and instead use the "path from root" approach to identify devices. Thanks, Lukas
