AMD CPU Microcode Will Be Getting Larger With Future Processors

Future AMD CPUs will be having larger microcode patches and thus the Linux kernel is now being adapted to better handle that increased microcode payload.

Right now the Linux kernel has a maximum microcode patch size for AMD CPUs that is three times the kernel's page size (typically 4K). But with a patch published yesterday that will "increase substantially" to eight times the page size. The increase is intentionally quite a magnitude larger in order to avoid future patches further having to bump the patch size limit in later generations.

It's not noted what these "future CPUs" are with the larger microcode requirements, but given the timing is presumably for Zen 5. There's recently been various AMD Family 26 patches likely as Zen 5 appearing for different Linux changes in preparing the kernel for these next-generation client and server processors. It's also not elaborated on why the CPU microcode size will be increasing.

Existing AMD Zen 4 CPUs.

In any event the simple patch to bump the AMD CPU microcode limit is now out for review. It's also marked for back-porting to existing stable kernel versions.