On 05/04/2024 1:11 pm, Fouad Hilly wrote:
> Refactor and introduce --force option to xen-ucode, which skips microcode
> version check when updating x86 CPU micocode. A new hypercall introduced
> with flags field to facilitate the new option and allow for future flags
> as needed.
It's worth giving a bit of background for reviewers.
Basically, my "ucode=allow-same" for testing purposes has proved
insufficient, so we're wanting to replace it with a "user knows what
they're doing and gets to keep the pieces" option instead.
Upcoming is the Intel microcode-revision extension, which has different
implications for Xen than it does for Linux, by virtue of our
proto-support to re-scan CPUID and cope with new things appearing.
Also, while not a consideration for this issue, it subsequently turns
out that there is a microcode bug on Gemini Lake CPUs for which
downgrading the microcode is a viable and practical fix.
In all cases, having an ability to say "trust me, I know what I'm doing,
really try and give this blob to the CPU" would help in some corner cases.
~Andrew