Re: [PATCH 0/4] Add Kconfig option to remove microcode loading support

[Jan Beulich <jbeulich@suse.com>]

On 12.11.2025 17:22, Alejandro Vallejo wrote:
> Hi,
> 
> The series is mostly a refactor between everything needed to load microcode and
> the bare minimum to probe the current microcode revision.
> 
> The Kconfig option keeps the reading of microcode rev data around, as it's very
> relevant for security and debuggability in order to deduce which erratas apply
> to the current platform.
> 
> The idea is to move everything that must still be compiled with !CONFIG_UCODE
> onto {,amd-,intel-}base.c, then remove everything else conditionally at the
> Makefile level.
> 
> Renaming files (e.g: s/base/core/ and s/core/common/) would better reflect
> post-series reality, but it'd be annoying for later backports in this general
> area.
> 
> Cheers,
> Alejandro
> 
> Alejandro Vallejo (4):
>   x86: Split out AMD-specific code to be executed without ucode loading
>   x86: Split out Intel-specific code to be executed without ucode
>     loading
>   x86: Split out early_microcode_load() and microcode_load_one()
>   x86: Add Kconfig option to disable microcode loading
> 
>  xen/arch/x86/Kconfig                    | 12 ++++
>  xen/arch/x86/cpu/microcode/Makefile     |  9 ++-
>  xen/arch/x86/cpu/microcode/amd-base.c   | 55 +++++++++++++++++++
>  xen/arch/x86/cpu/microcode/amd.c        | 55 ++-----------------
>  xen/arch/x86/cpu/microcode/amd.h        | 15 +++++
>  xen/arch/x86/cpu/microcode/base.c       | 73 +++++++++++++++++++++++++
>  xen/arch/x86/cpu/microcode/core.c       | 58 +-------------------
>  xen/arch/x86/cpu/microcode/intel-base.c | 50 +++++++++++++++++
>  xen/arch/x86/cpu/microcode/intel.c      | 56 +++----------------
>  xen/arch/x86/cpu/microcode/intel.h      | 16 ++++++
>  xen/arch/x86/cpu/microcode/private.h    | 14 +++++
>  xen/arch/x86/efi/efi-boot.h             |  2 +-
>  xen/arch/x86/platform_hypercall.c       |  2 +
>  13 files changed, 259 insertions(+), 158 deletions(-)
>  create mode 100644 xen/arch/x86/cpu/microcode/amd-base.c
>  create mode 100644 xen/arch/x86/cpu/microcode/amd.h
>  create mode 100644 xen/arch/x86/cpu/microcode/base.c
>  create mode 100644 xen/arch/x86/cpu/microcode/intel-base.c
>  create mode 100644 xen/arch/x86/cpu/microcode/intel.h

Purely based on this diffstat: A doc update likely is necessary as well, as
the ucode= command line option now becomes only conditionally applicable (aiui,
i.e. without having looked at the patches them selves).

Jan