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

[Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>]

On Thu Nov 13, 2025 at 8:36 AM CET, Jan Beulich wrote:
> 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

Yes, that sounds sensible.

Cheers,
Alejandro