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Re: [PATCH v2 2/2] x86/ucode: Add Kconfig option to remove microcode loading
- To: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
- Date: Mon, 12 Jan 2026 20:12:59 +0100
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- Cc: Doug Goldstein <cardoe@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, "Michal Orzel" <michal.orzel@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>, Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 12 Jan 2026 19:13:27 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi,
On Mon Jan 12, 2026 at 7:47 PM CET, Alejandro Vallejo wrote:
> On Mon Jan 12, 2026 at 6:15 PM CET, Andrew Cooper wrote:
>> On 12/01/2026 3:02 pm, Alejandro Vallejo wrote:
>>> automation/gitlab-ci/build.yaml | 2 +-
>>> docs/misc/efi.pandoc | 2 ++
>>> docs/misc/xen-command-line.pandoc | 4 ++--
>>> xen/arch/x86/Kconfig | 14 +++++++++++++-
>>> xen/arch/x86/cpu/microcode/amd.c | 22 +++++++++++++---------
>>> xen/arch/x86/cpu/microcode/core.c | 25 ++++++++++++++++++-------
>>> xen/arch/x86/cpu/microcode/intel.c | 16 +++++++++-------
>>> xen/arch/x86/efi/efi-boot.h | 3 ++-
>>> xen/arch/x86/platform_hypercall.c | 2 ++
>>> xen/common/Makefile | 3 ++-
>>> 10 files changed, 64 insertions(+), 29 deletions(-)
>>
>> Much nicer in terms of (non) invasiveness.
An interesting fact came to my attention. If you set a function pointer as
IS_ENABLED(x) ? foo : NULL, rather than ifdeffing out the compiler doesn't even
need __maybe_unused to eliminate the statics.
I'm adjusting as needed and creating something so that...
custom_param_if("ucode", parse_ucode, IS_ENABLED(CONFIG_MICROCODE_LOADING));
... does the right thing. I'm sure it'll have uses outside this (minor) patch to
remove a number of cmdline handlers when the feature they control isn't active.
Cheers,
Alejandro
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