Re: [PATCH v14 01/12] mm/Kconfig: changes for migrate on fault for device pages

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] mm/Kconfig: DEVICE_MIGRATION selects HMM_MIRROR without MMU dependency
--

commit 3e1dfa1b4fc87fd67c61777c9c5e43b8e801f019
Author: Mika Penttilä <mpenttil@redhat.com>

mm/Kconfig: changes for migrate on fault for device pages

This commit explicitly enables HMM for the unified HMM/migrate_device
page table walk in migrate_device, since HMM depends on MMU notifiers.

> diff --git a/mm/Kconfig b/mm/Kconfig
> index 604c58199acbf..b7a485beb9a78 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -687,6 +687,7 @@ config MIGRATION
>  
>  config DEVICE_MIGRATION
>  	def_bool MIGRATION && ZONE_DEVICE
> +	select HMM_MIRROR

[Severity: Low]
Does this regression violate Kconfig dependency rules by selecting HMM_MIRROR
without inheriting its dependencies?

In mm/Kconfig under DEVICE_MIGRATION, HMM_MIRROR is selected but its MMU
dependency is not included.

While currently unreachable because nothing currently selects DEVICE_MIGRATION,
if another config unconditionally uses select DEVICE_MIGRATION in the future,
it forces DEVICE_MIGRATION=y (bypassing the def_bool logic).

This would subsequently force HMM_MIRROR=y on non-MMU architectures, causing
unmet dependency warnings and potential build failures.

The Kconfig subsystem rules require that any config using select must explicitly
inherit the selected symbol's dependencies.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260922053421.4092027-1-mpenttil@redhat.com?part=1