Re: [PATCH v7 1/6] mm:/Kconfig changes for migrate on fault for device pages

Christoph Hellwig
2026-03-30T06:20:49Z

On Mon, Mar 30, 2026 at 07:30:12AM +0300, mpenttil@redhat.com wrote:
> From: Mika Penttilä <mpenttil@redhat.com>
>
> With the unified HMM/migrate_device page table walk
> migrate_device needs HMM enabled and HMM needs
> MMU notifiers. Enable them explicitly to avoid
> breaking random configs.

You can use a lot more space in your commit logs, ending the lines so
early reads a bit weird.

> diff --git a/mm/Kconfig b/mm/Kconfig
> index ebd8ea353687..583d92bba2e8 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -647,6 +647,7 @@ config MIGRATION
>
> config DEVICE_MIGRATION
> def_bool MIGRATION && ZONE_DEVICE
> + select HMM_MIRROR
>
> config ARCH_ENABLE_HUGEPAGE_MIGRATION
> bool
> @@ -1222,6 +1223,7 @@ config ZONE_DEVICE
> config HMM_MIRROR
> bool
> depends on MMU
> + select MMU_NOTIFIER

But either way this really should go into the patch that actually adds
the code dependency anyway.