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

[Christoph Hellwig <hch@infradead.org>]

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.