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.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Mika Penttilä <mpenttil@redhat.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

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
 
 config GET_FREE_REGION
 	bool
-- 
2.50.0

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.