On Fri, Jan 18, 2019 at 05:18:12PM +0100, Arnd Bergmann wrote:

The migrate_pages system call has an assigned number on all architectures
except ARM. When it got added initially in commit d80ade7b3231 ("ARM:
Fix warning: #warning syscall migrate_pages not implemented"), it was
intentionally left out based on the observation that there are no 32-bit
ARM NUMA systems.

However, there are now arm64 NUMA machines that can in theory run 32-bit
kernels (actually enabling NUMA there would require additional work)
as well as 32-bit user space on 64-bit kernels, so that argument is no
longer very strong.

Assigning the number lets us use the system call on 64-bit kernels as well
as providing a more consistent set of syscalls across architectures.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

For the arm64 part:

Acked-by: Catalin Marinas <catalin.marinas@arm.com>