Add a per-process MMU notifier lock for processing notifiers from
userptrs. Use that lock to properly synchronize page table updates with
MMU notifiers.
Signed-off-by: NFelix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Xiaogang Chen<Xiaogang.Chen@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>