drm/amdkfd: deregister svm range

When application explicitly call unmap or unmap from mmput when
application exit, driver will receive MMU_NOTIFY_UNMAP event to remove
svm range from process svms object tree and list first, unmap from GPUs
(in the following patch).

Split the svm ranges to handle partial unmapping of svm ranges. To
avoid deadlocks, updating MMU notifiers, range lists and interval trees
is done in a deferred worker. New child ranges are attached to their
parent range's child_list until the worker can update the
svm_range_list. svm_range_set_attr flushes deferred work and takes the
mmap_write_lock to guarantee that it has an up-to-date svm_range_list.
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_priv.h

@@ -735,6 +735,9 @@ struct svm_range_list {
 	struct mutex			lock;
 	struct rb_root_cached		objects;
 	struct list_head		list;
+	struct work_struct		deferred_list_work;
+	struct list_head		deferred_range_list;
+	spinlock_t			deferred_list_lock;
 };
 
 /* Process data */

drivers/gpu/drm/amd/amdkfd/kfd_svm.h

@@ -33,6 +33,18 @@
 #include "amdgpu.h"
 #include "kfd_priv.h"
 
+enum svm_work_list_ops {
+	SVM_OP_NULL,
+	SVM_OP_UNMAP_RANGE,
+	SVM_OP_UPDATE_RANGE_NOTIFIER,
+	SVM_OP_ADD_RANGE
+};
+
+struct svm_work_list_item {
+	enum svm_work_list_ops op;
+	struct mm_struct *mm;
+};
+
 /**
  * struct svm_range - shared virtual memory range
  *
@@ -54,6 +66,9 @@
  * @actual_loc: the actual location, 0 for CPU, or GPU id
  * @granularity:migration granularity, log2 num pages
  * @notifier:   register mmu interval notifier
+ * @work_item:  deferred work item information
+ * @deferred_list: list header used to add range to deferred list
+ * @child_list: list header for split ranges which are not added to svms yet
  * @bitmap_access: index bitmap of GPUs which can access the range
  * @bitmap_aip: index bitmap of GPUs which can access the range in place
  *
@@ -79,6 +94,9 @@ struct svm_range {
 	uint32_t			actual_loc;
 	uint8_t				granularity;
 	struct mmu_interval_notifier	notifier;
+	struct svm_work_list_item	work_item;
+	struct list_head		deferred_list;
+	struct list_head		child_list;
 	DECLARE_BITMAP(bitmap_access, MAX_GPU_INSTANCE);
 	DECLARE_BITMAP(bitmap_aip, MAX_GPU_INSTANCE);
 };