[RFC PATCH 2/6] drm/gpusvm: Update GPU SVM / Xe to twopass MMU notifier

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

From: Matthew Brost <matthew.brost@intel.com>

Update GPU SVM and Xe to use two-pass MMU notifiers, enabling pipelined
TLB invalidations across VMs or multiple devices.

The driver-side (Xe) implementation is not yet implemented.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/drm_gpusvm.c | 18 +++++++++++-------
 drivers/gpu/drm/xe/xe_svm.c  |  9 +++++----
 include/drm/drm_gpusvm.h     | 11 +++++++----
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index 661306da6b2d..92dc7d2bd6cf 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -374,10 +374,13 @@ notifier_iter_first(struct rb_root_cached *root, unsigned long start,
 	     (notifier__) = (next__), (next__) = __drm_gpusvm_notifier_next(notifier__))
 
 /**
- * drm_gpusvm_notifier_invalidate() - Invalidate a GPU SVM notifier.
+ * drm_gpusvm_notifier_invalidate_twopass() - Invalidate a GPU SVM notifie,
+ * fist pass.
+ *
  * @mni: Pointer to the mmu_interval_notifier structure.
  * @mmu_range: Pointer to the mmu_notifier_range structure.
  * @cur_seq: Current sequence number.
+ * @pass: First pass of MMU notifier
  *
  * This function serves as a generic MMU notifier for GPU SVM. It sets the MMU
  * notifier sequence number and calls the driver invalidate vfunc under
@@ -386,9 +389,10 @@ notifier_iter_first(struct rb_root_cached *root, unsigned long start,
  * Return: true if the operation succeeds, false otherwise.
  */
 static bool
-drm_gpusvm_notifier_invalidate(struct mmu_interval_notifier *mni,
-			       const struct mmu_notifier_range *mmu_range,
-			       unsigned long cur_seq)
+drm_gpusvm_notifier_invalidate_twopass(struct mmu_interval_notifier *mni,
+				       const struct mmu_notifier_range *mmu_range,
+				       unsigned long cur_seq,
+				       struct mmu_interval_notifier_pass **pass)
 {
 	struct drm_gpusvm_notifier *notifier =
 		container_of(mni, typeof(*notifier), notifier);
@@ -399,7 +403,7 @@ drm_gpusvm_notifier_invalidate(struct mmu_interval_notifier *mni,
 
 	down_write(&gpusvm->notifier_lock);
 	mmu_interval_set_seq(mni, cur_seq);
-	gpusvm->ops->invalidate(gpusvm, notifier, mmu_range);
+	gpusvm->ops->invalidate_twopass(gpusvm, notifier, mmu_range, pass);
 	up_write(&gpusvm->notifier_lock);
 
 	return true;
@@ -409,7 +413,7 @@ drm_gpusvm_notifier_invalidate(struct mmu_interval_notifier *mni,
  * drm_gpusvm_notifier_ops - MMU interval notifier operations for GPU SVM
  */
 static const struct mmu_interval_notifier_ops drm_gpusvm_notifier_ops = {
-	.invalidate = drm_gpusvm_notifier_invalidate,
+	.invalidate_twopass = drm_gpusvm_notifier_invalidate_twopass,
 };
 
 /**
@@ -440,7 +444,7 @@ int drm_gpusvm_init(struct drm_gpusvm *gpusvm,
 		    const struct drm_gpusvm_ops *ops,
 		    const unsigned long *chunk_sizes, int num_chunks)
 {
-	if (!ops->invalidate || !num_chunks)
+	if (!ops->invalidate_twopass || !num_chunks)
 		return -EINVAL;
 
 	gpusvm->name = name;
diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
index e35c6d4def20..23c5b363261c 100644
--- a/drivers/gpu/drm/xe/xe_svm.c
+++ b/drivers/gpu/drm/xe/xe_svm.c
@@ -171,9 +171,10 @@ xe_svm_range_notifier_event_end(struct xe_vm *vm, struct drm_gpusvm_range *r,
 						   mmu_range);
 }
 
-static void xe_svm_invalidate(struct drm_gpusvm *gpusvm,
-			      struct drm_gpusvm_notifier *notifier,
-			      const struct mmu_notifier_range *mmu_range)
+static void xe_svm_invalidate_twopass(struct drm_gpusvm *gpusvm,
+				      struct drm_gpusvm_notifier *notifier,
+				      const struct mmu_notifier_range *mmu_range,
+				      struct mmu_interval_notifier_pass **p)
 {
 	struct xe_vm *vm = gpusvm_to_vm(gpusvm);
 	struct xe_device *xe = vm->xe;
@@ -553,7 +554,7 @@ static const struct drm_pagemap_devmem_ops dpagemap_devmem_ops = {
 static const struct drm_gpusvm_ops gpusvm_ops = {
 	.range_alloc = xe_svm_range_alloc,
 	.range_free = xe_svm_range_free,
-	.invalidate = xe_svm_invalidate,
+	.invalidate_twopass = xe_svm_invalidate_twopass,
 };
 
 static const unsigned long fault_chunk_sizes[] = {
diff --git a/include/drm/drm_gpusvm.h b/include/drm/drm_gpusvm.h
index 8d613e9b2690..8b5e159857fc 100644
--- a/include/drm/drm_gpusvm.h
+++ b/include/drm/drm_gpusvm.h
@@ -63,17 +63,20 @@ struct drm_gpusvm_ops {
 	void (*range_free)(struct drm_gpusvm_range *range);
 
 	/**
-	 * @invalidate: Invalidate GPU SVM notifier (required)
+	 * @invalidate_twopass: Invalidate first pass GPU SVM notifier (required)
 	 * @gpusvm: Pointer to the GPU SVM
 	 * @notifier: Pointer to the GPU SVM notifier
 	 * @mmu_range: Pointer to the mmu_notifier_range structure
+	 * @pass: Pass of MMU notifier, optionally populated driver side
+	 * if a second pass of MMU notifier is desired
 	 *
 	 * Invalidate the GPU page tables. It can safely walk the notifier range
 	 * RB tree/list in this function. Called while holding the notifier lock.
 	 */
-	void (*invalidate)(struct drm_gpusvm *gpusvm,
-			   struct drm_gpusvm_notifier *notifier,
-			   const struct mmu_notifier_range *mmu_range);
+	void (*invalidate_twopass)(struct drm_gpusvm *gpusvm,
+				   struct drm_gpusvm_notifier *notifier,
+				   const struct mmu_notifier_range *mmu_range,
+				   struct mmu_interval_notifier_pass **pass);
 };
 
 /**
-- 
2.50.1