[PATCH v6 4/8] drm/gpusvm: refactor core API to use pages struct

[Matthew Auld <matthew.auld@intel.com>]

Refactor the core API of get/unmap/free pages to all operate on
drm_gpusvm_pages. In the next patch we want to export a simplified core
API without needing fully blown svm range etc.

Suggested-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/drm_gpusvm.c | 161 ++++++++++++++++++++++++-----------
 1 file changed, 110 insertions(+), 51 deletions(-)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index fa193dd265b0..eb50ed0d0f55 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -980,19 +980,18 @@ drm_gpusvm_range_find_or_insert(struct drm_gpusvm *gpusvm,
 EXPORT_SYMBOL_GPL(drm_gpusvm_range_find_or_insert);
 
 /**
- * __drm_gpusvm_range_unmap_pages() - Unmap pages associated with a GPU SVM range (internal)
+ * __drm_gpusvm_unmap_pages() - Unmap pages associated with GPU SVM pages (internal)
  * @gpusvm: Pointer to the GPU SVM structure
- * @range: Pointer to the GPU SVM range structure
+ * @svm_pages: Pointer to the GPU SVM pages structure
  * @npages: Number of pages to unmap
  *
- * This function unmap pages associated with a GPU SVM range. Assumes and
+ * This function unmap pages associated with a GPU SVM pages struct. Assumes and
  * asserts correct locking is in place when called.
  */
-static void __drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
-					   struct drm_gpusvm_range *range,
-					   unsigned long npages)
+static void __drm_gpusvm_unmap_pages(struct drm_gpusvm *gpusvm,
+				     struct drm_gpusvm_pages *svm_pages,
+				     unsigned long npages)
 {
-	struct drm_gpusvm_pages *svm_pages = &range->pages;
 	struct drm_pagemap *dpagemap = svm_pages->dpagemap;
 	struct device *dev = gpusvm->drm->dev;
 	unsigned long i, j;
@@ -1028,17 +1027,15 @@ static void __drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
 }
 
 /**
- * drm_gpusvm_range_free_pages() - Free pages associated with a GPU SVM range
+ * __drm_gpusvm_free_pages() - Free dma array associated with GPU SVM pages
  * @gpusvm: Pointer to the GPU SVM structure
- * @range: Pointer to the GPU SVM range structure
+ * @svm_pages: Pointer to the GPU SVM pages structure
  *
  * This function frees the dma address array associated with a GPU SVM range.
  */
-static void drm_gpusvm_range_free_pages(struct drm_gpusvm *gpusvm,
-					struct drm_gpusvm_range *range)
+static void __drm_gpusvm_free_pages(struct drm_gpusvm *gpusvm,
+				    struct drm_gpusvm_pages *svm_pages)
 {
-	struct drm_gpusvm_pages *svm_pages = &range->pages;
-
 	lockdep_assert_held(&gpusvm->notifier_lock);
 
 	if (svm_pages->dma_addr) {
@@ -1072,8 +1069,8 @@ void drm_gpusvm_range_remove(struct drm_gpusvm *gpusvm,
 		return;
 
 	drm_gpusvm_notifier_lock(gpusvm);
-	__drm_gpusvm_range_unmap_pages(gpusvm, range, npages);
-	drm_gpusvm_range_free_pages(gpusvm, range);
+	__drm_gpusvm_unmap_pages(gpusvm, &range->pages, npages);
+	__drm_gpusvm_free_pages(gpusvm, &range->pages);
 	__drm_gpusvm_range_remove(notifier, range);
 	drm_gpusvm_notifier_unlock(gpusvm);
 
@@ -1138,6 +1135,28 @@ void drm_gpusvm_range_put(struct drm_gpusvm_range *range)
 }
 EXPORT_SYMBOL_GPL(drm_gpusvm_range_put);
 
+/**
+ * drm_gpusvm_pages_valid() - GPU SVM range pages valid
+ * @gpusvm: Pointer to the GPU SVM structure
+ * @svm_pages: Pointer to the GPU SVM pages structure
+ *
+ * This function determines if a GPU SVM range pages are valid. Expected be
+ * called holding gpusvm->notifier_lock and as the last step before committing a
+ * GPU binding. This is akin to a notifier seqno check in the HMM documentation
+ * but due to wider notifiers (i.e., notifiers which span multiple ranges) this
+ * function is required for finer grained checking (i.e., per range) if pages
+ * are valid.
+ *
+ * Return: True if GPU SVM range has valid pages, False otherwise
+ */
+static bool drm_gpusvm_pages_valid(struct drm_gpusvm *gpusvm,
+				   struct drm_gpusvm_pages *svm_pages)
+{
+	lockdep_assert_held(&gpusvm->notifier_lock);
+
+	return svm_pages->flags.has_devmem_pages || svm_pages->flags.has_dma_mapping;
+}
+
 /**
  * drm_gpusvm_range_pages_valid() - GPU SVM range pages valid
  * @gpusvm: Pointer to the GPU SVM structure
@@ -1155,11 +1174,7 @@ EXPORT_SYMBOL_GPL(drm_gpusvm_range_put);
 bool drm_gpusvm_range_pages_valid(struct drm_gpusvm *gpusvm,
 				  struct drm_gpusvm_range *range)
 {
-	struct drm_gpusvm_pages *svm_pages = &range->pages;
-
-	lockdep_assert_held(&gpusvm->notifier_lock);
-
-	return svm_pages->flags.has_devmem_pages || svm_pages->flags.has_dma_mapping;
+	return drm_gpusvm_pages_valid(gpusvm, &range->pages);
 }
 EXPORT_SYMBOL_GPL(drm_gpusvm_range_pages_valid);
 
@@ -1173,57 +1188,59 @@ EXPORT_SYMBOL_GPL(drm_gpusvm_range_pages_valid);
  *
  * Return: True if GPU SVM range has valid pages, False otherwise
  */
-static bool
-drm_gpusvm_range_pages_valid_unlocked(struct drm_gpusvm *gpusvm,
-				      struct drm_gpusvm_range *range)
+static bool drm_gpusvm_pages_valid_unlocked(struct drm_gpusvm *gpusvm,
+					    struct drm_gpusvm_pages *svm_pages)
 {
-	struct drm_gpusvm_pages *svm_pages = &range->pages;
 	bool pages_valid;
 
 	if (!svm_pages->dma_addr)
 		return false;
 
 	drm_gpusvm_notifier_lock(gpusvm);
-	pages_valid = drm_gpusvm_range_pages_valid(gpusvm, range);
+	pages_valid = drm_gpusvm_pages_valid(gpusvm, svm_pages);
 	if (!pages_valid)
-		drm_gpusvm_range_free_pages(gpusvm, range);
+		__drm_gpusvm_free_pages(gpusvm, svm_pages);
 	drm_gpusvm_notifier_unlock(gpusvm);
 
 	return pages_valid;
 }
 
 /**
- * drm_gpusvm_range_get_pages() - Get pages for a GPU SVM range
+ * drm_gpusvm_get_pages() - Get pages and populate GPU SVM pages struct
  * @gpusvm: Pointer to the GPU SVM structure
- * @range: Pointer to the GPU SVM range structure
+ * @svm_pages: The SVM pages to populate. This will contain the dma-addresses
+ * @mm: The mm corresponding to the CPU range
+ * @notifier: The corresponding notifier for the given CPU range
+ * @pages_start: Start CPU address for the pages
+ * @pages_end: End CPU address for the pages (exclusive)
  * @ctx: GPU SVM context
  *
- * This function gets pages for a GPU SVM range and ensures they are mapped for
- * DMA access.
+ * This function gets and maps pages for CPU range and ensures they are
+ * mapped for DMA access.
  *
  * Return: 0 on success, negative error code on failure.
  */
-int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
-			       struct drm_gpusvm_range *range,
-			       const struct drm_gpusvm_ctx *ctx)
+static int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
+				struct drm_gpusvm_pages *svm_pages,
+				struct mm_struct *mm,
+				struct mmu_interval_notifier *notifier,
+				unsigned long pages_start,
+				unsigned long pages_end,
+				const struct drm_gpusvm_ctx *ctx)
 {
-	struct drm_gpusvm_pages *svm_pages = &range->pages;
-	struct mmu_interval_notifier *notifier = &range->notifier->notifier;
 	struct hmm_range hmm_range = {
 		.default_flags = HMM_PFN_REQ_FAULT | (ctx->read_only ? 0 :
 			HMM_PFN_REQ_WRITE),
 		.notifier = notifier,
-		.start = drm_gpusvm_range_start(range),
-		.end = drm_gpusvm_range_end(range),
+		.start = pages_start,
+		.end = pages_end,
 		.dev_private_owner = gpusvm->device_private_page_owner,
 	};
-	struct mm_struct *mm = gpusvm->mm;
 	void *zdd;
 	unsigned long timeout =
 		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	unsigned long i, j;
-	unsigned long npages = npages_in_range(drm_gpusvm_range_start(range),
-					       drm_gpusvm_range_end(range));
+	unsigned long npages = npages_in_range(pages_start, pages_end);
 	unsigned long num_dma_mapped;
 	unsigned int order = 0;
 	unsigned long *pfns;
@@ -1236,7 +1253,7 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
 
 retry:
 	hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
-	if (drm_gpusvm_range_pages_valid_unlocked(gpusvm, range))
+	if (drm_gpusvm_pages_valid_unlocked(gpusvm, svm_pages))
 		goto set_seqno;
 
 	pfns = kvmalloc_array(npages, sizeof(*pfns), GFP_KERNEL);
@@ -1390,7 +1407,7 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
 	return 0;
 
 err_unmap:
-	__drm_gpusvm_range_unmap_pages(gpusvm, range, num_dma_mapped);
+	__drm_gpusvm_unmap_pages(gpusvm, svm_pages, num_dma_mapped);
 	drm_gpusvm_notifier_unlock(gpusvm);
 err_free:
 	kvfree(pfns);
@@ -1398,8 +1415,58 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
 		goto retry;
 	return err;
 }
+
+/**
+ * drm_gpusvm_range_get_pages() - Get pages for a GPU SVM range
+ * @gpusvm: Pointer to the GPU SVM structure
+ * @range: Pointer to the GPU SVM range structure
+ * @ctx: GPU SVM context
+ *
+ * This function gets pages for a GPU SVM range and ensures they are mapped for
+ * DMA access.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
+			       struct drm_gpusvm_range *range,
+			       const struct drm_gpusvm_ctx *ctx)
+{
+	return drm_gpusvm_get_pages(gpusvm, &range->pages, gpusvm->mm,
+				    &range->notifier->notifier,
+				    drm_gpusvm_range_start(range),
+				    drm_gpusvm_range_end(range), ctx);
+}
 EXPORT_SYMBOL_GPL(drm_gpusvm_range_get_pages);
 
+/**
+ * drm_gpusvm_unmap_pages() - Unmap GPU svm pages
+ * @gpusvm: Pointer to the GPU SVM structure
+ * @svm_pages: Pointer to the GPU SVM pages structure
+ * @npages: Number of pages in @svm_pages.
+ * @ctx: GPU SVM context
+ *
+ * This function unmaps pages associated with a GPU SVM pages struct. If
+ * @in_notifier is set, it is assumed that gpusvm->notifier_lock is held in
+ * write mode; if it is clear, it acquires gpusvm->notifier_lock in read mode.
+ * Must be called in the invalidate() callback of the corresponding notifier for
+ * IOMMU security model.
+ */
+static void drm_gpusvm_unmap_pages(struct drm_gpusvm *gpusvm,
+				   struct drm_gpusvm_pages *svm_pages,
+				   unsigned long npages,
+				   const struct drm_gpusvm_ctx *ctx)
+{
+	if (ctx->in_notifier)
+		lockdep_assert_held_write(&gpusvm->notifier_lock);
+	else
+		drm_gpusvm_notifier_lock(gpusvm);
+
+	__drm_gpusvm_unmap_pages(gpusvm, svm_pages, npages);
+
+	if (!ctx->in_notifier)
+		drm_gpusvm_notifier_unlock(gpusvm);
+}
+
 /**
  * drm_gpusvm_range_unmap_pages() - Unmap pages associated with a GPU SVM range
  * @gpusvm: Pointer to the GPU SVM structure
@@ -1419,15 +1486,7 @@ void drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
 	unsigned long npages = npages_in_range(drm_gpusvm_range_start(range),
 					       drm_gpusvm_range_end(range));
 
-	if (ctx->in_notifier)
-		lockdep_assert_held_write(&gpusvm->notifier_lock);
-	else
-		drm_gpusvm_notifier_lock(gpusvm);
-
-	__drm_gpusvm_range_unmap_pages(gpusvm, range, npages);
-
-	if (!ctx->in_notifier)
-		drm_gpusvm_notifier_unlock(gpusvm);
+	return drm_gpusvm_unmap_pages(gpusvm, &range->pages, npages, ctx);
 }
 EXPORT_SYMBOL_GPL(drm_gpusvm_range_unmap_pages);
 
-- 
2.51.0