[PATCH v3] drm/xe: add system memory page iterator support to xe_res_cursor

[Andrzej Hajda]

Currently xe_res_cursor allows iteration only over DMA side of sg tables.
Adding possibility to iterate over pages allows the use of cursor in more
contexts.

v2: fixed wording in commit message (Jonathan)
v3: indentation and author fixes (checkpatch)

Signed-off-by: Andrzej Hajda <andrzej.hajda at intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
---
- Link to v1: https://lore.kernel.org/r/20241009-xe_res_cursor_add_page_iterator-v1-1-c883446e5770@intel.com
- Link to v2: https://lore.kernel.org/r/20241011-xe_res_cursor_add_page_iterator-v2-1-367b74c1cc29@intel.com
---
Hi all,

This patch is required to proper implementation of userptr_vma access
in configurations with iommu turned on[1]. Required by upcoming eudebug
feature.

[1]: https://lore.kernel.org/intel-xe/20241001144306.1991001-13-mika.kuoppala@linux.intel.com/

Regards
Andrzej
---
 drivers/gpu/drm/xe/xe_res_cursor.h | 51 +++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_res_cursor.h b/drivers/gpu/drm/xe/xe_res_cursor.h
index dca374b6521c..610407f23dbd 100644
--- a/drivers/gpu/drm/xe/xe_res_cursor.h
+++ b/drivers/gpu/drm/xe/xe_res_cursor.h
@@ -129,18 +129,35 @@ static inline void __xe_res_sg_next(struct xe_res_cursor *cur)
 {
 	struct scatterlist *sgl = cur->sgl;
 	u64 start = cur->start;
+	unsigned int len;
 
-	while (start >= sg_dma_len(sgl)) {
-		start -= sg_dma_len(sgl);
+	while (true) {
+		len = (cur->mem_type == XE_PL_SYSTEM) ? sgl->length : sg_dma_len(sgl);
+		if (start < len)
+			break;
+		start -= len;
 		sgl = sg_next(sgl);
 		XE_WARN_ON(!sgl);
 	}
-
 	cur->start = start;
-	cur->size = sg_dma_len(sgl) - start;
+	cur->size = len - start;
 	cur->sgl = sgl;
 }
 
+static inline void __xe_res_first_sg(const struct sg_table *sg,
+				     u64 start, u64 size,
+				     struct xe_res_cursor *cur, u32 mem_type)
+{
+	XE_WARN_ON(!sg);
+	cur->node = NULL;
+	cur->start = start;
+	cur->remaining = size;
+	cur->size = 0;
+	cur->sgl = sg->sgl;
+	cur->mem_type = mem_type;
+	__xe_res_sg_next(cur);
+}
+
 /**
  * xe_res_first_sg - initialize a xe_res_cursor with a scatter gather table
  *
@@ -155,14 +172,24 @@ static inline void xe_res_first_sg(const struct sg_table *sg,
 				   u64 start, u64 size,
 				   struct xe_res_cursor *cur)
 {
-	XE_WARN_ON(!sg);
-	cur->node = NULL;
-	cur->start = start;
-	cur->remaining = size;
-	cur->size = 0;
-	cur->sgl = sg->sgl;
-	cur->mem_type = XE_PL_TT;
-	__xe_res_sg_next(cur);
+	__xe_res_first_sg(sg, start, size, cur, XE_PL_TT);
+}
+
+/**
+ * xe_res_first_sg_system - initialize a xe_res_cursor for iterate system memory pages
+ *
+ * @sg: scatter gather table to walk
+ * @start: Start of the range
+ * @size: Size of the range
+ * @cur: cursor object to initialize
+ *
+ * Start walking over the range of allocations between @start and @size
+ */
+static inline void xe_res_first_sg_system(const struct sg_table *sg,
+					  u64 start, u64 size,
+					  struct xe_res_cursor *cur)
+{
+	__xe_res_first_sg(sg, start, size, cur, XE_PL_SYSTEM);
 }
 
 /**

---
base-commit: f1561e6c62b5b5c3fe0276f2fbe7325e0d7c262d
change-id: 20241009-xe_res_cursor_add_page_iterator-d29d73c3eb99

Best regards,
-- 
Andrzej Hajda <andrzej.hajda at intel.com>