[PATCH 2/3] drm/xe: Introduce a helper to free sg table

[Oak Zeng]

Introduce xe_userptr_free_sg helper to dma-unmap all
addresses in userptr's sg table and free sg table.

Signed-off-by: Oak Zeng <oak.zeng at intel.com>
Suggested by: Matthew Brost <matthew.brost at intel.com>
---
 drivers/gpu/drm/xe/xe_hmm.c | 30 ++++++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_hmm.h |  1 +
 2 files changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_hmm.c b/drivers/gpu/drm/xe/xe_hmm.c
index 4011207630a5..427c6bc49949 100644
--- a/drivers/gpu/drm/xe/xe_hmm.c
+++ b/drivers/gpu/drm/xe/xe_hmm.c
@@ -3,6 +3,7 @@
  * Copyright © 2024 Intel Corporation
  */
 
+#include <linux/scatterlist.h>
 #include <linux/mmu_notifier.h>
 #include <linux/dma-mapping.h>
 #include <linux/memremap.h>
@@ -107,6 +108,32 @@ static int xe_build_sg(struct xe_device *xe, struct hmm_range *range,
 	return ret;
 }
 
+/**
+ * xe_userptr_free_sg() - Free the scatter gather table of userptr
+ *
+ * @uvma: the userptr vma which hold the scatter gather table
+ *
+ * With function xe_userptr_populate_range, we allocate storage of
+ * the userptr sg table. This is a helper function to free this
+ * sg table, and dma unmap the address in the table.
+ */
+void xe_userptr_free_sg(struct xe_userptr_vma *uvma)
+{
+	struct xe_userptr *userptr = &uvma->userptr;
+	struct xe_vma *vma = &uvma->vma;
+	bool write = !xe_vma_read_only(vma);
+	struct xe_vm *vm = xe_vma_vm(vma);
+	struct xe_device *xe = vm->xe;
+	struct device *dev = xe->drm.dev;
+
+	xe_assert(xe, userptr->sg);
+	dma_unmap_sgtable(dev, userptr->sg,
+			write ? DMA_BIDIRECTIONAL : DMA_TO_DEVICE, 0);
+
+	sg_free_table(userptr->sg);
+	userptr->sg = NULL;
+}
+
 /**
  * xe_userptr_populate_range() - Populate physical pages of a virtual
  * address range
@@ -156,6 +183,9 @@ int xe_userptr_populate_range(struct xe_userptr_vma *uvma)
 	if (notifier_seq == userptr->notifier_seq)
 		return 0;
 
+	if (userptr->sg)
+		xe_userptr_free_sg(uvma);
+
 	npages = xe_npages_in_range(start, end);
 	pfns = kvmalloc_array(npages, sizeof(*pfns), GFP_KERNEL);
 	if (unlikely(!pfns))
diff --git a/drivers/gpu/drm/xe/xe_hmm.h b/drivers/gpu/drm/xe/xe_hmm.h
index 91686a751711..7bb49bbde5a4 100644
--- a/drivers/gpu/drm/xe/xe_hmm.h
+++ b/drivers/gpu/drm/xe/xe_hmm.h
@@ -15,3 +15,4 @@ static inline int xe_userptr_populate_range(struct xe_userptr_vma *uvma)
 	return -ENODEV;
 }
 #endif
+void xe_userptr_free_sg(struct xe_userptr_vma *uvma);
-- 
2.26.3