[PATCH 1/1] drm/amdkfd: Remove prefault before migrating to VRAM

[Philip Yang]

If svm range no back system memory pages, migrate the range to GPU VRAM
don't need prefault on system pages to migrate pages. Instead we just
alloc VRAM pages and setup migrate->dst with the corresponding device
page and skip the page migration. The device page will be inserted to
PTE. Then CPU page fault will migrate the page back to system memory.

Signed-off-by: Philip Yang <Philip.Yang at amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 12 +++++-------
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c     | 22 ----------------------
 drivers/gpu/drm/amd/amdkfd/kfd_svm.h     |  2 --
 3 files changed, 5 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
index 373e5bfd4e91..d3ebbde21241 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
@@ -322,12 +322,13 @@ svm_migrate_copy_to_vram(struct amdgpu_device *adev, struct svm_range *prange,
 	for (i = j = 0; i < npages; i++) {
 		struct page *spage;
 
+		dst[i] = cursor.start + (j << PAGE_SHIFT);
+		migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
+		svm_migrate_get_vram_page(prange, migrate->dst[i]);
+		migrate->dst[i] = migrate_pfn(migrate->dst[i]);
+
 		spage = migrate_pfn_to_page(migrate->src[i]);
 		if (spage && !is_zone_device_page(spage)) {
-			dst[i] = cursor.start + (j << PAGE_SHIFT);
-			migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
-			svm_migrate_get_vram_page(prange, migrate->dst[i]);
-			migrate->dst[i] = migrate_pfn(migrate->dst[i]);
 			src[i] = dma_map_page(dev, spage, 0, PAGE_SIZE,
 					      DMA_TO_DEVICE);
 			r = dma_mapping_error(dev, src[i]);
@@ -522,9 +523,6 @@ svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t best_loc,
 	pr_debug("svms 0x%p [0x%lx 0x%lx] to gpu 0x%x\n", prange->svms,
 		 prange->start, prange->last, best_loc);
 
-	/* FIXME: workaround for page locking bug with invalid pages */
-	svm_range_prefault(prange, mm, SVM_ADEV_PGMAP_OWNER(adev));
-
 	start = prange->start << PAGE_SHIFT;
 	end = (prange->last + 1) << PAGE_SHIFT;
 
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 11074cc8c333..cf5b4005534c 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -3181,28 +3181,6 @@ svm_range_best_prefetch_location(struct svm_range *prange)
 	return best_loc;
 }
 
-/* FIXME: This is a workaround for page locking bug when some pages are
- * invalid during migration to VRAM
- */
-void svm_range_prefault(struct svm_range *prange, struct mm_struct *mm,
-			void *owner)
-{
-	struct hmm_range *hmm_range;
-	int r;
-
-	if (prange->validated_once)
-		return;
-
-	r = amdgpu_hmm_range_get_pages(&prange->notifier, mm, NULL,
-				       prange->start << PAGE_SHIFT,
-				       prange->npages, &hmm_range,
-				       false, true, owner);
-	if (!r) {
-		amdgpu_hmm_range_get_pages_done(hmm_range);
-		prange->validated_once = true;
-	}
-}
-
 /* svm_range_trigger_migration - start page migration if prefetch loc changed
  * @mm: current process mm_struct
  * @prange: svm range structure
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
index cfac13ad06ef..012c53729516 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
@@ -181,8 +181,6 @@ void schedule_deferred_list_work(struct svm_range_list *svms);
 void svm_range_dma_unmap(struct device *dev, dma_addr_t *dma_addr,
 			 unsigned long offset, unsigned long npages);
 void svm_range_free_dma_mappings(struct svm_range *prange);
-void svm_range_prefault(struct svm_range *prange, struct mm_struct *mm,
-			void *owner);
 int svm_range_get_info(struct kfd_process *p, uint32_t *num_svm_ranges,
 		       uint64_t *svm_priv_data_size);
 int kfd_criu_checkpoint_svm(struct kfd_process *p,
-- 
2.35.1