[PATCH 2/3] drm/amdkfd: Fix the case that vm range is hole at svm_migrate_copy_to_vram

[Xiaogang.Chen <xiaogang.chen@amd.com>]

From: Xiaogang Chen <xiaogang.chen@amd.com>

When migration vm range is hole at cpu side(MIGRATE_PFN_MIGRATE set +
MIGRATE_PFN_VALID unset) driver still allocates device pages. There is no
dma map of src pages and migration. j is 0 and svm_migrate_copy_memory_gart()
will return an uninitialized r. That can trigger out_free_vram_pages to drop
all VRAM just set up.

Initialize r and only call the last svm_migrate_copy_memory_gart if j > 0.

Current code postponed the last page to the final copy. This patch flushes on
the last page when reach to the end of current drm_buddy_block; avoids another
svm_migrate_copy_memory_gart.

Signed-off-by: Xiaogang Chen <xiaogang.chen@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
index aea82da5f575..263dae49bb3e 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
@@ -284,7 +284,7 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct svm_range *prange,
 	dma_addr_t *src;
 	u64 *dst;
 	u64 i, j;
-	int r;
+	int r = 0;
 
 	pr_debug("svms 0x%p [0x%lx 0x%lx 0x%llx]\n", prange->svms, prange->start,
 		 prange->last, ttm_res_offset);
@@ -310,6 +310,7 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct svm_range *prange,
 					      DMA_BIDIRECTIONAL);
 			r = dma_mapping_error(dev, src[i]);
 			if (r) {
+				src[i] = 0;
 				dev_err(dev, "%s: fail %d dma_map_page\n",
 					__func__, r);
 				goto out_free_vram_pages;
@@ -334,7 +335,8 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct svm_range *prange,
 		pr_debug_ratelimited("dma mapping src to 0x%llx, pfn 0x%lx\n",
 				     src[i] >> PAGE_SHIFT, page_to_pfn(spage));
 
-		if (j >= (cursor.size >> PAGE_SHIFT) - 1 && i < npages - 1) {
+		/* accumulated j + 1 pages reach end of current drm_buddy_block */
+		if (j + 1 >= (cursor.size >> PAGE_SHIFT)) {
 			r = svm_migrate_copy_memory_gart(adev, src + i - j,
 							 dst + i - j, j + 1,
 							 FROM_RAM_TO_VRAM,
@@ -348,7 +350,8 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct svm_range *prange,
 		}
 	}
 
-	r = svm_migrate_copy_memory_gart(adev, src + i - j, dst + i - j, j,
+	if (j > 0)
+		r = svm_migrate_copy_memory_gart(adev, src + i - j, dst + i - j, j,
 					 FROM_RAM_TO_VRAM, mfence);
 
 out_free_vram_pages:
-- 
2.34.1