[PATCH] drm/amdkfd: restore userptr ignore bad address error

[Philip Yang]

The userptr can be unmapped by application and still registered to
driver, restore userptr work return user pages will get -EFAULT bad
address error. Pretend this error as succeed. GPU access this userptr
will have VM fault later, it is better than application soft hangs with
stalled user mode queues.

Signed-off-by: Philip Yang <Philip.Yang at amd.com>
---
 .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c  | 27 ++++++++++++-------
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c       |  3 +++
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index cdf46bd0d8d5..6f01c6145a87 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -2041,19 +2041,26 @@ static int update_invalid_user_pages(struct amdkfd_process_info *process_info,
 		/* Get updated user pages */
 		ret = amdgpu_ttm_tt_get_user_pages(bo, bo->tbo.ttm->pages);
 		if (ret) {
-			pr_debug("%s: Failed to get user pages: %d\n",
-				__func__, ret);
+			pr_debug("Failed %d to get user pages\n", ret);
+
+			/* Return -EFAULT bad address error as success. It will
+			 * fail later with a VM fault if the GPU tries to access
+			 * it. Better than hanging indefinitely with stalled
+			 * user mode queues.
+			 *
+			 * Return other error -EBUSY or -ENOMEM to retry restore
+			 */
+			if (ret != -EFAULT)
+				return ret;
+		} else {
 
-			/* Return error -EBUSY or -ENOMEM, retry restore */
-			return ret;
+			/*
+			 * FIXME: Cannot ignore the return code, must hold
+			 * notifier_lock
+			 */
+			amdgpu_ttm_tt_get_user_pages_done(bo->tbo.ttm);
 		}
 
-		/*
-		 * FIXME: Cannot ignore the return code, must hold
-		 * notifier_lock
-		 */
-		amdgpu_ttm_tt_get_user_pages_done(bo->tbo.ttm);
-
 		/* Mark the BO as valid unless it was invalidated
 		 * again concurrently.
 		 */
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index d784f8d3a834..ae6694f2c73d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -693,6 +693,9 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
 	r = amdgpu_hmm_range_get_pages(&bo->notifier, mm, pages, start,
 				       ttm->num_pages, &gtt->range, readonly,
 				       false, NULL);
+	if (r)
+		pr_debug("failed %d to get user pages 0x%llx\n", r, start);
+
 out_putmm:
 	mmput(mm);
 
-- 
2.17.1