drm/amdkfd: Fix SVM_ATTR_PREFERRED_LOC

The preferred location should be used as the migration destination
whenever it is accessible by the faulting GPU. System memory is always
accessible. Peer memory is accessible if it's in the same XGMI hive.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_svm.c

@@ -2261,7 +2261,7 @@ svm_range_from_addr(struct svm_range_list *svms, unsigned long addr,
  * migration if actual loc is not best location, then update GPU page table
  * mapping to the best location.
  *
- * If vm fault gpu is range preferred loc, the best_loc is preferred loc.
+ * If the preferred loc is accessible by faulting GPU, use preferred loc.
  * If vm fault gpu idx is on range ACCESSIBLE bitmap, best_loc is vm fault gpu
  * If vm fault gpu idx is on range ACCESSIBLE_IN_PLACE bitmap, then
  *    if range actual loc is cpu, best_loc is cpu
@@ -2278,7 +2278,7 @@ svm_range_best_restore_location(struct svm_range *prange,
 				struct amdgpu_device *adev,
 				int32_t *gpuidx)
 {
-	struct amdgpu_device *bo_adev;
+	struct amdgpu_device *bo_adev, *preferred_adev;
 	struct kfd_process *p;
 	uint32_t gpuid;
 	int r;
@@ -2291,8 +2291,16 @@ svm_range_best_restore_location(struct svm_range *prange,
 		return -1;
 	}
 
-	if (prange->preferred_loc == gpuid)
+	if (prange->preferred_loc == gpuid ||
+	    prange->preferred_loc == KFD_IOCTL_SVM_LOCATION_SYSMEM) {
 		return prange->preferred_loc;
+	} else if (prange->preferred_loc != KFD_IOCTL_SVM_LOCATION_UNDEFINED) {
+		preferred_adev = svm_range_get_adev_by_id(prange,
+							prange->preferred_loc);
+		if (amdgpu_xgmi_same_hive(adev, preferred_adev))
+			return prange->preferred_loc;
+		/* fall through */
+	}
 
 	if (test_bit(*gpuidx, prange->bitmap_access))
 		return gpuid;