drm/xe/bo: Evict VRAM to TT rather than to system

The main difference is that we don't bounce and sync on eviction, allowing
for pipelined eviction. Moving forward we also need to be careful with
dma mappings which can be released in SYSTEM but may remain in TT.

v2:
- Remove a stale comment (Matthew Brost)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230626181741.32820-5-thomas.hellstrom@linux.intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/tests/xe_dma_buf.c

@@ -72,7 +72,7 @@ static void check_residency(struct kunit *test, struct xe_bo *exported,
 	}
 
 	/* Verify that also importer has been evicted to SYSTEM */
-	if (!xe_bo_is_mem_type(imported, XE_PL_SYSTEM)) {
+	if (exported != imported && !xe_bo_is_mem_type(imported, XE_PL_SYSTEM)) {
 		KUNIT_FAIL(test, "Importer wasn't properly evicted.\n");
 		return;
 	}
@@ -91,8 +91,7 @@ static void check_residency(struct kunit *test, struct xe_bo *exported,
 	 * possible, saving a migration step as the transfer is just
 	 * likely as fast from system memory.
 	 */
-	if (params->force_different_devices &&
-	    params->mem_mask & XE_BO_CREATE_SYSTEM_BIT)
+	if (params->mem_mask & XE_BO_CREATE_SYSTEM_BIT)
 		KUNIT_EXPECT_TRUE(test, xe_bo_is_mem_type(exported, XE_PL_TT));
 	else
 		KUNIT_EXPECT_TRUE(test, xe_bo_is_mem_type(exported, mem_type));

drivers/gpu/drm/xe/xe_bo.c

@@ -40,6 +40,20 @@ static struct ttm_placement sys_placement = {
 	.busy_placement = &sys_placement_flags,
 };
 
+static const struct ttm_place tt_placement_flags = {
+	.fpfn = 0,
+	.lpfn = 0,
+	.mem_type = XE_PL_TT,
+	.flags = 0,
+};
+
+static struct ttm_placement tt_placement = {
+	.num_placement = 1,
+	.placement = &tt_placement_flags,
+	.num_busy_placement = 1,
+	.busy_placement = &sys_placement_flags,
+};
+
 bool mem_type_is_vram(u32 mem_type)
 {
 	return mem_type >= XE_PL_VRAM0 && mem_type != XE_PL_STOLEN;
@@ -225,9 +239,10 @@ static void xe_evict_flags(struct ttm_buffer_object *tbo,
 	case XE_PL_VRAM0:
 	case XE_PL_VRAM1:
 	case XE_PL_STOLEN:
+		*placement = tt_placement;
+		break;
 	case XE_PL_TT:
 	default:
-		/* for now kick out to system */
 		*placement = sys_placement;
 		break;
 	}

drivers/gpu/drm/xe/xe_dma_buf.c

@@ -81,13 +81,10 @@ static struct sg_table *xe_dma_buf_map(struct dma_buf_attachment *attach,
 		return ERR_PTR(-EOPNOTSUPP);
 
 	if (!xe_bo_is_pinned(bo)) {
-		if (!attach->peer2peer ||
-		    bo->ttm.resource->mem_type == XE_PL_SYSTEM) {
-			if (xe_bo_can_migrate(bo, XE_PL_TT))
+		if (!attach->peer2peer)
 			r = xe_bo_migrate(bo, XE_PL_TT);
 		else
 			r = xe_bo_validate(bo, NULL, false);
-		}
 		if (r)
 			return ERR_PTR(r);
 	}