[Mesa-dev] [PATCH 1/3] i965: Ensure that intel_bufferobj_map_range meets alignment guarantees

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

No piglit regressions on IVB.

With minor tweaks to the arb_map_buffer_alignment-map-invalidate-range
test (disable the extension check, set alignment to 64 instead of
querying), the i965 driver would fail the test without this patch (as
predicted by Eric).  With this patch, it passes.

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
Cc: Eric Anholt <eric at anholt.net>
Cc: Siavash Eliasi <siavashserver at gmail.com>
---
 src/mesa/drivers/dri/i965/intel_buffer_objects.c | 28 ++++++++++++++++++------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/intel_buffer_objects.c b/src/mesa/drivers/dri/i965/intel_buffer_objects.c
index cab805a..7bf8cae 100644
--- a/src/mesa/drivers/dri/i965/intel_buffer_objects.c
+++ b/src/mesa/drivers/dri/i965/intel_buffer_objects.c
@@ -359,20 +359,28 @@ intel_bufferobj_map_range(struct gl_context * ctx,
     */
    if ((access & GL_MAP_INVALIDATE_RANGE_BIT) &&
        drm_intel_bo_busy(intel_obj->buffer)) {
+      /* Ensure that the base alignment of the allocation meets the alignment
+       * guarantees the driver has advertised to the application.
+       */
+      const unsigned alignment = MAX2(64, ctx->Const.MinMapBufferAlignment);
+      const unsigned extra = (uintptr_t) offset % alignment;
+
       if (access & GL_MAP_FLUSH_EXPLICIT_BIT) {
-	 intel_obj->range_map_buffer = malloc(length);
-	 obj->Pointer = intel_obj->range_map_buffer;
+         intel_obj->range_map_buffer = _mesa_align_malloc(length + extra,
+                                                          alignment);
+         obj->Pointer = intel_obj->range_map_buffer + extra;
       } else {
 	 intel_obj->range_map_bo = drm_intel_bo_alloc(brw->bufmgr,
 						      "range map",
-						      length, 64);
+                                                      length + extra,
+                                                      alignment);
 	 if (!(access & GL_MAP_READ_BIT)) {
 	    drm_intel_gem_bo_map_gtt(intel_obj->range_map_bo);
 	 } else {
 	    drm_intel_bo_map(intel_obj->range_map_bo,
 			     (access & GL_MAP_WRITE_BIT) != 0);
 	 }
-	 obj->Pointer = intel_obj->range_map_bo->virtual;
+	 obj->Pointer = intel_obj->range_map_bo->virtual + extra;
       }
       return obj->Pointer;
    }
@@ -424,7 +432,11 @@ intel_bufferobj_flush_mapped_range(struct gl_context *ctx,
 
    temp_bo = drm_intel_bo_alloc(brw->bufmgr, "range map flush", length, 64);
 
-   drm_intel_bo_subdata(temp_bo, 0, length, intel_obj->range_map_buffer);
+   /* Use obj->Pointer instead of intel_obj->range_map_buffer because the
+    * former points to the actual mapping while the latter may be offset to
+    * meet alignment guarantees.
+    */
+   drm_intel_bo_subdata(temp_bo, 0, length, obj->Pointer);
 
    intel_emit_linear_blit(brw,
 			  intel_obj->buffer, obj->Offset + offset,
@@ -456,14 +468,16 @@ intel_bufferobj_unmap(struct gl_context * ctx, struct gl_buffer_object *obj)
        * usage inside of a batchbuffer.
        */
       intel_batchbuffer_emit_mi_flush(brw);
-      free(intel_obj->range_map_buffer);
+      _mesa_align_free(intel_obj->range_map_buffer);
       intel_obj->range_map_buffer = NULL;
    } else if (intel_obj->range_map_bo != NULL) {
+      const unsigned extra = obj->Pointer - intel_obj->range_map_bo->virtual;
+
       drm_intel_bo_unmap(intel_obj->range_map_bo);
 
       intel_emit_linear_blit(brw,
 			     intel_obj->buffer, obj->Offset,
-			     intel_obj->range_map_bo, 0,
+			     intel_obj->range_map_bo, extra,
 			     obj->Length);
       intel_bufferobj_mark_gpu_usage(intel_obj, obj->Offset, obj->Length);
 
-- 
1.8.1.4