drm/i915: Reject commands that would store to global HWS page

PIPE_CONTROL and MI_FLUSH_DW have bits that would write to the
hardware status page. The driver stores request tracking info
there, so don't let userspace overwrite it.

v2: trailing comma fix, rebased

Signed-off-by: Brad Volkin <bradley.d.volkin@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -193,7 +193,8 @@ static const struct drm_i915_cmd_descriptor render_cmds[] = {
 	      },
 	      {
 			.offset = 1,
-		        .mask = PIPE_CONTROL_GLOBAL_GTT_IVB,
+		        .mask = (PIPE_CONTROL_GLOBAL_GTT_IVB |
+				 PIPE_CONTROL_STORE_DATA_INDEX),
 			.expected = 0,
 			.condition_offset = 1,
 			.condition_mask = PIPE_CONTROL_POST_SYNC_OP_MASK,
@@ -242,6 +243,13 @@ static const struct drm_i915_cmd_descriptor video_cmds[] = {
 			.expected = 0,
 			.condition_offset = 0,
 			.condition_mask = MI_FLUSH_DW_OP_MASK,
+	      },
+	      {
+			.offset = 0,
+			.mask = MI_FLUSH_DW_STORE_INDEX,
+			.expected = 0,
+			.condition_offset = 0,
+			.condition_mask = MI_FLUSH_DW_OP_MASK,
 	      }},						       ),
 	CMD(  MI_CONDITIONAL_BATCH_BUFFER_END,  SMI,   !F,  0xFF,   B,
 	      .bits = {{
@@ -278,6 +286,13 @@ static const struct drm_i915_cmd_descriptor vecs_cmds[] = {
 			.expected = 0,
 			.condition_offset = 0,
 			.condition_mask = MI_FLUSH_DW_OP_MASK,
+	      },
+	      {
+			.offset = 0,
+			.mask = MI_FLUSH_DW_STORE_INDEX,
+			.expected = 0,
+			.condition_offset = 0,
+			.condition_mask = MI_FLUSH_DW_OP_MASK,
 	      }},						       ),
 	CMD(  MI_CONDITIONAL_BATCH_BUFFER_END,  SMI,   !F,  0xFF,   B,
 	      .bits = {{
@@ -308,6 +323,13 @@ static const struct drm_i915_cmd_descriptor blt_cmds[] = {
 			.expected = 0,
 			.condition_offset = 0,
 			.condition_mask = MI_FLUSH_DW_OP_MASK,
+	      },
+	      {
+			.offset = 0,
+			.mask = MI_FLUSH_DW_STORE_INDEX,
+			.expected = 0,
+			.condition_offset = 0,
+			.condition_mask = MI_FLUSH_DW_OP_MASK,
 	      }},						       ),
 	CMD(  COLOR_BLT,                        S2D,   !F,  0x3F,   S  ),
 	CMD(  SRC_COPY_BLT,                     S2D,   !F,  0x3F,   S  ),

drivers/gpu/drm/i915/i915_reg.h

@@ -336,6 +336,7 @@
 #define GFX_OP_PIPE_CONTROL(len)	((0x3<<29)|(0x3<<27)|(0x2<<24)|(len-2))
 #define   PIPE_CONTROL_GLOBAL_GTT_IVB			(1<<24) /* gen7+ */
 #define   PIPE_CONTROL_MMIO_WRITE			(1<<23)
+#define   PIPE_CONTROL_STORE_DATA_INDEX			(1<<21)
 #define   PIPE_CONTROL_CS_STALL				(1<<20)
 #define   PIPE_CONTROL_TLB_INVALIDATE			(1<<18)
 #define   PIPE_CONTROL_QW_WRITE				(1<<14)