drm/i915: Skip over MI_NOOP when parsing

Though less likely in practice, igt uses MI_NOOP frequently to pad out
its batch buffers. The lookup and valiation of so many MI_NOOP command
descriptions is noticeable, though the side-effect of poisoning the
last-validated-command cache is more likely to impact upon real CS.

Testcase: igt/gen9_exec_parse/bb-large
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201001102632.18789-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index e889702..9326595 100644 (file)
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -1452,43 +1452,42 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
         * space. Parsing should be faster in some cases this way.
         */
        batch_end = cmd + batch_length / sizeof(*batch_end);
-       do {
-               u32 length;
-
-               if (*cmd == MI_BATCH_BUFFER_END)
-                       break;
-
-               desc = find_cmd(engine, *cmd, desc, &default_desc);
-               if (!desc) {
-                       DRM_DEBUG("CMD: Unrecognized command: 0x%08X\n", *cmd);
-                       ret = -EINVAL;
-                       break;
-               }
+       while (*cmd != MI_BATCH_BUFFER_END) {
+               u32 length = 1;
+
+               if (*cmd != MI_NOOP) { /* MI_NOOP == 0 */
+                       desc = find_cmd(engine, *cmd, desc, &default_desc);
+                       if (!desc) {
+                               DRM_DEBUG("CMD: Unrecognized command: 0x%08X\n", *cmd);
+                               ret = -EINVAL;
+                               break;
+                       }
 
-               if (desc->flags & CMD_DESC_FIXED)
-                       length = desc->length.fixed;
-               else
-                       length = (*cmd & desc->length.mask) + LENGTH_BIAS;
+                       if (desc->flags & CMD_DESC_FIXED)
+                               length = desc->length.fixed;
+                       else
+                               length = (*cmd & desc->length.mask) + LENGTH_BIAS;
 
-               if ((batch_end - cmd) < length) {
-                       DRM_DEBUG("CMD: Command length exceeds batch length: 0x%08X length=%u batchlen=%td\n",
-                                 *cmd,
-                                 length,
-                                 batch_end - cmd);
-                       ret = -EINVAL;
-                       break;
-               }
+                       if ((batch_end - cmd) < length) {
+                               DRM_DEBUG("CMD: Command length exceeds batch length: 0x%08X length=%u batchlen=%td\n",
+                                         *cmd,
+                                         length,
+                                         batch_end - cmd);
+                               ret = -EINVAL;
+                               break;
+                       }
 
-               if (!check_cmd(engine, desc, cmd, length)) {
-                       ret = -EACCES;
-                       break;
-               }
+                       if (!check_cmd(engine, desc, cmd, length)) {
+                               ret = -EACCES;
+                               break;
+                       }
 
-               if (cmd_desc_is(desc, MI_BATCH_BUFFER_START)) {
-                       ret = check_bbstart(cmd, offset, length, batch_length,
-                                           batch_addr, shadow_addr,
-                                           jump_whitelist);
-                       break;
+                       if (cmd_desc_is(desc, MI_BATCH_BUFFER_START)) {
+                               ret = check_bbstart(cmd, offset, length, batch_length,
+                                                   batch_addr, shadow_addr,
+                                                   jump_whitelist);
+                               break;
+                       }
                }
 
                if (!IS_ERR_OR_NULL(jump_whitelist))
@@ -1501,7 +1500,7 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
                        ret = -EINVAL;
                        break;
                }
-       } while (1);
+       }
 
        if (trampoline) {
                /*