drm/i915: Add support for mandatory cmdparsing

commit 311a50e7 upstream.

The existing cmdparser for gen7 can be bypassed by specifying
batch_len=0 in the execbuf call. This is safe because bypassing
simply reduces the cmd-set available.

In a later patch we will introduce cmdparsing for gen9, as a
security measure, which must be strictly enforced since without
it we are vulnerable to DoS attacks.

Introduce the concept of 'required' cmd parsing that cannot be
bypassed by submitting zero-length bb's.

v2: rebase (Mika)
v2: rebase (Mika)
v3: fix conflict on engine flags (Mika)
Signed-off-by: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris.p.wilson@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -916,7 +916,7 @@ void intel_engine_init_cmd_parser(struct intel_engine_cs *engine)
 		return;
 	}
 
-	engine->flags |= I915_ENGINE_NEEDS_CMD_PARSER;
+	engine->flags |= I915_ENGINE_USING_CMD_PARSER;
 }
 
 /**
@@ -928,7 +928,7 @@ void intel_engine_init_cmd_parser(struct intel_engine_cs *engine)
  */
 void intel_engine_cleanup_cmd_parser(struct intel_engine_cs *engine)
 {
-	if (!intel_engine_needs_cmd_parser(engine))
+	if (!intel_engine_using_cmd_parser(engine))
 		return;
 
 	fini_hash_table(engine);
@@ -1316,7 +1316,7 @@ int i915_cmd_parser_get_version(struct drm_i915_private *dev_priv)
 
 	/* If the command parser is not enabled, report 0 - unsupported */
 	for_each_engine(engine, dev_priv) {
-		if (intel_engine_needs_cmd_parser(engine)) {
+		if (intel_engine_using_cmd_parser(engine)) {
 			active = true;
 			break;
 		}

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -1716,7 +1716,8 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	}
 
 	params->args_batch_start_offset = args->batch_start_offset;
-	if (intel_engine_needs_cmd_parser(engine) && args->batch_len) {
+	if (intel_engine_requires_cmd_parser(engine) ||
+	    (intel_engine_using_cmd_parser(engine) && args->batch_len)) {
 		struct i915_vma *vma;
 
 		vma = i915_gem_execbuffer_parse(engine, &shadow_exec_entry,

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -341,7 +341,8 @@ struct intel_engine_cs {
 
 	struct intel_engine_hangcheck hangcheck;
 
-#define I915_ENGINE_NEEDS_CMD_PARSER BIT(0)
+#define I915_ENGINE_USING_CMD_PARSER	BIT(0)
+#define I915_ENGINE_REQUIRES_CMD_PARSER	BIT(3)
 	unsigned int flags;
 
 	/*
@@ -375,9 +376,16 @@ intel_engine_initialized(const struct intel_engine_cs *engine)
 	return engine->i915 != NULL;
 }
 
-static inline bool intel_engine_needs_cmd_parser(struct intel_engine_cs *engine)
+static inline bool
+intel_engine_using_cmd_parser(const struct intel_engine_cs *engine)
+{
+	return engine->flags & I915_ENGINE_USING_CMD_PARSER;
+}
+
+static inline bool
+intel_engine_requires_cmd_parser(const struct intel_engine_cs *engine)
 {
-	return engine->flags & I915_ENGINE_NEEDS_CMD_PARSER;
+	return engine->flags & I915_ENGINE_REQUIRES_CMD_PARSER;
 }
 
 static inline unsigned int