drm/i915: Add support for mandatory cmdparsing

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 <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: Takashi Iwai <[email protected]>
Cc: Tyler Hicks <[email protected]>
Signed-off-by: Mika Kuoppala <[email protected]>
Reviewed-by: Chris Wilson <[email protected]>

Author: jbloomfi-intel

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -296,7 +296,8 @@ static inline u64 gen8_noncanonical_addr(u64 address)
 
 static inline bool eb_use_cmdparser(const struct i915_execbuffer *eb)
 {
-	return intel_engine_needs_cmd_parser(eb->engine) && eb->batch_len;
+	return intel_engine_requires_cmd_parser(eb->engine) ||
+		(intel_engine_using_cmd_parser(eb->engine) && eb->batch_len);
 }
 
 static int eb_create(struct i915_execbuffer *eb)

drivers/gpu/drm/i915/gt/intel_engine_types.h

@@ -475,12 +475,13 @@ 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_SUPPORTS_STATS   BIT(1)
 #define I915_ENGINE_HAS_PREEMPTION   BIT(2)
 #define I915_ENGINE_HAS_SEMAPHORES   BIT(3)
 #define I915_ENGINE_NEEDS_BREADCRUMB_TASKLET BIT(4)
 #define I915_ENGINE_IS_VIRTUAL       BIT(5)
+#define I915_ENGINE_REQUIRES_CMD_PARSER BIT(7)
 	unsigned int flags;
 
 	/*
@@ -541,9 +542,15 @@ struct intel_engine_cs {
 };
 
 static inline bool
-intel_engine_needs_cmd_parser(const struct intel_engine_cs *engine)
+intel_engine_using_cmd_parser(const struct intel_engine_cs *engine)
 {
-	return engine->flags & I915_ENGINE_NEEDS_CMD_PARSER;
+	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_REQUIRES_CMD_PARSER;
 }
 
 static inline bool

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -918,7 +918,7 @@ 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;
 }
 
 /**
@@ -930,7 +930,7 @@ 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);
@@ -1317,7 +1317,7 @@ int i915_cmd_parser_get_version(struct drm_i915_private *dev_priv)
 
 	/* If the command parser is not enabled, report 0 - unsupported */
 	for_each_uabi_engine(engine, dev_priv) {
-		if (intel_engine_needs_cmd_parser(engine)) {
+		if (intel_engine_using_cmd_parser(engine)) {
 			active = true;
 			break;
 		}