drm/i915: Add support for mandatory cmdparsing

commit 311a50e76a33d1e029563c24b2ff6db0c02b5afe 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>

3 files changed, 12 insertions, 24 deletions

diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index 7fdbbf2f9c2e..bd11913518d4 100644
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -734,7 +734,7 @@ int i915_cmd_parser_init_ring(struct intel_engine_cs *ring)
 		return ret;
 	}
 
-	ring->needs_cmd_parser = true;
+	ring->using_cmd_parser = true;
 
 	return 0;
 }
@@ -748,7 +748,7 @@ int i915_cmd_parser_init_ring(struct intel_engine_cs *ring)
  */
 void i915_cmd_parser_fini_ring(struct intel_engine_cs *ring)
 {
-	if (!ring->needs_cmd_parser)
+	if (!ring->using_cmd_parser)
 		return;
 
 	fini_hash_table(ring);
@@ -914,26 +914,6 @@ unpin_src:
 	return ret ? ERR_PTR(ret) : dst;
 }
 
-/**
- * i915_needs_cmd_parser() - should a given ring use software command parsing?
- * @ring: the ring in question
- *
- * Only certain platforms require software batch buffer command parsing, and
- * only when enabled via module parameter.
- *
- * Return: true if the ring requires software command parsing
- */
-bool i915_needs_cmd_parser(struct intel_engine_cs *ring)
-{
-	if (!ring->needs_cmd_parser)
-		return false;
-
-	if (!USES_PPGTT(ring->dev))
-		return false;
-
-	return (i915.enable_cmd_parser == 1);
-}
-
 static bool check_cmd(const struct intel_engine_cs *ring,
 		      const struct drm_i915_cmd_descriptor *desc,
 		      const u32 *cmd, u32 length,
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 08842e4842a7..137cca662365 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1320,6 +1320,13 @@ eb_get_batch(struct eb_vmas *eb)
 	return vma->obj;
 }
 
+static inline bool use_cmdparser(const struct intel_engine_cs *ring,
+				 u32 batch_len)
+{
+	return ring->requires_cmd_parser ||
+		(ring->using_cmd_parser && batch_len && USES_PPGTT(ring->dev));
+}
+
 static int
 i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		       struct drm_file *file,
@@ -1491,7 +1498,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	}
 
 	params->args_batch_start_offset = args->batch_start_offset;
-	if (i915_needs_cmd_parser(ring) && args->batch_len) {
+	if (use_cmdparser(ring, args->batch_len)) {
 		struct drm_i915_gem_object *parsed_batch_obj;
 
 		parsed_batch_obj = i915_gem_execbuffer_parse(ring,
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 49fa41dc0eb6..56c872b89a92 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -314,7 +314,8 @@ struct  intel_engine_cs {
 		volatile u32 *cpu_page;
 	} scratch;
 
-	bool needs_cmd_parser;
+	bool using_cmd_parser;
+	bool requires_cmd_parser;
 
 	/*
 	 * Table of commands the command parser needs to know about