[PATCH 1/2] drm/i915/cmdparser: No-op failed batches on all platforms

[Daniel Vetter]

On gen9 for blt cmd parser we relied on the magic fence error
propagation which:
- doesn't work on gen7, because there's no scheduler with ringbuffers
  there yet
- fence error propagation can be weaponized to attack other things, so
  not a good design idea

Instead of magic, do the same thing on gen9 as on gen7.

Kudos to Jason for figuring this out.

Fixes: 9e31c1fe45d5 ("drm/i915: Propagate errors on awaiting already signaled fences")
Cc: <stable at vger.kernel.org> # v5.6+
Cc: Jason Ekstrand <jason.ekstrand at intel.com>
Cc: Marcin Slusarz <marcin.slusarz at intel.com>
Cc: Jon Bloomfield <jon.bloomfield at intel.com>
Relates: https://gitlab.freedesktop.org/drm/intel/-/issues/3080
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/i915/i915_cmd_parser.c | 34 +++++++++++++-------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index 5b4b2bd46e7c..2d3336ab7ba3 100644
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -1509,6 +1509,12 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 		}
 	}
 
+	/* Batch unsafe to execute with privileges, cancel! */
+	if (ret) {
+		cmd = page_mask_bits(shadow->obj->mm.mapping);
+		*cmd = MI_BATCH_BUFFER_END;
+	}
+
 	if (trampoline) {
 		/*
 		 * With the trampoline, the shadow is executed twice.
@@ -1524,26 +1530,20 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 		 */
 		*batch_end = MI_BATCH_BUFFER_END;
 
-		if (ret) {
-			/* Batch unsafe to execute with privileges, cancel! */
-			cmd = page_mask_bits(shadow->obj->mm.mapping);
-			*cmd = MI_BATCH_BUFFER_END;
+		/* If batch is unsafe but valid, jump to the original */
+		if (ret == -EACCES) {
+			unsigned int flags;
 
-			/* If batch is unsafe but valid, jump to the original */
-			if (ret == -EACCES) {
-				unsigned int flags;
+			flags = MI_BATCH_NON_SECURE_I965;
+			if (IS_HASWELL(engine->i915))
+				flags = MI_BATCH_NON_SECURE_HSW;
 
-				flags = MI_BATCH_NON_SECURE_I965;
-				if (IS_HASWELL(engine->i915))
-					flags = MI_BATCH_NON_SECURE_HSW;
+			GEM_BUG_ON(!IS_GEN_RANGE(engine->i915, 6, 7));
+			__gen6_emit_bb_start(batch_end,
+					     batch_addr,
+					     flags);
 
-				GEM_BUG_ON(!IS_GEN_RANGE(engine->i915, 6, 7));
-				__gen6_emit_bb_start(batch_end,
-						     batch_addr,
-						     flags);
-
-				ret = 0; /* allow execution */
-			}
+			ret = 0; /* allow execution */
 		}
 	}
 
-- 
2.31.0