[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: <sta...@vger.kernel.org> # v5.6+
Cc: Jason Ekstrand <jason.ekstr...@intel.com>
Cc: Marcin Slusarz <marcin.slus...@intel.com>
Cc: Jon Bloomfield <jon.bloomfi...@intel.com>
Relates: https://gitlab.freedesktop.org/drm/intel/-/issues/3080
Signed-off-by: Daniel Vetter <daniel.vet...@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