[Beignet] [PATCH] intel: Check that we can reserve the zero-offset

[Yang Rong]

commit ff57cee0519d ("ocl20/runtime: take the first 64KB page table
entries") tries to allocate a bo at 0 offset, but failed to take into
account that something may already be allocated there that it is not
allowed to evict (particularly when not using full-ppgtt separation).
Failure to do so causes all execution to subsequentally fail with
"drm_intel_gem_bo_context_exec() failed: Device or resource busy"

Reported-by: Kenneth Johansson <ken at kenjo.org>
Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=98647

Contributor: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Yang Rong <rong.r.yang at intel.com>
---
 src/intel/intel_driver.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/intel/intel_driver.c b/src/intel/intel_driver.c
index b8a1b52..3caf737 100644
--- a/src/intel/intel_driver.c
+++ b/src/intel/intel_driver.c
@@ -137,19 +137,28 @@ return 1;
 static int
 intel_driver_context_init(intel_driver_t *driver)
 {
-driver->ctx = drm_intel_gem_context_create(driver->bufmgr);
-if (!driver->ctx)
-  return 0;
-driver->null_bo = NULL;
+  driver->ctx = drm_intel_gem_context_create(driver->bufmgr);
+  if (!driver->ctx)
+    return 0;
+  driver->null_bo = NULL;
 #ifdef HAS_BO_SET_SOFTPIN
-drm_intel_bo *bo = dri_bo_alloc(driver->bufmgr, "null_bo", 64*1024, 4096);
-drm_intel_bo_set_softpin_offset(bo, 0);
-// don't reuse it, that would make two bo trying to bind to same address,
-// which is un-reasonable.
-drm_intel_bo_disable_reuse(bo);
-driver->null_bo = bo;
+  drm_intel_bo *bo = dri_bo_alloc(driver->bufmgr, "null_bo", 64*1024, 4096);
+  drm_intel_bo_set_softpin_offset(bo, 0);
+  // don't reuse it, that would make two bo trying to bind to same address,
+  // which is un-reasonable.
+  drm_intel_bo_disable_reuse(bo);
+
+  drm_intel_bo_map(bo, 1);
+  *(uint32_t *)bo->virtual = MI_BATCH_BUFFER_END;
+  drm_intel_bo_unmap(bo);
+
+  if (drm_intel_gem_bo_context_exec(bo, driver->ctx, 0, 0) == 0) {
+    driver->null_bo = bo;
+  } else {
+    drm_intel_bo_unreference(bo);
+  }
 #endif
-return 1;
+    return 1;
 }
 
 static void
-- 
2.1.4