[Intel-gfx] [PATCH] drm/i915: Handle request to map a very large buffer object

[Anuj Phogat]

This patch sets an upper limit on the size of buffer object which can be
mapped safely. Following bugs reported segmentation fault / assertion
failure with large textures:

https://bugs.freedesktop.org/show_bug.cgi?id=44970
https://bugs.freedesktop.org/show_bug.cgi?id=46303

This patch along with another patch which I posted on mesa-dev
(intel: Fix a case when mapping large texture fails) resolve
above mentioned bugs. Recently posted piglit test case (large-textures)
also passes with these patches.

Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
---
This fix doesn't limit developers to create very large texture but it
restricts them to map it. I am not very confident about this patch and
setting 128 MB as the upper limit on size of buffer object. So, please
provide your views.

Chris Wilson's views on this issue:
http://www.mail-archive.com/intel-gfx@lists.freedesktop.org/msg08585.html

 intel/intel_bufmgr_gem.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/intel/intel_bufmgr_gem.c b/intel/intel_bufmgr_gem.c
index 0f33b71..8b05de9 100644
--- a/intel/intel_bufmgr_gem.c
+++ b/intel/intel_bufmgr_gem.c
@@ -1191,6 +1191,17 @@ int drm_intel_gem_bo_map_gtt(drm_intel_bo *bo)
 
 	pthread_mutex_lock(&bufmgr_gem->lock);
 
+	/* Set am upper limit on the size of buffer which can be mapped
+	   safely
+	 */
+	if (bo->size > 128 * 1024 * 1024) {
+		DBG("%s:%d: Reached buffer map limit.\n",
+		    __FILE__, __LINE__);
+		bo->virtual = NULL;
+		pthread_mutex_unlock(&bufmgr_gem->lock);
+		return -1;
+	}
+
 	if (bo_gem->map_count++ == 0)
 		drm_intel_gem_bo_open_vma(bufmgr_gem, bo_gem);
 
-- 
1.7.7.6