[PATCH 3.12 050/122] drm/i915: Only fence tiled region of object.

From: Jiri Slaby
Date: Tue Feb 17 2015 - 06:55:59 EST

From: Bob Paauwe <bob.j.paauwe@xxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


commit af1a7301c7cf8912dca03065d448c4437c5c239f upstream.

When creating a fence for a tiled object, only fence the area that
makes up the actual tiles. The object may be larger than the tiled
area and if we allow those extra addresses to be fenced, they'll
get converted to addresses beyond where the object is mapped. This
opens up the possiblity of writes beyond the end of object.

To prevent this, we adjust the size of the fence to only encompass
the area that makes up the actual tiles. The extra space is considered
un-tiled and now behaves as if it was a linear object.

Testcase: igt/gem_tiled_fence_overflow
Reported-by: Dan Hettena <danh@xxxxxxx>
Signed-off-by: Bob Paauwe <bob.j.paauwe@xxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
drivers/gpu/drm/i915/i915_gem.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7e4e6896fa81..f97d221194a2 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2788,6 +2788,13 @@ static void i965_write_fence_reg(struct drm_device *dev, int reg,
u32 size = i915_gem_obj_ggtt_size(obj);
uint64_t val;

+ /* Adjust fence size to match tiled area */
+ if (obj->tiling_mode != I915_TILING_NONE) {
+ uint32_t row_size = obj->stride *
+ (obj->tiling_mode == I915_TILING_Y ? 32 : 8);
+ size = (size / row_size) * row_size;
+ }
val = (uint64_t)((i915_gem_obj_ggtt_offset(obj) + size - 4096) &
0xfffff000) << 32;
val |= i915_gem_obj_ggtt_offset(obj) & 0xfffff000;

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