On 31/08/2018 12:22, Chris Wilson wrote:
Quoting Lionel Landwerlin (2018-08-31 12:16:19)
We would need a fairly recent kernel (drm-tip?) to test this in CI.
Unpatched mesa, assumes all is fine.
Post-patch mesa, assumes all is broken.
So we can quickly see if anything actually fails if a persistent GGTT
mmap is rejected. Which is the important part for determining if such
exclusion will harm anyone. The problem is then is the risk of
corruption worth keeping it around.
I can't see any issue with this because we always have the meta path as
a fallback for tiled buffers.
I'm worried if the mmap actually leaks through to glMapBufferRange with
say GL_MAP_PERSISTENT_BIT. Hmm, maybe that's all ok so long at the
client flushes are explicit.
As far as I can tell, buffers are linear, so brw_bo_map() wouldn't even
try to map in gtt at first.
Then brw_bo_map_wc() would assert if it failed.
So we're fine? :)
-Chris
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