We observed that Venus on ANV on JSL platform has some cacheline flush
issue. The overflush shows up as:
1. There're 2 threads venus bliting the feedback buffers suballocated
from the same backing device memory, back to back.
2. On thread A, flushing the feedback buffer for cpu read is placed
behind flushing a shader storage buffer for cpu read.
3. On thread B, flushing a different feedback buffer with the same
backing device memory (different offset bound to) can kick the
feedback buffer flush in (2) earlier than it should be flushed.
4. As a result, CPU polling thread for thread B results would see venus
feedback buffer update earlier than shader storage buffer results
being updated, breaking Venus sync primitives optimization.
During investigation, a solid workaround for JSL platform is to force
Venus to align up to 128 bytes for feedback buffer suballocation while
the default is at 64 bytes.
Cc: mesa-stable
Signed-off-by: Yiwei Zhang <zzyiwei@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30879>
Yiwei Zhang
7941d705c3