With Mesa 20.1 even after the kernel change to do wbinvd on all cpus
sthen@ reported that hard hangs still occurred on his Haswell system
with inteldrm.
Mark Kane also reported seeing hangs on Ivy Bridge on bugs@.
Some systems/workloads seem to be more prone to triggering this than
others as I have not seen any hangs on Ivy Bridge and the only hangs
I saw on Haswell when running piglit went away with the wbinvd change.
It seems something is wrong with drm memory attributes or coherency in
the kernel and newer Mesa versions expect behaviour we don't have.
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