This field encodes bits [27:6] of the scratch surface state offset
according to the hardware spec, already on XeHP platforms. However,
on previous platforms we were passing bits [25:4] instead, which was
apparently okay for two reasons:
1/ We never used more than 8 MB of scratch surface states apparently.
2/ A shift right by 2 was implicitly happening while copying the
value of r0.5 into the address register holding the extended
descriptor, which with the ExBSO addressing mode disabled
considered bits [31:12] as the surface state index within the
pool.
However on Xe2 ExBSO addressing mode is always enabled for the UGM
shared function, so we have to add an extra SHR instruction to format
the extended descriptor regardless, and there is no point in
disobeying the hardware spec passing a left-shifted offset.
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29543>
Francisco Jerez
8bbad903a2