i965: Work around L3 state leaks during context switches.

This is going to require some rather intrusive kernel changes to fix
properly, in the meantime (and forever on at least pre-v4.1 kernels)
we'll have to restore the hardware defaults at the end of every batch
in which the L3 configuration was changed to avoid interfering with
the DDX and GL clients that use an older non-L3-aware version of Mesa.

Reviewed-by: Samuel Iglesias Gonsálvez <[email protected]>
Reviewed-by: Kristian Høgsberg  <[email protected]>

v2: Optimize look-up of the default configuration by assuming it's the
    first entry of the L3 config array in order to avoid an FPS
    regression in GpuTest Triangle and SynMark OglBatch2-7 on most
    affected platforms.

Reviewed-by: Jordan Justen <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/intel_batchbuffer.c b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
index 0363bd3789a..f77807472fd 100644
--- a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
+++ b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
@@ -208,6 +208,13 @@ brw_finish_batch(struct brw_context *brw)
    brw_emit_query_end(brw);
 
    if (brw->batch.ring == RENDER_RING) {
+      /* Work around L3 state leaks into contexts set MI_RESTORE_INHIBIT which
+       * assume that the L3 cache is configured according to the hardware
+       * defaults.
+       */
+      if (brw->gen >= 7)
+         gen7_restore_default_l3_config(brw);
+
       /* We may also need to snapshot and disable OA counters. */
       brw_perf_monitor_finish_batch(brw);