[Mesa-dev] [PATCH 1/2] i965: Stop restoring the default L3 configuration on Kernel 4.16+.

[Kenneth Graunke]

Kernel 4.16 has proper context isolation, which means we can change
the L3 configuration without worrying about that leaking to other
newly created contexts, breaking the assumptions of other userspace.

So, disable our workaround to reprogram it back to the default.
---
 src/mesa/drivers/dri/i965/intel_batchbuffer.c | 5 +++--
 src/mesa/drivers/dri/i965/intel_screen.c      | 3 +++
 src/mesa/drivers/dri/i965/intel_screen.h      | 1 +
 3 files changed, 7 insertions(+), 2 deletions(-)

I tested this locally with Piglit and KHR-GLES31.*compute* running
concurrently, on 4.16-rc1.  It seemed to work fine.  I verified that
there were no regressions in the CI, but the CI doesn't run 4.16+, so
I wouldn't expect much to show up there.

diff --git a/src/mesa/drivers/dri/i965/intel_batchbuffer.c b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
index 8a2b4218608..d0999bb3caa 100644
--- a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
+++ b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
@@ -739,9 +739,10 @@ brw_finish_batch(struct brw_context *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.
+       * defaults.  On Kernel 4.16+, we no longer need to do this.
        */
-      if (devinfo->gen >= 7)
+      if (devinfo->gen >= 7 &&
+          !(brw->screen->kernel_features & KERNEL_ALLOWS_CONTEXT_ISOLATION))
          gen7_restore_default_l3_config(brw);
 
       if (devinfo->is_haswell) {
diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
index cc9b3486743..d275b28a4b9 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.c
+++ b/src/mesa/drivers/dri/i965/intel_screen.c
@@ -2654,6 +2654,9 @@ __DRIconfig **intelInitScreen2(__DRIscreen *dri_screen)
    if (devinfo->gen >= 8 || screen->cmd_parser_version >= 5)
       screen->kernel_features |= KERNEL_ALLOWS_COMPUTE_DISPATCH;
 
+   if (intel_get_boolean(screen, I915_PARAM_HAS_CONTEXT_ISOLATION))
+      screen->kernel_features |= KERNEL_ALLOWS_CONTEXT_ISOLATION;
+
    const char *force_msaa = getenv("INTEL_FORCE_MSAA");
    if (force_msaa) {
       screen->winsys_msaa_samples_override =
diff --git a/src/mesa/drivers/dri/i965/intel_screen.h b/src/mesa/drivers/dri/i965/intel_screen.h
index ef2d08974ed..a2bce921449 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.h
+++ b/src/mesa/drivers/dri/i965/intel_screen.h
@@ -81,6 +81,7 @@ struct intel_screen
 #define KERNEL_ALLOWS_COMPUTE_DISPATCH              (1<<4)
 #define KERNEL_ALLOWS_EXEC_CAPTURE                  (1<<5)
 #define KERNEL_ALLOWS_EXEC_BATCH_FIRST              (1<<6)
+#define KERNEL_ALLOWS_CONTEXT_ISOLATION             (1<<7)
 
    struct brw_bufmgr *bufmgr;
 
-- 
2.16.1