[Mesa-dev] [PATCH] i965: Embrace "unlimited" GTT mmap support

[Chris Wilson]

>From about kernel 4.9, GTT mmaps are virtually unlimited. A new
parameter, I915_PARAM_MMAP_GTT_VERSION, is added to advertise the
feature so query it and use it to avoid limiting tiled allocations to
only fit within the mappable aperture.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_context.c  | 17 ++---------------
 src/mesa/drivers/dri/i965/brw_context.h  |  2 +-
 src/mesa/drivers/dri/i965/intel_screen.c | 32 ++++++++++++++++++++++++++++++++
 src/mesa/drivers/dri/i965/intel_screen.h |  2 ++
 4 files changed, 37 insertions(+), 16 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index b0f9063..79dba1e 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -1033,21 +1033,6 @@ brwCreateContext(gl_api api,
    brw->urb.max_ds_entries = devinfo->urb.max_ds_entries;
    brw->urb.max_gs_entries = devinfo->urb.max_gs_entries;
 
-   /* Estimate the size of the mappable aperture into the GTT.  There's an
-    * ioctl to get the whole GTT size, but not one to get the mappable subset.
-    * It turns out it's basically always 256MB, though some ancient hardware
-    * was smaller.
-    */
-   uint32_t gtt_size = 256 * 1024 * 1024;
-
-   /* We don't want to map two objects such that a memcpy between them would
-    * just fault one mapping in and then the other over and over forever.  So
-    * we would need to divide the GTT size by 2.  Additionally, some GTT is
-    * taken up by things like the framebuffer and the ringbuffer and such, so
-    * be more conservative.
-    */
-   brw->max_gtt_map_object_size = gtt_size / 4;
-
    if (brw->gen == 6)
       brw->urb.gs_present = false;
 
@@ -1058,6 +1043,8 @@ brwCreateContext(gl_api api,
 
    brw->predicate.state = BRW_PREDICATE_STATE_RENDER;
 
+   brw->max_gtt_map_object_size = screen->max_gtt_map_object_size;
+
    brw->use_resource_streamer = screen->has_resource_streamer &&
       (env_var_as_boolean("INTEL_USE_HW_BT", false) ||
        env_var_as_boolean("INTEL_USE_GATHER", false));
diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index f2dd164..523f36c 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -861,7 +861,7 @@ struct brw_context
     */
    bool perf_debug;
 
-   uint32_t max_gtt_map_object_size;
+   uint64_t max_gtt_map_object_size;
 
    int gen;
    int gt;
diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
index 98f1c76..62eacba 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.c
+++ b/src/mesa/drivers/dri/i965/intel_screen.c
@@ -1006,6 +1006,17 @@ intel_get_boolean(struct intel_screen *screen, int param)
    return (intel_get_param(screen, param, &value) == 0) && value;
 }
 
+static int
+intel_get_integer(struct intel_screen *screen, int param)
+{
+   int value = -1;
+
+   if (intel_get_param(screen, param, &value) == 0)
+	   return value;
+
+   return -1;
+}
+
 static void
 intelDestroyScreen(__DRIscreen * sPriv)
 {
@@ -1576,6 +1587,27 @@ __DRIconfig **intelInitScreen2(__DRIscreen *psp)
    if (INTEL_DEBUG & DEBUG_AUB)
       drm_intel_bufmgr_gem_set_aub_dump(intelScreen->bufmgr, true);
 
+#define I915_PARAM_MMAP_GTT_VERSION 40 /* XXX delete me with new libdrm */
+   if (intel_get_integer(intelScreen, I915_PARAM_MMAP_GTT_VERSION) >= 1) {
+      /* Theorectically unlimited! */
+      intelScreen->max_gtt_map_object_size = UINT64_MAX;
+   } else {
+      /* Estimate the size of the mappable aperture into the GTT.  There's an
+       * ioctl to get the whole GTT size, but not one to get the mappable subset.
+       * It turns out it's basically always 256MB, though some ancient hardware
+       * was smaller.
+       */
+      uint32_t gtt_size = 256 * 1024 * 1024;
+
+      /* We don't want to map two objects such that a memcpy between them would
+       * just fault one mapping in and then the other over and over forever.  So
+       * we would need to divide the GTT size by 2.  Additionally, some GTT is
+       * taken up by things like the framebuffer and the ringbuffer and such, so
+       * be more conservative.
+       */
+      intelScreen->max_gtt_map_object_size = gtt_size / 4;
+   }
+
    intelScreen->hw_has_swizzling = intel_detect_swizzling(intelScreen);
    intelScreen->hw_has_timestamp = intel_detect_timestamp(intelScreen);
 
diff --git a/src/mesa/drivers/dri/i965/intel_screen.h b/src/mesa/drivers/dri/i965/intel_screen.h
index 35cd5df..fa806a3 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.h
+++ b/src/mesa/drivers/dri/i965/intel_screen.h
@@ -44,6 +44,8 @@ struct intel_screen
 
    __DRIscreen *driScrnPriv;
 
+   uint64_t max_gtt_map_object_size;
+
    bool no_hw;
    bool hw_has_swizzling;
    bool has_fence_fd;
-- 
2.9.3