[Mesa-dev] [PATCH] i965: Fix GLX_MESA_query_renderer video memory on 32-bit.

[Kenneth Graunke]

On modern systems with 4GB apertures, the size in bytes is 4294967296,
or (1ull << 32).  The kernel gives us the aperture size as a __u64,
which works out great.

Unfortunately, libdrm "helpfully" returns the data as a size_t, which
on 32-bit systems means it truncates the aperture size to 0 bytes.
We've happily reported this value as 0 MB of video memory via
GLX_MESA_query_renderer since it was originally exposed.

This patch bypasses libdrm and calls the ioctl ourselves so we can
use a proper uint64_t, avoiding the 32-bit integer overflow.  We now
report a proper video memory size on 32-bit systems.
---
 src/mesa/drivers/dri/i965/intel_screen.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
index 811a9c5a867..f94e8a77c10 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.c
+++ b/src/mesa/drivers/dri/i965/intel_screen.c
@@ -950,6 +950,17 @@ static const __DRIimageExtension intelImageExtension = {
     .createImageWithModifiers           = intel_create_image_with_modifiers,
 };
 
+static uint64_t
+get_aperture_size(int fd)
+{
+   struct drm_i915_gem_get_aperture aperture;
+
+   if (drmIoctl(fd, DRM_IOCTL_I915_GEM_GET_APERTURE, &aperture) != 0)
+      return 0;
+
+   return aperture.aper_size;
+}
+
 static int
 brw_query_renderer_integer(__DRIscreen *dri_screen,
                            int param, unsigned int *value)
@@ -972,10 +983,7 @@ brw_query_renderer_integer(__DRIscreen *dri_screen,
        * assume that there's some fragmentation, and we start doing extra
        * flushing, etc.  That's the big cliff apps will care about.
        */
-      size_t aper_size;
-      size_t mappable_size;
-
-      drm_intel_get_aperture_sizes(dri_screen->fd, &mappable_size, &aper_size);
+      uint64_t aper_size = get_aperture_size(dri_screen->fd);
 
       const unsigned gpu_mappable_megabytes =
          (aper_size / (1024 * 1024)) * 3 / 4;
-- 
2.12.1