"The GEM and DRI2 support in Mesa 7.3 is for Intel
graphics but we should find this level of support coming to the ATI
Radeon DRI driver followed by the Nouveau driver later on for
NVIDIA hardware. To use GEM with Mesa 7.3 you will need a supported
Linux kernel (it was initially merged for the Linux 2.6.28 kernel)
as well as a supported xf86-video-intel driver (such as the latest
2.6 series).
"Regardless of using GEM, a newer version of the Direct
Rendering Manager code is also required (v2.4.3 or later). Some of
the fixes found in Mesa 7.3 include various GL Shading Language bug
fixes, Intel i965 driver fixes, a fix in the WGL/Windows driver,
build fixes for OpenBSD and GCC 2.95, GLSL preprocessor now
handling #pragma, an incorrect transformation of GL_SPOT_DIRECTION,
fixes in glXMakeContextCurrent(), and assorted Windows build
fixes."