Comment 3 for bug 356381

The actual problem is this: the i915 drm-driver feeds pages allocated using kcalloc into the agp subsystem. On systems having more than 3G of RAM, these pages may have physical addresses beyond the 4GB boundary, thus being unreachable for the (current?) agp implementation. On its way into the agp subsystem, the extra bits are chopped off, and if the GPU writes anything in that space, it is probably overwriting kernel memory. If i find out how to allocate memory in the low 4GB, a patch will follow.