Neverball: L8A8 swapped, 1-pixel mipmap levels, and graph exception 0x105 (2026-10-16)

Symptom. Neverball was the first game to show three driver bugs in one day: its fonts and HUD drew with wrong alpha, its non-square textures broke the GPU’s mipmap generation, and on Mesa ps3.223 it wedged the RSX with a graph exception (batch 2026-10-16-mesa-223-neverball-wedge: nouveau: kernel rejected pushbuf, 89 lines and 35 000 dump lines, ps3rsx: graph exception).

Evidence and cause. Each was reduced to a test in ps3-gpu-tools’ mesa-tests:

• gl-texfmt: GL_LUMINANCE_ALPHA (L8A8) textures were sampled with L and A swapped (batch 2026-10-16-mesa-186-checks). Fonts in many games use it.
• gl-genmip: GPU mipmap generation of non-square textures: the 1-pixel levels are swizzled render targets the ps3rsx validator refuses, so the push was lost (rejected push: swizzled render target 1 pixel wide). SuperTuxKart and Luanti hit it too.
• 0x105: nv30’s 3D blit sampled a mip level at an offset not 128-byte aligned: Mesa’s CPU mipmap generation reading back the 2x2 level of a 32x32 L8A8 texture. Any game generating mipmaps for L8A8, L8, A8, I8, 4444 or 5551 could hit it.

Fix. Mesa 0012 (L8A8) and 0013 (genmip) in ps3.223 (batch 2026-10-16-mesa-223-checks); Mesa 0014 in ps3.225, with gl-mipread passing all 70 cases (batch 2026-10-16-mesa-225); ps3rsx 0.249 refuses texture offsets that are not 128-byte aligned (8e99b76), so a bad blit is refused instead of wedging the GPU. No wedge in the Neverball runs since. The mechanisms are in DRIVER.md and RSX.md.