There is no 3d support for Via, so you can only get software. If llvm has trouble with your application, you can fall back on softpipe by using the GALLIUM_DRIVER=softpipe variable. E. g.
GALLIUM_DRIVER=softpipe myapp
Be warned that both software drivers are too slow to run any games, and most non-game GL apps. Barely can run a 3d screensaver at good fps, and that is on a recent Intel cpu, on a Via chipset you'll have an older cpu.