I’m surprised you didn’t use your shiny exploit to get enough access to write a startup script or give yourself root. Or patch the driver :)

(I’ve had Astra suggest binary patches things when I don’t even ask it to.)

re: the DMA API, it’s been a while since I’ve poked at it (and I’ve only really poked seriously on x86 Xen PV), but I think there are explicit APIs for cache maintenance, and you drivers may also be able to ask for more coherent mappings depending on hardware. You’re certainly not expected to stick arch-specific flush operations in.