VirtIO GPU:
- Removed QEMU 11.x command type swap hack (0x0104↔0x0106).
The hack was wrong — swapping types without swapping data formats
meant handlers read wrong struct layouts. Commands returned OK
but did nothing.
- Restored correct VirtIO spec command types.
- Removed broken test pattern (fill + flush that never displayed).
- GPU setup now reports success/failure without crashing.
Display server resilience:
- VirtioFramebuffer::new() → try_new() -> Option<Self>.
Returns None if phys-info page is unmapped or has zero dimensions.
- bins/display-qemu: tries VirtioFramebuffer, falls back to
MockFramebuffer. Display server runs headless instead of crashing.
- No more page faults when GPU is absent.
The GPU driver code is architecturally correct (proper VirtIO
commands, proper data formats) but doesn't produce visible output
on QEMU 11.x due to a suspected QEMU legacy MMIO bug where
transfer_to_host_2d succeeds but doesn't transfer data. The driver
is ready for when this is fixed or a different QEMU version is used.
Gabriel Kaszewski
25824a01fe