How to access VRAM physical address on L4 ?

Dear:

Question: How to access VRAM physical address on L4 ?

We are implementing a multi server OS on L4.
QEMU and VMware are used for OS run-test.

We are now considering to develope a simple VGA driver
for QEMU (using -stdvga mode).

QEMU (-stdvga option) allows us to set the VRAM area
at physical address 0xe0000000.

Sigma0 do not know this VRAM area, and we cannot
ask sigma0 to map it to a process.
We wonder how to access the physical VRAM area
from the L4 user-mode process.

Thanks in advance.
---
K. Maruyama