Dann, thank you for reply... but is was just my fault.
trying to run manually build OVMF, I used OVMF_VARS.ms.fd from ubuntu stock... and it seems they are different in format.
So when i replaced it with OVMF_VARS.fd generated during build, OVMF started smoothly.
i'm a newbie in this uefi questions...but may be there is must be a check of OVMF_CODE.fd is compatible with OVMF_VARS.fd?
else we see quite undefined behavior at start. - it says kinda - "graphics is not initialized" and hangs.