Marvell 88SE9230 passthrough in KVM takes long time to boot

[Konrad Eisele]

      I'm passing through a Marvell 88SE9230 card to a KVM guest under
Ubuntu 18.04. The card is a Sata controller with 4 ports.
The option rom of the Marvell 88SE9230 card shows on a normal boot a
bios screen. When pressing CTRL-m quick enough, you  can interrupt the
bootprocess and enter a menue wherer you can define raid
arrays.

When booting seabios inside KVM the bootprocess is very slow.
There is a 1 min holdtime where the cpu is about 30%. The screen is
black with only the seabios version string shown. I suspect that
the passed-through Marvell 88SE9230 cards option roms causes this
behaviour.
Maybe the scanning for option rom cause the slow bootprocess?

In the seabios boot case no bios menue is shown, after
around 1 min the boot continues.

Is it possible to disable the options rom processing? Is there some
documentation about this (How can I configure it for Ubuntu) ?

// Greetings Konrad