[SeaBIOS] [Qemu-devel] SeaBIOS booting time optimization

Stefano Garzarella sgarzare at redhat.com
Mon Nov 19 11:42:28 CET 2018

On Mon, Nov 19, 2018 at 9:49 AM Gerd Hoffmann <kraxel at redhat.com> wrote:

>   Hi,
> > I'm investigating the SeaBIOS booting time, to understand if we can
> > reduce the boot time in some cases (e.g. legacy hardware is not
> > needed). I think this can be interesting also for NEMU developers.
> > The goal is to have only one image of SeaBIOS configurable at runtime
> > to reduce the boot time, avoiding unnecessary initialization.
> Why at runtime?  What is bad with two images?  With a runtime option
> you probably need some way to enable the "fastboot" hint for seabios,
> because some optimizations (like skipping ps/2 initialization) breaks
> functionality.  So it must be opt-in so you can enable it if you know
> your use case is fine with that.  But "qemu -boot fast=on" isn't much
> different from "qemu -bios seabios-fastboot.bin" after all ...

You are right, but maybe having a single image can be simpler to distribute,
and we can implement something (eg. using fw_cfg) to selectively enable
features needed.
Anyway, as the first step, I'll try to build a separate image of SeaBIOS.

> > Any pointers or suggestions would be helpful.
> seabios could try to skip initializing hardware without bootindex with
> "qemu -boot menu=off,strict=on".
> mmconfig support?  I think that would reduce the number of vmexits
> needed for pci initialization.

Thank you very much, I'll investigate that points.


> cheers,
>   Gerd

Stefano Garzarella
Red Hat
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