Re: [Qemu-devel] Why is SeaBIOS used with -kernel?

[Kevin O'Connor]

On Fri, Apr 01, 2016 at 01:07:55PM +0200, Gerd Hoffmann wrote:
> On Fr, 2016-04-01 at 11:17 +0100, Richard W.M. Jones wrote:
> > On Fri, Apr 01, 2016 at 11:18:30AM +0200, Gerd Hoffmann wrote:
> > >   Hi,
> > > 
> > > > I wonder how we can make use of this in qemu and downstream distros?
> > > > Can we have a bios-min.bin which is used with -kernel boots?
> > > 
> > > We already build two seabios roms: one full featued and one slightly
> > > stripped down to keep it below 128k, for backward compatibility with old
> > > machine types.
> > > 
> > > Adding a third config for -kernel boot should be easy.  For that use
> > > case we can probably also turn on seabios logging to the serial console
> > > and drop sgabios.  We don't need input (no boot menu) and we also don't
> > > need to hook into int10 (no grub/ipxe using that for output).
> > 
> > SeaBIOS logging is slow (or more likely, serial output is slow).
> > And sgabios is useful for debugging.
> 
> Ah, I see.  debuglevel=1 prints too much and debuglevel=0 has no logging
> at all.  We'd need seabios log at least the version banner to serial
> even with debuglevel=0 to replace sgabios.

The debug level of messages in SeaBIOS are a bit haphazard today.
I think it would be a good idea to document what types of messages go
in each debug level and then update the current debug messages to fit
that description.  It sounds like level=1 is too verbose today.

-Kevin