[SeaBIOS] [Qemu-devel] [PATCH v2 0/3] seabios: add serial console support

Daniel P. Berrange berrange at redhat.com
Tue Jul 5 13:59:37 CEST 2016

On Tue, Jul 05, 2016 at 01:45:10PM +0200, Paolo Bonzini wrote:
> On 05/07/2016 12:07, Daniel P. Berrange wrote:
> >> > What the final default behavior will be is not clear yet.  Not enabled?
> >> > Enabled in case no VGA is present?  Enabled unconditionally (simliar to
> >> > ovmf)?
> > (Bitter) experiance in libvirt has shown us that magically enabling
> > things based on whether or not some other feature is enabled leads
> > to pain and suffering in the long term.
> > 
> > So from libvirt's POV, we would like an explicit command line flag
> > to turn on/off seabios serial console support, with no dependancy
> > on whether VGA is present or not.
> With my other proposal, "-machine graphics=no -device sga" should do it.

Ok, so that combination would just "do the right thing" and use Seabios
built-in serial if available, and fallback to sgabios if not.

> However, for libvirt to do this, it should stop using "-nographic" to
> disable all display backends, and instead use "-display none".  The
> advantage is that neither "-display none" nor "-machine graphics=no" do
> any magic redirection of the monitor and the serial ports to stdio.
> "-display none" is supported since QEMU 1.0.  For old QEMU without
> query-command-line-options it can be scraped from help text; for new
> QEMU with query-command-line-options it can be treated as always there.

Sure, switching to -display none instead of -nographic is no problem
at all.

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