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

[Paolo Bonzini <pbonzini@redhat.com>]

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.

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.

Paolo