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