[libvirt] [PATCH] qemu: Add support for SGA video

[Daniel P. Berrange]

On Mon, Jul 04, 2011 at 03:21:25PM +0200, Michal Privoznik wrote:
> This patch extends possible values for <video> element. Serial Graphics
> Adapter allows users to see BIOS messages from the very first moment
> domain boots up. Therefore, users can choose boot medium, set PXE, etc.

This isn't really the right way todo this. '-sga' is not actually a
new type of video card. It isn't even a guest device. It is just a
hack QEMU uses for loading an option ROM via their qdev infrastructure.
This in turn causes the QEMU BIOS to use a serial port for outputting
messages.

IMHO we should do one of

 - Automatically enable it if no <graphics> is set, but there
   is a <serial> set (ie no XML additions at all)
 - Add a attribute to the <serial> element to allow use of SGA
   to be toggled on/off
 - Add an attribute on the <boot> element to redirect BIOS
   to SGA.

One thing about options 2/3 there is that they could allow
a user to request the BIOS to use the serial port even when
their guest *does* have a <graphics> element present.

Regards,
Daniel
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