Re: Compatibility between -device sga and -machine graphics=off

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Sep 08, 2021 at 06:28:01PM +0200, Paolo Bonzini wrote:
> On 08/09/21 18:08, Daniel P. Berrangé wrote:
> > Despite this difference, I was able migrate from a x86 guest using SGA
> > to a guest using graphics=off without errors being reported. So it
> > doesn't seem to change the migration data sections sent on the wire
> > at least.
> 
> It would probably break with Windows XP/2003 guests on AMD processors, as
> those are the ones that use kvmvapic.  On other guests and processors, it's
> a no-op.

After running an incoming migrate, the target QEMU's  'info mtree'
changed to reflect what the src QEMU originally reported.  So whatever
difference 'graphics=off' causes compared to -device sga initially,
appears to have been eliminated by running the migrate. Not sure if
that's true in the general case or not - I'm just testing with a
minimalist CLI and no real OS running

 qemu-system-x86_64 -nodefaults -display sdl -device VGA -serial stdio  -device sga

vs

 qemu-system-x86_64 -nodefaults -display sdl -device VGA -serial stdio  -machine graphics=off

Regards,
Daniel
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