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Re: Compatibility between -device sga and -machine graphics=off
From: |
Daniel P . Berrangé |
Subject: |
Re: Compatibility between -device sga and -machine graphics=off |
Date: |
Wed, 8 Sep 2021 17:36:29 +0100 |
User-agent: |
Mutt/2.0.7 (2021-05-04) |
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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