Pulling in fix for bug #140713 for Gutsy release

Matt Zimmerman mdz at ubuntu.com
Fri Oct 12 10:09:56 BST 2007


It's up to the release managers whether this is worthwhile, though with
gfxboot being such a critical and hardware-dependent component, making a
change like this seems awfully risky at the 11th hour.  It simply can't be
properly tested at this point.

On Thu, Oct 11, 2007 at 09:52:02AM -0500, Anthony Liguori wrote:
> Due to real mode usage in gfxboot, Ubuntu has never been able to install    
>  under KVM or Xen on Intel (VT) processors.  The latest version of gfxboot 
> attempted to fix this problem but there is a bug.
>
> A one-line fix is available that fixes the problem and allows Gutsy to be 
> installed under KVM or Xen.  The fix came from the gfxboot maintainer 
> (Steffen Winterfeldt) and has gotten a lot of review on kvm-devel.
>
> While it is rather late to apply such a fix, the reward is great (allowing 
> Gutsy to be used for open virtualization on Intel) and the risk is low 
> since the patch has gotten a lot of review and is pretty obvious.
>
> I've included the patch in this email but the bug report should be 
> consulted for more information around the patch.
>
> Sorry if this is the wrong place for such a request, I'm not that familiar 
> with how things work in Ubuntu.  The bug hasn't gotten much attention on 
> launchpad and it's very important this is taken before the release of Gutsy 
> (or it won't be useful until Gutsy+1).
>
> https://bugs.launchpad.net/ubuntu/+source/gfxboot/+bug/140713
>
> Regards,
>
> Anthony Liguori

> --- a/bincode.asm	2007-07-24 05:49:46.000000000 -0500
> +++ b/bincode.asm	2007-10-11 09:18:57.000000000 -0500
> @@ -15546,7 +15546,11 @@
>  		mov ax,pm_seg.prog_d16
>  		mov ds,ax
>  
> -		mov eax,ss
> +		; needed for KVM:
> +		; ss:rpl must equal cs:rpl in PM for VT. We can't rely on ss
> +		; maintaining its value after the transition.
> +
> +		movzx eax,word [rm_seg.ss]
>  		and esp,0ffffh
>  		shl eax,4
>  		add esp,eax

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-- 
 - mdz



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