Re: Real Mode Improvement on Intel Hosts - GSoC Project

[Anthony Liguori <anthony@codemonkey.ws>]

Mohammed Gamal wrote:
> Hi,
> My Project proposal "Improving and Stabilizing Real-Mode Support for
> Intel Hosts" has been accepted into Google Summer of Code under the
> Linux Foundation. You may have a look at  the proposal abstract here:
> http://code.google.com/soc/2008/linux/appinfo.html?csaid=1CC1C8B4CCC1120E
> .
>
> Any pointers on where to start, what would you like to see done, and
> any other comments and suggestions would greatly be appreciated.
>   

We have a two stage plan to address real-mode on Intel systems.  Both 
involve using x86_emulate() to emulate 16-bit (and 32-bit) instructions 
that VT cannot handle.

The first stage is to detect vmentry failures and run x86_emulate() for 
a single instruction.  If you look at the mailing list, you'll see 
patches from myself and Guillaume.  This should be enough to allow most 
Ubuntu installer CDs to work under KVM.  In this case, the CDs are using 
a version of GFXBOOT that doesn't use big real mode, but still relies on 
an undefined architectural aspect that VT doesn't support.

The second stage is to use a loop of x86_emulate() to run all 16-bit 
code (instead of using vm86 mode).  This will allow us to support guests 
that use big real mode.

The best place to start is probably to try out some of the patches on 
the list, and get familiar with the GFXBOOT assembly routines.  There's 
a #kvm in FreeNode, that's a good place to start if you're having 
trouble getting started.

Regards,

Anthony Liguori

> Regards,
> Mohammed
>
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