Re: exception 12

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Andreas Hasenack wrote:
> On Tuesday 20 February 2007 13:54:53 Avi Kivity wrote:
>   
>> Andreas Hasenack wrote:
>>     
>>> kernel 2.6.20 vanilla
>>> kvm 14 kernel modules and userspace + "qemu kvm target" patch
>>> everything built with gcc 4
>>>
>>> Is this supposed to work? The vdisk.img was created with qemu-img
>>> following the howto (http://kvm.qumranet.com/kvmwiki/HOWTO). I don't have
>>> the iso for a boot image, so inserted an ubuntu 6.06 alternate install cd
>>> in the drive (/dev/cdrom).
>>>       
>> This looks like another case of missing real mode emulation on Intel
>> hosts.  If you have access to an AMD machine with svm support, you might
>>     
>
> Is this a shortcoming in the Intel implementation? Something serious, i.e., is 
> Intel just "playing" with virtualization while AMD has it done correctly?
>
>
>   

The AMD virtualization support makes it fairly easy to support real 
mode.  The Intel implementation requires significant virtual machine 
monitor support for proper real mode.

Real mode has no impact on performance, only on the boot stages.  It's 
certainly incorrect to say Intel is only "playing" with virtualization; 
it's just a design choice of an obscure feature.  But in this particular 
area, Intel has made life hard on VMM developers.

There are other things that are much simpler on the AMD implementation; 
it's generally easier to work with.  Since they've arrived later on the 
scene, they can learn from Intel's mistakes.

Having said all that, the missing real mode support is a kvm bug, not an 
Intel one.  We have to work with whatever the hardware provides and 
supply what it doesn't.

-- 
error compiling committee.c: too many arguments to function


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