Re: xen 3.0 for AMD Pacifica

[Anthony Liguori <aliguori@us.ibm.com>]

Dave Feustel wrote:

>On Tuesday 25 October 2005 09:53, Anthony Liguori wrote:
>  
>
>>Dave Feustel wrote:
>>
>>    
>>
>>>>We intend to add support for x86 h/w virtualization extensions 
>>>>as information about them becomes available.
>>>>   
>>>>
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>>>>
>>>What information is needed beyond the Pacifica documentation already
>>>provided by AMD and the Vanderpool docs provided by Intel?
>>> 
>>>
>>>      
>>>
>>I don't know where you're quoting from, but both specs are out publicly.
>>    
>>
>
>I know. I have both. What I was asking is whether the info in those documents
>is sufficient to make Xen work with  the hardware of both chips, or is additional 
>info needed (and still not available)?
>
Sorry, then yes, theoritically, all you should need are those specs.

>>Both VT and Pacifica are pretty similiar in the basic idea that they 
>>allow the processor to be put in a mode where 30 or so events that 
>>normally don't trap actually do trap.
>>    
>>
>
>Pacifica has a new paging mode (paged real mode) made possible by the 
>Opteron on-chip memory controller. This feature is not present in VT.
>  
>
Yes, there are considerable differences.  Pacifica has paged real mode 
whereas VT requires vm86 mode to be used for real mode emulation.  
Pacifica also has (optional) support for hardware shadow page tables, 
TLB tagging, and DMA memory protection.  They also have different models 
for dealing with the VMCS/VMCB.  I would categorize this stuff mostly as 
optimizations though since none of it's required to meet the 
Popek/Goldberg requirements.

Just enough differences to make things interesting :-)

Regards,

Anthony Liguori

>>Just having the processor trap though doesn't get you virtualization 
>>:-)  Each of those events has to be handled, and often emulated.  Throw 
>>in shadow paging and IO emulation and it's all rather complicated.
>>
>>Plus, there's not much that can be done without having the hardware at 
>>this point.
>>
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>>>Is there any possibility of setting up a mailing list directed specifically at
>>>xen 3.0 hardware supported virtualization?
>>> 
>>>
>>>      
>>>
>>There are an awful lot of Xen mailing lists at this point.  What would 
>>be *really* useful is having some content on the wiki that went into 
>>more depth about VT/Pacifica.
>>
>>Regards,
>>
>>Anthony Liguori
>>
>>    
>>
>>>Thanks,
>>>Dave Feustel
>>>
>>>
>>> 
>>>
>>>      
>>>
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>>
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