Re: Use host CPUID processor info

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

Dong, Eddie wrote:
> Avi Kivity wrote:
>   
>> One of the uses of virtualization is to abstract the underlying
>> hardware, so that a VM image can run on any platform (live
>> migration is
>> an example of this use case).  For that we must not let any detail of
>> the hardware be visible. 
>>     
>
> I doutb about the live migration cross different architecture. A VM
> using AMD 3DNow can't be migrated to Intel Box. Even within Intel
> processores, A VM using SSE2 can't be migrated to a platform w/o SSE2
> support.
>
> Only if the VM is using the minimal instruction set, minimal features
> may be able to live migrate to other platforms. If this is the purpose,
> probably we can use an ancient processor model for the VM to achieve
> best migration capability in case hybrid processor is adopted. In that
> way we meet both requirement: live migration and app doesn't know it is
> a VM.
>   

It doesn't have to be too ancient.  All virtualization capable 
processors support at least sse2 (and maybe sse3 too).

> Further more, there needs a capibility check for live migration to see
> if it can be migrated to a new platform. If we use host processor model,
> Qemu can simply check both new processor model and required one to see
> if migration can be done, if we use virtual processor model, say qemu
> processor, we have trouble: A vm using qemu processor compiled with SSE2
> can't be migrated to a new platform w/o SSE2 though the capability check
> at migration decision make time says OK (both are qemu processoe). 

No, you only need to check that the host processor is a superset of the 
virtualized processor.

A management solution can also compute a cpuid that is common to all 
machines in the farm and tell qemu to use that via the command line.


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


-------------------------------------------------------------------------
This SF.net email is sponsored by DB2 Express
Download DB2 Express C - the FREE version of DB2 express and take
control of your XML. No limits. Just data. Click to get it now.
http://sourceforge.net/powerbar/db2/