[libvirt] How to pass not xml parameters from Libvirt to Xen in xml definition

Alexandre CABROL PERALES alexandre.cabrol at artal.fr
Fri Jul 17 14:30:41 UTC 2009


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CPUID parameters is feature from Xen 3.3 which able to define custom cpu
identification for guest OS in HVM mode.

It's required for Windows NT installation for example.

Or any system which required a specific cpu.

It can be used also to tune performe of physical cpus by guest OS.

This is an example of CPUID usage:

# Intel(R) Pentium(R) 4 CPU

cpuid = [
'0x00000000:eax=0x00000002,ebx=0x756e6547,ecx=0x6c65746e,edx=0x49656e69',

'0x00000001:eax=0x00000f12,ebx=0x00010808,ecx=0x00000000,edx=0x3febfbff',

'0x00000002:eax=0x665b5001,ebx=0x00000000,ecx=0x00000000,edx=0x007a7040',

'0x80000000:eax=0x80000004,ebx=0x00000000,ecx=0x00000000,edx=0x00000000',

'0x80000001:eax=0x00000000,ebx=0x00000000,ecx=0x00000000,edx=0x00000000',

'0x80000002:eax=0x20202020,ebx=0x20202020,ecx=0x20202020,edx=0x6e492020',

'0x80000003:eax=0x286c6574,ebx=0x50202952,ecx=0x69746e65,edx=0x52286d75',

'0x80000004:eax=0x20342029,ebx=0x20555043,ecx=0x30352e31,edx=0x007a4847'
	  ]

It show Identification of Intel Pentium 4 Processor.

This feature is xen specific but usefull and exist in Xen 3.4 and
probably futures too.

Daniel Veillard a écrit :
> On Fri, Jul 17, 2009 at 11:50:35AM +0200, Alexandre CABROL PERALES wrote:
>> Hi everybody,
>> i need to define cpuid parameter for a specific Xen Virtual Machine.
>> This parameters doesn't exist in libvirt definition.
>>
>> So how can i add this "unknow" parameter in virtual machine's xml
>> definition to be able to manage it from virt-manager?
> 
>   There is no such bypass mechanism. If the feature us needed, then
> it need to be recognized and supported at the libvirt API level, in
> order to keep interface coherents and protect from hypervisor specifics
> or changes in said hypervisors.
> 
>   You need to explain why this parameter makes sense at the API level,
> if it is generic enough support will be added (we usually take patches).
> If this is a workaround against a problem or a deficiency in a specific
> version of the hypervisor, the workaround is usually implemented in the
> libvirt driver but not exposed at the API level. The goal is to abstract
> and alleviate problems, not to inflict them permanently.
> 
> Daniel
> 

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Alexandre CABROL PERALES
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