VMXON region vs VMCS region?

VMXON region vs VMCS region?

[Zhi Yong Wu]

HI,

Can anyone let me know know the difference  between VMXON region and
VMCS region? relationship?

It will be appreciated if you can make some comments.


-- 
Regards,

Zhi Yong Wu

Re: VMXON region vs VMCS region?

[Orit Wasserman]

On 01/31/2012 05:35 AM, Zhi Yong Wu wrote:
> HI,
> 
> Can anyone let me know know the difference  between VMXON region and
> VMCS region? relationship?
> 

There is no relationship between them:
VMXON region is created per logical processor and used by it for VMX ops.
VMCS region is created for each guest vcpu and used both by the hypervisor and the processor.

> It will be appreciated if you can make some comments.
> 
> 

Re: VMXON region vs VMCS region?

[Zhi Yong Wu]

On Tue, Jan 31, 2012 at 8:29 PM, Orit Wasserman <owasserm@redhat.com> wrote:
> On 01/31/2012 05:35 AM, Zhi Yong Wu wrote:
>> HI,
>>
>> Can anyone let me know know the difference  between VMXON region and
>> VMCS region? relationship?
>>
>
> There is no relationship between them:
> VMXON region is created per logical processor and used by it for VMX ops.
> VMCS region is created for each guest vcpu and used both by the hypervisor and the processor.
Great, thanks.
>
>> It will be appreciated if you can make some comments.
>>
>>
>



-- 
Regards,

Zhi Yong Wu

Re: VMXON region vs VMCS region?

[Zhi Yong Wu]

On Tue, Jan 31, 2012 at 8:29 PM, Orit Wasserman <owasserm@redhat.com> wrote:
> On 01/31/2012 05:35 AM, Zhi Yong Wu wrote:
>> HI,
>>
>> Can anyone let me know know the difference  between VMXON region and
>> VMCS region? relationship?
>>
>
> There is no relationship between them:
> VMXON region is created per logical processor and used by it for VMX ops.
VMXON is created per VMM, not per logical processor, right?

Intel spec says as below:

Before entering VMX operation, the host VMM allocates a VMXON region. A VMM can
host several virtual machines and have many VMCSs active under its management.
A unique VMCS region is required for each virtual machine; a VMXON region is
^^^ if each vm has multiple logical processor, A unique VMCS region is
required for each logical processor.
required for the VMM itself.

> VMCS region is created for each guest vcpu and used both by the hypervisor and the processor.
I suddently have one question about logical processor and guest vcpu.
What is their relationship?

>
>> It will be appreciated if you can make some comments.
>>
>>
>



-- 
Regards,

Zhi Yong Wu

Re: VMXON region vs VMCS region?

[Zhi Yong Wu]

On Wed, Feb 8, 2012 at 1:52 AM, Orit Wasserman <owasserm@redhat.com> wrote:
> On 02/07/2012 05:09 PM, Zhi Yong Wu wrote:
>> On Tue, Jan 31, 2012 at 8:29 PM, Orit Wasserman <owasserm@redhat.com> wrote:
>>> On 01/31/2012 05:35 AM, Zhi Yong Wu wrote:
>>>> HI,
>>>>
>>>> Can anyone let me know know the difference  between VMXON region and
>>>> VMCS region? relationship?
>>>>
>>>
>>> There is no relationship between them:
>>> VMXON region is created per logical processor and used by it for VMX ops.
>> VMXON is created per VMM, not per logical processor, right?
> Not exactly ,it is per logical processor the only thing that it contain that can effect the VMM is the VMCS version.
> you can't do VMXON twice on the same logical processor (it will fail).
> For example if kvm is run in non exclusive mode it will will vmxon/vmxoff before/after running the guest
ah, this case is for nested KVM
> (I think vmware does it too). In exclusive mode it does VMXON when the kvm module is loaded and VMOFF when it is removed, no other VMM can use VMX on that logical processor.
> So in theory, one VMM can do the VMXON and the other can just use VMX without doing VMXON but it has to use the same VMCS version (there are changes to the VMCS structure in different versions).
very wonderful, thanks.
>
>>
>> Intel spec says as below:
>>
>> Before entering VMX operation, the host VMM allocates a VMXON region. A VMM can
>> host several virtual machines and have many VMCSs active under its management.
>> A unique VMCS region is required for each virtual machine; a VMXON region is
>> ^^^ if each vm has multiple logical processor, A unique VMCS region is
>> required for each logical processor.
>> required for the VMM itself.
>
>>
>>> VMCS region is created for each guest vcpu and used both by the hypervisor and the processor.
>> I suddently have one question about logical processor and guest vcpu.
>> What is their relationship?
>>
>>>
>>>> It will be appreciated if you can make some comments.
>>>>
>>>>
>>>
>>
>>
>>
>



-- 
Regards,

Zhi Yong Wu