multiple allocation for vmcs or am i missing something.

multiple allocation for vmcs or am i missing something.

[Manish Regmi]

When kvm initializes, it calls hardware_setup which calls
alloc_kvm_area which allocates vmcs for each online processor and
stores the pointer in percpu basis.

Later when vmx_create_vcpu is called, the vmcs area is allocated
(again) and this time for the cpu the code is currently executing on.
possibly it is already allocated.

Is this a bug or i am missing something.


-- 
---------------------------------------------------------------
regards
Manish Regmi

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Re: multiple allocation for vmcs or am i missing something.

[Anthony Liguori]

Manish Regmi wrote:
> When kvm initializes, it calls hardware_setup which calls
> alloc_kvm_area which allocates vmcs for each online processor and
> stores the pointer in percpu basis.
>   

VT requires a per-cpu page to store the host state in when VMLAUNCH is 
executed.  This is the host save area and it's passed to the VMXON 
instruction in hardware_enable().  It's the VMCS for the host.

Regards,

Anthony Liguori

> Later when vmx_create_vcpu is called, the vmcs area is allocated
> (again) and this time for the cpu the code is currently executing on.
> possibly it is already allocated.
>
> Is this a bug or i am missing something.
>
>
>   


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Re: multiple allocation for vmcs or am i missing something.

[Guillaume Thouvenin]

On Thu, 8 Feb 2007 21:06:37 +0545
"Manish Regmi" <regmi.manish-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Later when vmx_create_vcpu is called, the vmcs area is allocated
> (again) and this time for the cpu the code is currently executing on.
> possibly it is already allocated.
> 
> Is this a bug or i am missing something.

Hello,

 I don't see where vmx_create_vcpu is called again. I think that it is
called only once from 'r = kvm_arch_ops->vcpu_create(vcpu)'. Thus I don't
think that vmcs area is allocated twice for each vcpu.

Regards,
Guillaume

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Re: multiple allocation for vmcs or am i missing something.

[Manish Regmi]

On 2/9/07, Guillaume Thouvenin <guillaume.thouvenin-6ktuUTfB/bM@public.gmane.org> wrote:
> Hello,
>
>  I don't see where vmx_create_vcpu is called again. I think that it is
> called only once from 'r = kvm_arch_ops->vcpu_create(vcpu)'. Thus I don't
> think that vmcs area is allocated twice for each vcpu.
>
> Regards,
> Guillaume
>
I was was confused when alloc_vmcs_cpu was called twice while
hardware_setup and vmx_create_vcpu.

it is clear to me now.

thanks...

-- 
---------------------------------------------------------------
regards
Manish Regmi

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