systemcalls and kvm ...correct me if I am wrong

systemcalls and kvm ...correct me if I am wrong

[Matteo Signorini]

Hi to all,

correct me if I am wrong but isn't it the following the logical
execution chain of a generic system call performed
in a Kvm guest?

Guest userspace application -> Guest kernel -> Host kernel (kvm) ->
Host userspace (Quemu) -> Host kernel ->
-> Host userspace (Quemu) -> Guest kernel -> Guest userspace application

Is there any detailed documentation on how this happens inside qemu-kvm?

thanks in advance,

Matteo

Re: systemcalls and kvm ...correct me if I am wrong

[Avi Kivity]

Matteo Signorini wrote:
> Hi to all,
>
> correct me if I am wrong but isn't it the following the logical
> execution chain of a generic system call performed
> in a Kvm guest?
>
> Guest userspace application -> Guest kernel -> Host kernel (kvm) ->
> Host userspace (Quemu) -> Host kernel ->
> -> Host userspace (Quemu) -> Guest kernel -> Guest userspace application
>
>   

No.  The actual path is

   guest userspace -> guest kernel -> guest userspace

The guest kernel might access emulated hardware, but usually it does not.

> Is there any detailed documentation on how this happens inside qemu-kvm?
>   

No.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: systemcalls and kvm ...correct me if I am wrong

[Matteo Signorini]

My doubt is:
 will int0x80 from Guest userspace bring me into Guest kernel space or
directly into kvm in the Host kernel?
 How can I trigger a jump from Guest to Host kvm at will?
 Then the way back from host kernel to guest is via vmenter/vmrun or
must be performed in a different way?

thanks in advance,

Matteo

2009/6/7 Avi Kivity <avi@redhat.com>:
> Matteo Signorini wrote:
>>
>> Hi to all,
>>
>> correct me if I am wrong but isn't it the following the logical
>> execution chain of a generic system call performed
>> in a Kvm guest?
>>
>> Guest userspace application -> Guest kernel -> Host kernel (kvm) ->
>> Host userspace (Quemu) -> Host kernel ->
>> -> Host userspace (Quemu) -> Guest kernel -> Guest userspace application
>>
>>
>
> No.  The actual path is
>
>  guest userspace -> guest kernel -> guest userspace
>
> The guest kernel might access emulated hardware, but usually it does not.
>
>> Is there any detailed documentation on how this happens inside qemu-kvm?
>>
>
> No.
>
> --
> Do not meddle in the internals of kernels, for they are subtle and quick to
> panic.
>
>

Re: systemcalls and kvm ...correct me if I am wrong

[Avi Kivity]

Matteo Signorini wrote:
> My doubt is:
>  will int0x80 from Guest userspace bring me into Guest kernel space or
> directly into kvm in the Host kernel?
>   

Like I mentioned, guest kernel.

>  How can I trigger a jump from Guest to Host kvm at will?
>   

mmio/pio/vmcall

>  Then the way back from host kernel to guest is via vmenter/vmrun or
> must be performed in a different way?
>   

The normal way, vmlaunch/vmresume/vmrun.

> thanks in advance,
>
> Matteo
>
> 2009/6/7 Avi Kivity <avi@redhat.com>:
>   
>> Matteo Signorini wrote:
>>     
>>> Hi to all,
>>>
>>> correct me if I am wrong but isn't it the following the logical
>>> execution chain of a generic system call performed
>>> in a Kvm guest?
>>>
>>> Guest userspace application -> Guest kernel -> Host kernel (kvm) ->
>>> Host userspace (Quemu) -> Host kernel ->
>>> -> Host userspace (Quemu) -> Guest kernel -> Guest userspace application
>>>
>>>
>>>       
>> No.  The actual path is
>>
>>  guest userspace -> guest kernel -> guest userspace
>>
>> The guest kernel might access emulated hardware, but usually it does not.
>>
>>     
>>> Is there any detailed documentation on how this happens inside qemu-kvm?
>>>
>>>       
>> No.
>>
>> --
>> Do not meddle in the internals of kernels, for they are subtle and quick to
>> panic.
>>
>>
>>     
> --
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>   


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