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

[Avi Kivity <avi@redhat.com>]

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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-- 
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