[Qemu-devel] Re: [kvm-devel] [PATCH] [RFC] try to reduce kvm impact in core qemu code.

[Glauber Costa <gcosta@redhat.com>]

Anthony Liguori wrote:
> Glauber Costa wrote:
>> Avi Kivity wrote:
>>  
>>> Glauber Costa wrote:
>>>    
>>>> Hi. This is a proposal for reducing the impact of kvm functions in 
>>>> core qemu
>>>> code. This is by all means not ready, but I felt like posting it, so 
>>>> a discussion
>>>> on it could follow.
>>>>
>>>> The idea in this patch is to replace the specific kvm details from 
>>>> core qemu files
>>>> like vl.c, with driver_yyy() functions. When kvm is not running, 
>>>> those functions would
>>>> just return (most of time), absolutely reducing the impact of kvm code.
>>>>
>>>> As I wanted to test it, in this patch I changed the kvm functions to 
>>>> be called driver_yyy(),
>>>> but that's not my final goal. I intend to use a function pointer 
>>>> schema, similar to what the linux
>>>> kernel already do for a lot of its subsystem, to isolate the changes.
>>>>
>>>> Comments deeply welcome.
>>>>         
>>> While I would be very annoyed if someone referred to kvm as a qemu 
>>> accelerator, I think accelerator_yyy() is more descriptive than 
>>> driver_yyy().
>>>     
>> How about booster? ;-)
>>   
> 
> I don't think the concern from a QEMU perspective is that QEMU is too 
> intimately tied to KVM.  The concern is that overtime, it will be very 
> difficult to make changes to QEMU without breaking KVM support because 
> of the shear number of hooks we require.  Fabrice had actually suggested 
> merging libkvm into QEMU.  We just need to reduce the overall number of 
> if (kvm_enabled()) blocks.

They are not mutually exclusive. Even if we do merge libkvm into qemu, 
having it more modular and separated will be way better than having kvm 
hooks all over.