Re: [Qemu-devel] -vga std vs. -device VGA

[Alexander Graf]

Am 14.11.2013 um 20:25 schrieb Alexey Kardashevskiy <address@hidden>:

> On 11/15/2013 10:03 AM, Peter Maydell wrote:
>> On 14 November 2013 22:32, Benjamin Herrenschmidt
>> <address@hidden> wrote:
>>> On Thu, 2013-11-14 at 17:23 -0500, Alexander Graf wrote:
>>>> Yes. But I think it's the correct thing to do in this case. X86 also
>>>> doesn't create a USB controller like we would have to. Our pseries
>>>> platform just doesn't have a legacy PC/AT keyboard controller.
>>> 
>>> Sure, but that implies that -nodefaults -device VGA creates a working
>>> usable machine on x86 and not on pseries...
>> 
>> Sounds plausible. Anything using -nodefaults has to have
>> knowledge of every QEMU machine type it wants to use
>> so it can know which devices need adding in order to get
>> various functionality. ('-device VGA' doesn't work at all on
>> some, for instance). If you ask for full manual control, you
>> get full manual control :-)
> 
> That is ok and I asked our libvirt person to fix it (Hi Li :) ).
> 
> What I still do not completely understand is the principle used about
> automatic device creation. Specifically, "-device VGA" creates only VGA
> (and that is understandable) but "-vga std" creates more devices, if if
> used together with "-nodefaults".
> 
> Is it because "-device" must create only what it is told to create and
> others non-"-device" options (-usb? -vga? -machine ...? any!) can
> auto-create whatever they want (well, what seems reasonable to create for
> the specific arch)?

Yeah, you can use QEMU as the interface to the user, then you want to be easy 
and smart. Or you can use QEMU as interface to a management stack. Then you 
want to be as precise and deterministric as possible. -device falls into the 
latter category.


Alex