Re: [Qemu-devel] Re: [PATCH v2 9/9] Add -kvm option

[Anthony Liguori <aliguori@us.ibm.com>]

Gerd Hoffmann wrote:
>> qemu should not have the concept of a default nic.
>
> Well, right now it has (likewise for serial, vga, ...).  And it causes 
> problems with the qdev way of managing devices, so we have to find a 
> way to deal with it.

There are a few separate issues that should be treated differently.  For 
vga, it should just be a default device in the machine description.  A 
special id should be used for the default vga card and -vga std should 
have the effect of modifying the a vga device of that id to be std.  
IOW, it should be -device-remove id=default_vga -device 
stdvga,id=default_vga.

For serial, we default to having one port.  Again, it should have a well 
known id and -serial none should be -device-remove id=default_serial.  
For nics, it's a bit complicated by the fact that -net nic doesn't 
require a model and by default, each machine may have a default model.  
We will likely have to preserve this as a config option which is 
unfortunate.

That said, without -net none, we get a single network device.  Again, it 
should have a well known id and -net none should remove that device.
> Right now the default devices are tied to a command line switch, i.e. 
> in case there isn't a -serial switch specified qemu will add a default 
> serial device, even in case one was added via -device isa-serial.

I don't think -device has to have the same property of -serial.  That 
is, -device isa-serial doesn't need to replace the default serial device 
which is connected to a vc.  Rather, we should allow a user to modify 
the char device associated with that default serial device via -set.
 
We shouldn't think of it like we add a default -serial device if no 
-serial switch was used.  Instead, there has always been a default 
isa-serial device.  You can modify it via -set or you can remove it.  
-serial none removes it.  For the first occurrence of -serial, it 
behaves like -set.  Future occurrences of -set behave like -device 
isa-serial.

-- 
Regards,

Anthony Liguori