Re: [Qemu-devel] [PATCH v2] q35: Improve sample configuration files

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,

> > If you add a video card manually (via -device or config file entry) qemu
> > will not add the default video card.
> > 
> > Likewise, if you add a NIC manually, qemu will not add the default
> > ethernet device (and IIRC creating the default netdev will be skipped
> > too).
> 
> This has the potential to give you some unexpected results

Indeed.

> but I'd say it's still entirely reasonable.

Well, makes it easy for users to get started, just "qemu -cdrom $live"
gives you a usable virtual machine without having to worry too much
about what devices you want plug in.

But that kind of magic -- while convenient at times -- can also easily
get into the way.  Guess why the -nodefaults switch exists ...

> So what do you think, should q35-emulated.cfg recommend the
> use of -nodefaults the same way q35-virtio-*.cfg do and add
> the video card (cirrus-vga?) and Ethernet adapter explicitly?

I think that would be good, for consistency across all q35*.cfg files.

But please don't use cirrus[1], it isn't the default any more for good
reasons.  I'd suggest to go with our new default, which is stdvga
(-device VGA), as we don't have intel graphics emulation.

> The advantage in doing so would be that we would provide
> maybe slightly more documentation, and we would be able to
> plug the Ethernet adapter at 19.0 instead of 02.0, which as
> I understand it matches real hardware better.

Yes.

cheers,
  Gerd

[1]
https://www.kraxel.org/blog/2014/10/qemu-using-cirrus-considered-harmful/