Re: [Qemu-devel] [PATCH v5 2/2] mach-virt: Provide sample configuration files

[Andrew Jones]

On Thu, Feb 09, 2017 at 11:51:13AM +0100, Andrea Bolognani wrote:
> On Thu, 2017-02-09 at 09:57 +0000, Peter Maydell wrote:
> > > I see Peter and you are discussing what to document here. IMO,
> > > we should simply state -nodefaults provides us a base mach-virt
> > > board with no peripherals.
> > 
> > The thing about saying that is that it's not actually
> > correct -- you get the UART, etc etc peripherals whether
> > you say -nodefaults or not. I agree that listing them
> > in multiple places isn't a good idea though. Maybe
> > there's some wording that will work here.
> 
> Agreed, we just have to find the right wording. Would
> something like
> 
>   Using -nodefaults is required to have full control over
>   the virtual hardware: when it's specified, QEMU will
>   only automatically add a small selection of core PCI
>   devices, and leave the user in charge of adding more as
>   they see fit. More specifically, the PCI devices that
>   will always be present are:
> 
>     00:00.0 Host bridge
> 
>   This configuration file adds a number of other...
> 
> work for you? Please keep in mind that I want to be able
> to use the very same paragraph both for q35 and mach-virt.

I'm not sure having the exact same paragraph is a reasonable
goal. Does q35 have platform devices like mach-virt? The
devices we get on a 'qemu -nodefaults -machine virt' instance
are MMIO driven devices on the board, rather than devices
hung off the pcie host bridge.

Perhaps we can list the uart as an example; I don't suppose
it'll ever be removed. If we use wording such as "such as",
then it allows expansion to the board without a commitment to
update the list.

BTW, when I stated "-nodefaults provides us a base mach-virt
board with no peripherals.", I meant no _additional_
peripherals plugged into the board's virtio-mmio transports,
nor hung off the host bridge. Is there a word for those?
Maybe just non-builtin peripherals?

Thanks,
drew

> 
> -- 
> Andrea Bolognani / Red Hat / Virtualization
>