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 >
