On Fri, Jun 18, 2010 at 10:38:20PM +0900, Isaku Yamahata wrote: > On Fri, Jun 18, 2010 at 03:44:04PM +0300, Michael S. Tsirkin wrote: > > > > If I understand correctly what this does, it goes over > > > > other functions of the same device, and sets the MULTI_FUNCTION bit > > > > for them if there's more than one function. > > > > Instead, why don't we just set PCI_HEADER_TYPE_MULTI_FUNCTION > > > > in relevant devices? > > > > > > pci address, devfn ,is exported to users as addr property, > > > so users can populate pci function(PCIDevice in qemu) > > > at arbitrary devfn. > > > It means each function(PCIDevice) don't know whether pci device > > > (PCIDevice[8]) is multi function or not. > > > So I chose to handle it in pci generic layer. > > > > > > It can be argued that it's user operation fault and that > > > the missing part is validation checks to catch such user errors. > > > > Exactly. Another part that is missing is a way to hotplug > > a multifunction device. > > Yes, multi function hot plug is also on my wish list. > > > > OTOH I think that hotplug of separate functions has no chance to work, > > so users are better off getting an error. > > > > > But I prefer more flexible and more user friendly way. > > > > I think that most users would only add many functions > > to a device as a result of an error. > > > > If we really want the ability to put unrelated devices > > as functions in a single one, let's just add > > a 'multifunction' qdev property, and validate that > > it is set appropriately. > > I think "unrelated" is policy. There is no obvious way to determine > which functions can be in a same device. > For example, popular chipset contains isa bridge, ide controller, > usb controller, sound and modem in a single device as functions. > It's up to hardware designer policy which functions are grouped into > a device. > > So qemu should be able to populate any function in a device, > and leave such policy check to higher level tool like libvirt/virt-manager.
Fine. But let's keep it simple: ask user what multifunction bit is, and not tweak header for device A when device B is added. > -- > yamahata
