On Tue, Nov 03, 2009 at 02:39:06PM +0200, Michael S. Tsirkin wrote: > On Tue, Nov 03, 2009 at 02:22:07PM +0200, Avi Kivity wrote: > > On 11/03/2009 01:47 PM, Michael S. Tsirkin wrote: > >> > >> If qemu is compiled with target phys address size 32 bit, emulated > >> devices can not support a 64 bit BAR. Therefore, according to PCI spec, > >> such devices should declare all BARs as 32 bit. > >> > >> > > > > What happens if you take a PCI card that supports 64-bit BARs and stick > > it into a machine that has a 32-bit physical address space? > > The firmware/OS will configure the BARs to below 4G. > > > >> I think you are right that guests on such systems really do not have a > >> way to address PCI devices if BAR is set beyond 4G. But pci emulation is > >> better off not relying on this, IMO. Makes sense? > >> > > > > No. Device emulation shouldn't change with the machine type. > > I agree. Issue is, we recompile the *devices* as well. > It's the device emulation that is broken when compiled > with target phys addr set to 32 bit, because all devices > take pcibus_t and cast it to target_phys_addr_t > and then do stuff with it. > > So such emulation should not claim to support 64 bit. > > Long term, we should fix all devices and *then* they can claim 64 bit > support always. As a nice side effect, we'll be able to avoid > rebuilding devices.
BTW, the right way to do this is probably to move mapping device memory out of devices proper and into pci. > > -- > > error compiling committee.c: too many arguments to function