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. > -- > error compiling committee.c: too many arguments to function
