Re: [Qemu-devel] [PULL 14/28] exec: make address spaces 64-bit wide

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jan 14, 2014 at 08:50:54AM -0500, Mike Day wrote:
> 
> "Michael S. Tsirkin" <mst@redhat.com> writes:
> 
> > On Fri, Jan 10, 2014 at 08:31:36AM -0700, Alex Williamson wrote:
> 
> > Short term, just assume 48 bits on x86.
> >
> > We need to figure out what's the limitation on ppc and arm -
> > maybe there's none and it can address full 64 bit range.
> >
> > Cc some people who might know about these platforms.
> 
> The document you need is here: 
> 
> http://goo.gl/fJYxdN
> 
> "PCI Bus Binding To: IEEE Std 1275-1994"
> 
> The short answer is that Power (OpenFirmware-to-PCI) supports both MMIO
> and Memory mappings for BARs.
> 
> Also, both 32-bit and 64-bit BARs are required to be supported. It is
> legal to construct a 64-bit BAR by masking all the high bits to
> zero. Presumably it would be OK to mask the 16 high bits to zero as
> well, constructing a 48-bit address.
> 
> Mike
> 
> -- 
> Mike Day | "Endurance is a Virtue"

The question was whether addresses such as 
0xfffffffffec00000 can be a valid BAR value on these
platforms, whether it's accessible to the CPU and
to other PCI devices.



-- 
MST