Re: [Qemu-devel] [PATCH] pci: add standard bridge device

[Avi Kivity]

On 08/28/2011 02:41 PM, Michael S. Tsirkin wrote:
> >
> >  If it really matters, you can add a prefetchability attribute to
> >  MemoryRegions.  Does it though?
>
> Well, its another one of these things that
> guests *probably* won't in practice use.
> But I don't see a way to be sure.
>
> If the guest puts a prefetcheable memory BAR behind
> a non-prefetcheable range in the bridge, it won't
> be able to access that BAR, and it should.

Not sure I understand - on real hardware, does it see the BAR or not?

> Prefetcheable BARs on devices are less common than
> non-prefetcheable, but they do exist:
> I have a system with 2 devices: a VGA controller from Matrox
> and an ethernet card from Mellanox have
> prefetcheable BARs.
>
> I'm not sure how prefetcheability attribute will help.
> Could you explain pls?

Have an attribute for a region "does not allow prefetchable memory" in 
subregions
Have an attribute for a region "prefetchable memory"

When rendering the memory map, ignore any "prefetchable memory" regions 
that are subregions of a "does not allow prefetchable memory" region.

(if I understood correctly - not sure)

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