Re: [Qemu-devel] PCI access virtualization

[Paul Brook]

> > IIUC PCI cards don't really have "DMA engines" as such. The PCI bridge
> > just maps PCI address space onto physical memory. A Busmaster PCI device
> > can then make arbitrary acceses whenever it wants. I expect the default
> > mapping is a 1:1 mapping of the first 4G of physical ram.
>
> I was under the impression that the on-card bus-mastering engines were
> often one of a few standard designs -  this was suggested to me by someone
> more knowledgeable than myself but must admit I don't have any hard
> evidence that it's the case ;-)

What about 64-bit systems that use an IOMMU? Don't they already have a 64-bit 
physical -> 32-bit IO address space mapping? I don't know if this mapping is 
per-bus or system global.

Paul