Re: [Qemu-devel] [RFC] Proposal: PCI/PCIe: inbound BAR0 emulation for PCI controller (Root Complex)

[Benjamin Herrenschmidt]

On Fri, 2012-06-08 at 14:08 -0500, Scott Wood wrote:
> > Yes, that's basically it. The patches allow you to add a set of
> routines
> > that will be used for translating DMA accesses to system memory
> along
> > with map/unmap operations etc...
> 
> How easy is it to have multi-level translation -- PCI controller
> translates PCI transactions to host DMA addresses, and the system
> IOMMU
> translates that into a physical address? 

Multi level would mean a translation layer at every bridge level, which
sucks big time in term of performances. At the moment the patches
provide a way to hook a translate function at the bus level.

Cheers,
Ben.