Re: [Qemu-devel] Supporting emulation of IOMMUs

[David Gibson]

On Thu, Apr 28, 2011 at 02:57:14PM -0700, Richard Henderson wrote:
> On 04/21/2011 02:39 AM, Alexander Graf wrote:
> > How exactly is this going to be used? Also, in the end I think that
> > most devices should just go through a PCI specific interface that
> > then calls the DMA helpers:
> > 
> > pci_memory_rw(PCIDevice *d, ...)
> > 
> > even if it's only as simple as calling
> > 
> > dma_memory_rw(d->iommu, ...)
> 
> I've had a read through the patches posted in January.  It all does
> seem relatively sane.  At least, I can readily see how I would apply
> these interfaces to my Alpha port without trouble.
> 
> I'll agree with Alex though that the raw dma_memory_rw functions 
> should not be exposed to the drivers for any given bus.  They should
> always go through {pci,isa}_memory_rw.  And these should almost 
> certainly be inline functions that just pass on &device->bus.mmu.

I don't really see the point of having per-bus helpers.  This is going
to be widespread enough that we can have an iommu pointer in the core
qdev, then everything can use the same helpers.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson