Re: [Qemu-devel] Supporting emulation of IOMMUs

[David Gibson]

On Thu, Apr 21, 2011 at 11:39:22AM +0200, Alexander Graf wrote:
> On 21.04.2011, at 09:03, David Gibson wrote:
[snip]
> > @@ -934,6 +939,8 @@ echo "  --enable-docs            enable documentation 
> > build"
> > echo "  --disable-docs           disable documentation build"
> > echo "  --disable-vhost-net      disable vhost-net acceleration support"
> > echo "  --enable-vhost-net       enable vhost-net acceleration support"
> > +echo "  --disable-iommu          disable IOMMU emulation support"
> > +echo "  --enable-vhost-net       enable IOMMU emulation support"
> 
> eeh?

Oops, copy and paste error.  Fix in my tree now.

[snip]
> > +#else
> > +struct DMAMmu {
> > +    DeviceState *iommu;
> > +    DMATranslateFunc *translate;
> > +    QLIST_HEAD(memory_maps, DMAMemoryMap) memory_maps;
> > +};
> > +
> > +struct DMADevice {
> 
> How exactly is this going to be used? 

Well, the guts of the dma layer is not my work, so I can't really
answer that.

> 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, ...)

So, I was actually thinking it would make most sense to have an iommu
pointer in *every* qdev, PCI or otherwise, so that we just use
        dma_memory_rw(qdev, ...)
everywhere.  Obviously a NULL iommu pointer would fall back to no
translation.

-- 
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