Re: [Qemu-devel] [PATCH 01/10] Add stub functions for PCI device models to do PCI DMA

[Anthony Liguori]

On 09/01/2011 11:11 AM, Avi Kivity wrote:
> On 09/01/2011 07:05 PM, Anthony Liguori wrote:
> > > I think the patchset is fine. It routes all access through pci_dma_rw(),
> > > which accepts a PCIDevice. We can later define pci_dma_rw() in terms of
> > > the memory API and get the benefit of the memory hierarchy.
> >
> >
> > The challenge is what you do about something like ne2k where the core
> > chipset can either be a PCI device or an ISA device. You would have to
> > implement a wrapper around pci_dma_rw() in order to turn it into
> > cpu_physical_memory_rw when doing ISA.
>
> True. But I still think it's the right thing.
>
> We can't really pass a MemoryRegion as the source address, since there
> is no per-device MemoryRegion.

Couldn't the PCI bus expose 255 MemoryRegions though?  It could still 
use the pci_address_space I think since that should include RAM too, right?

In fact, initially, you could have a 
pci_bus_get_device_memory_region(bus, dev) that just returns 
pci_address_space().

You just need the memory_st[bwl] functions I think.

Regards,

Anthony Liguori

 We can use pci_address_space() for basic
> offsetting, and for bypassing bridge windows, but iommu source detection
> has to use the PCIDevice directly.