[SeaBIOS] [Qemu-devel] [RFC PATCH 01/13] Generic DMA memory access interface

David Gibson dwg at au1.ibm.com
Thu Jun 2 12:22:05 CEST 2011

On Wed, Jun 01, 2011 at 08:16:44AM -0700, Richard Henderson wrote:
> On 06/01/2011 07:29 AM, Avi Kivity wrote:
> > On 06/01/2011 05:01 PM, Richard Henderson wrote:
> >> >  +        err = dev->mmu->translate(dev, addr,&paddr,&plen, is_write);
> >>
> >> I see you didn't take my suggestion for using an opaque callback pointer.
> >> Really and truly, I won't be able to use this as-is for Alpha.
> >>
> > 
> > Rather than opaques, please pass the DMA engine itself and use container_of().
> The dma engine object is currently sitting in the PCIBus structure.
> Which is private, and can't be extended by a host bridge implementation.
> The entire code could be re-arranged, true, but please suggest something
> reasonable.
> > We should be removing opaques, not adding them.
> See my followup elsewhere.  Opaques *can* be cleaner than upcasting,
> particularly if there are too many hoops through which to jump.

So, in the meantime, I've also done a version of Eduard's earlier
patches, with added support for the PAPR hypervisor managed IOMMU.

I have also significantly reworked how the structure lookup works,
partly because in my case I'l looking at IOMMU translation for non-PCI
devices, but I think it may also address your concerns.  I'm still
using upcasts, but there are less steps from the device to the IOMMU

I've been sick and haven't had a chance to merge my stuff with
Eduard's changes.  I'll post them anyway, as another discussion

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_!

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