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Re: [Qemu-devel] [PATCH 2/6] PCI DMA API

From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH 2/6] PCI DMA API
Date: Sun, 30 Mar 2008 09:44:57 -0500
User-agent: Thunderbird (X11/20080227)

Blue Swirl wrote:
On 3/30/08, Anthony Liguori <address@hidden> wrote:
This patch introduces a PCI DMA API and some generic code to support other DMA
 APIs.  Two types are introduced: PhysIOVector and IOVector.  A DMA API
 maps a PhysIOVector, which is composed of target_phys_addr_t, into an IOVector,
 which is composed of void *.

This looks like it wouldn't scale to handle the Sparc systems. There
we want to make more translation steps from DVMA addresses to physical
in DMA controller and IOMMU and only in the final stage to void *. To
handle this, probably there should be an opaque parameter and some way
to register the translation function. Otherwise the API looks OK.

I think having the PCI DMA API translate PhysIOVector => PhysIOVector would help. Then it becomes pretty easy to just call the DMA controller for additional translation from the IOMMU.

Does that sound right? I don't quite understand what role the opaque parameter would serve.


Anthony Liguori

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