linux-kernel - Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager

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Date:	Sat, 10 Jul 2010 17:11:11 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Zach Pfeffer <zpfeffer@...eaurora.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Daniel Walker <dwalker@...eaurora.org>,
	Randy Dunlap <randy.dunlap@...cle.com>, mel@....ul.ie,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager

On Thu, Jul 01, 2010 at 11:17:34PM -0700, Zach Pfeffer wrote:
> Andi Kleen wrote:

> > Hmm? dma_map_* does not change any CPU mappings. It only sets up
> > DMA mapping(s).
> 
> Sure, but I was saying that iommu_map() doesn't just set up the IOMMU
> mappings, its sets up both the iommu and kernel buffer mappings.

What do you mean by kernel buffer mappings?


> > That assumes that all the IOMMUs on the system support the same page table
> > format, right?
> 
> Actually no. Since the VCMM abstracts a page-table as a Virtual
> Contiguous Region (VCM) a VCM can be associated with any device,
> regardless of their individual page table format.

The IOMMU-API abstracts a page-table as a domain which can also be
associated with any device (behind an iommu).

	Joerg

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