linux-kernel - Re: [PATCH 2/5] iommu/amd: Implement DOMAIN_ATTR

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Message-ID: <20120130143010.GS19255@amd.com>
Date:	Mon, 30 Jan 2012 15:30:10 +0100
From:	Joerg Roedel <joerg.roedel@....com>
To:	Sethi Varun-B16395 <B16395@...escale.com>
CC:	Wood Scott-B07421 <B07421@...escale.com>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Tony Lindgren <tony@...mide.com>,
	Hiroshi DOYU <Hiroshi.DOYU@...ia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	David Brown <davidb@...eaurora.org>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH 2/5] iommu/amd: Implement DOMAIN_ATTR_GEOMETRY attribute

On Mon, Jan 30, 2012 at 06:27:30AM +0000, Sethi Varun-B16395 wrote:

> Can you please explain how would IOMMU remapping be used, based on the
> force_aperture flag.

If force_aperture is flase the dma-api code needs to check if remapping
is required at all. It performs the following checks:

	* Does the physical address of the buffer not overlap with the
	  aperture?
	* Fits the buffer into the device's dma address mask?

If both questions are answered with yes no remapping is required and
dma-api just returns the physical address. Otherwise it calls into the
dma-api to create a mapping.


	Joerg

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