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

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Message-ID: <4C2D9575.9030002@codeaurora.org>
Date:	Fri, 02 Jul 2010 00:29:57 -0700
From:	Zach Pfeffer <zpfeffer@...eaurora.org>
To:	Hari Kanigeri <hari.kanigeri@...il.com>
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@...per.es
Subject: Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager

Hari Kanigeri wrote:
>> The VCMM takes the long view. Its designed for a future in which the
>> number of IOMMUs will go up and the ways in which these IOMMUs are
>> composed will vary from system to system, and may vary at
>> runtime. Already, there are ~20 different IOMMU map implementations in
>> the kernel. Had the Linux kernel had the VCMM, many of those
>> implementations could have leveraged the mapping and topology management
>> of a VCMM, while focusing on a few key hardware specific functions (map
>> this physical address, program the page table base register).
>>
> 
> -- Sounds good.
> Did you think of a way to handle the cases where one of the Device
> that is using the mapped address crashed ?
> How is the physical address unbacked in this case ?

Actually the API takes care of that by design. Since the physical
space is managed apart from the mapper the mapper can crash and not
affect the physical memory allocation.

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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