From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnd@arndb.de (Arnd Bergmann)
Date: Tue, 02 Sep 2014 14:43:18 +0200
Subject: [RFC PATCH 0/7] Introduce automatic DMA configuration for IOMMU
 masters
In-Reply-To: <5405B6F2.1060105@samsung.com>
References: <1409327670-3495-1-git-send-email-will.deacon@arm.com>
 <20140902105730.GH25379@arm.com> <5405B6F2.1060105@samsung.com>
Message-ID: <3133975.8bg0CLVMMz@wuerfel>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tuesday 02 September 2014 14:24:18 Marek Szyprowski wrote:
> >>> For isolation purposes, it can only help to have more domains, but
> >>> I would guess that there is some space overhead in maintaining lots
> >>> of page tables.
> >> I'm okay with both approaches (separate domain for each device vs. single
> >> common domain for all devices). Maybe this can be some kind of Kconfig
> >> option added to DMA debugging? Separation might be really helpful when
> >> debugging strange device behavior.
> > One potential problem with a single domain is when you have multiple
> > instances of a given IOMMU, each with different hardware restrictions.
> > Then you can end up with multiple sets of page tables for the domain
> > which, although not impossible to work with, is a bit of a mess.
> 
> Maybe the default dma-mapping domain should be one per a given IOMMU 
> instance?
> This will simplify a lot of things in such case.

Yes, that sounds like a good idea.

	Arnd