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Re: [Xen-devel] How ARM Xen process the harddisk requests from DomU

To: Josh Zhao <joshsystem@xxxxxxxxx>
From: Ian Campbell <ian.campbell@xxxxxxxxxx>
Date: Tue, 13 Aug 2013 21:40:33 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Tue, 13 Aug 2013 20:40:54 +0000
List-id: Xen developer discussion <xen-devel.lists.xen.org>

On Mon, 2013-08-12 at 14:23 +0800, Josh Zhao wrote:
> As the dom0 can use map_devices_from_device_tree() to map all devices
> into dom0 memory space , why we need to use the sysmmu ?

All ARM domains run with hardware nested page tables ("second stage
paging" in ARM speak, equivalent to HAP for x86 HVM guests). So an IOMMU
is needed to translate guest physical addresses into host physical
addresses for the device e.g. for doing DMA.

Ian.

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References:
- [Xen-devel] How ARM Xen process the harddisk requests from DomU
  - From: Josh Zhao
- Re: [Xen-devel] How ARM Xen process the harddisk requests from DomU
  - From: Josh Zhao

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