How ARM Xen process the harddisk requests from DomU

How ARM Xen process the harddisk requests from DomU

[Josh Zhao]

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Hi,
I am wondering how arm xen process the harddisk requests from DomU, is
there a daemon in dom0 to do this work?

Thanks,

Josh

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Re: How ARM Xen process the harddisk requests from DomU

[Josh Zhao]

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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 ?


2013/8/12 Josh Zhao <joshsystem@gmail.com>

> Hi,
> I am wondering how arm xen process the harddisk requests from DomU, is
> there a daemon in dom0 to do this work?
>
> Thanks,
>
> Josh
>

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Re: How ARM Xen process the harddisk requests from DomU

[Ian Campbell]

On Mon, 2013-08-12 at 12:06 +0800, Josh Zhao wrote:

> I am wondering how arm xen process the harddisk requests from DomU, is
> there a daemon in dom0 to do this work?

Xen on ARM supports only PV devices, so the PV disk backend will deal
with it. I'm not sure anyone has tried qdisk on ARM, although it should
work fine, but I expect most people are currently using the in-kernel
blkback driver in their driver domain.

Ian.

Re: How ARM Xen process the harddisk requests from DomU

[Ian Campbell]

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.