Re: [Xen-devel] Xen on ARM basic questions

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-11-18 at 13:57 -0500, Vaibhav Bedia wrote:
> Hi,
> 
> I have a couple of basic questions regarding the Xen on ARM (with
> virtualization extensions). It probably falls under WIP but i thought
> i'll ask anyway.
> 
> 1. Using the current unstable Xen on ARM code is it possible to
> virtualize network, usb, sata and things like that? I looked at the
> wiki pages for Arndale, VExpress but could not figure out whether this
> is supported right now. If not, are there any patches that i can
> try out?

Xen on ARM does not expose real USB/SATA/network etc to the guests/domU.

All of the physical devices are exposed only to dom0 which in turn
provides "paravirtualised" virtual devices for disk, network and console
which are exposed to the guest.

There is currently no PV usb for Xen on ARM, although there is some work
ongoing on x86 which may be reuseable.

Eventually we will also support physical device passthrough which would
allow you to dedicate each device (USB controller, SATA controller, NIC
etc) to a single guest.

>  After going through the recent talk from Stefano [1] i got
> the impression getting network and SATA requires SWIOTLB support. Is
> that correct?

The SWIOTLB or an IOMMU/SMMU is necessary for dom0 to drive the physical
devices and provide the virtual interfaces to the guests.

Device passthrough will only be supported with an IOMMU/SMMU.

> 2. For domU to see the network and SATA interfaces is the DTB supposed
> to be updated? Is there some guideline on how to do this? Do i just
> add in the nodes similar to dom0?

Hopefully the above has made this question moot.

> Right now i have an OMAP5 dom0 with network+usb support and i am
> trying to figure out how to get these things in domU and hence the
> questions.

You need blkback and netback in dom0 and blkfront and netfront in domU
(all in mainline Linux). Then you need to add vif and disk options to
your guest configuration.

Ian.


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