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Re: [virt-tools-list] Emulating raspberry pi (arm1136-r2) in virt-manager?




On 15/02/13 09:11, Martin Kletzander wrote:
On 02/14/2013 09:01 PM, Cole Robinson wrote:
On 02/14/2013 09:26 AM, Simon Lambourn wrote:
Hi,  I'm sure I am not the only person to want to do this:

I can emulate raspberry pi using their disk image using raw qemu-system-arm,
but I cannot find the right CPU machine type in virt-manager.  Has anyone
found how to do this, or can someone offer advice please?

The command I have used to start the raspberry pi emulation (on Ubuntu 12.10) is

qemu-system-arm -kernel kernel-qemu -cpu arm1136-r2 -m 192 -M versatilepb
-no-reboot -serial stdio -append "root=/dev/sda2 panic=1" -hda
debian6-17-02-2012.img

I downloaded the debian6...img file from the raspberry pi site. This all works
fine but I would like to set up a VM definition in virt-manager if possible.
In the dialog to create a new virtual machine I selected "import existing OS
image" and then on screen 4 "customise configuration before install", virt
type=qemu and architecture = arm.   Then I press Finish to customise the
configuration.    In Overview I select Machine type = versatilepb (and in Disk
type I select disk bus=IDE and storage format=Raw, but I'm not sure this is
important).

However I can't find where or how to enter the cpu type - on the processor
page I have tried setting Model (under configuration) to arm1136, 1136,
arm1136-r2 and none of these are accepted by qemu. If I leave the Model type
blank I get a different error (HDA full duplex not supported by this binary).

libvirt + qemu-system-arm don't play together too well at the moment. I don't
think you will be able to do what you want to do without some qemu wrapper
script. There's some hints here:

https://fedoraproject.org/wiki/Architectures/ARM/HowToQemu#Using_QEMU_with_libvirt

The plan is to make this all 'just work' in libvirt + virt-manager, but no
time table yet.

- Cole

Just confirming what Cole said; we tried to achieve something similar
few days ago.  The thing is, though, that libvirt supports mainly
emulating PCs in QEMU.  There are many things that aren't very easily
fixable.  Completely different devices must be specified in some
scenarios and some QEMU versions even expect different parameters when
running arm emulation (for the same options as the PC emulation).
Controllers are different, there is no PCI bus, but libvirt
automatically adds that and many many more things.

As suggested, the best way to make it work is try to make it "just work"
and don't expect too much.  There are many wrappers on the interwebz you
can use, two of them are in the link above.

Either you know that already or you'll learn that when reading the first
howto, but to briefly explain how that works; there is '<emulator>'
element in libvirt's domain XML and that says what binary (script)
should be used to run that particular machines.  You can create your
script, put it there and just make sure in the script that you mangle
the command-line enough so QEMU will start when you exec() it at the
end.  The less you change it, the more you may get out of it (networking
and such).

My 0.02$,
Martin

Martin & Cole - thank you for the advice and pointers. I have made some progress but I'm now stuck again.

From what you say above, it seems that virt-manager is unlikely to allow definition of a raspberry pi in the near future, but it may be possible using libvirt/virsh.

Following the link above led me to an xml definition for an arm machine, which I copied and changed to match the qemu-system-arm command string (above) that worked for me. When I try and start this VM I get an error: "error: unsupported configuration: CPU specification not supported by hypervisor". The CPU element I'm using is

  <cpu match='exact'> <model>arm1136-r2</model>   </cpu>

The guidance says that valid CPU models are in the cpu_map.xml file, but this only seems to cover the X86 architecture. So is there another way of specifying the model in the XML file? I'm looking to replicate the qemu-system-arm parameter -cpu arm1136-r2.

Any ideas would be welcome.
Simon



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