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RE: [Xen-users] Supported Dom U platform

To: "Anh Nguyen" <nguyenminhanh@xxxxxxxxx>
Subject: RE: [Xen-users] Supported Dom U platform
From: Jeff Sturm <jeff.sturm@xxxxxxxxxx>
Date: Tue, 4 May 2010 15:33:40 -0400
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Thread-topic: [Xen-users] Supported Dom U platform

To your 2nd question, there are several broad classes of devices widely used in PV domains:  Block, net and console (which are the only ones I care about in my deployments), USB (new to 4.0), SCSI and PCI.  All these follow the front/back device model.  Graphical consoles in a PV domain may be used over any applicable network protocol (e.g. X11, VNC).

 

I've never heard of a floppy disk or pc speaker for a PV domain.  I'd be curious as to who would need such a thing.

 

(I don't know the answer to your other question, and to be honest I haven't looked at recent source.  We've been getting by on the kernels in CentOS 5.x, supplemented with the gitco RPM builds, for expediency's sake.)

 

From: Anh Nguyen [mailto:nguyenminhanh@xxxxxxxxx]
Sent: Tuesday, May 04, 2010 2:41 PM
To: Jeff Sturm
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Supported Dom U platform

 

Thanks Jeff,

 

That certainly answered my previous questions. But leads to other ones :)

 

1. Why is the code for binary translation and emulation of MIPs, Sparc... and so on still exists in xen.3.4.2 default source ball (in tools\ioemu-qemu-xen). Is it because no one find the need / or want to go through all the hassle to remove them from qemu-xen code just to save a few KB? 

2. If PV domains don't use QEMU. How are core devices normally attached to the motherboard, such as keyboard controller, floppy disk controller, pc speaker, emulated for PV domains? Do they also follow the frontend / backend drivers model? If so where can I find the code for their frontend / backend drivers?

 

Thanks a lot,

On Tue, May 4, 2010 at 10:20 AM, Jeff Sturm <jeff.sturm@xxxxxxxxxx> wrote:

Xen does virtualization, not emulation.   It supports several CPU architectures, but your domU sees the same CPU as your dom0.

 

That said, on x86-64 platforms you can mix/match 32-bit and 64-bit domains provided the hypervisor is a 64-bit build.   This works because the underlying hardware supports it, not because any emulation is taking place.

 

As I understand it Xen uses QEMU solely for device emulation.  It's required for HVM domains.  Pavarvirtualized domains don't need QEMU at all.

 

From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Anh Nguyen
Sent: Saturday, May 01, 2010 7:24 PM
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Supported Dom U platform

 

Hi everyone,

 

I have two questions:

 

1. Does anyone knows if Xen supports running Dom U (guest) platforms other than x86 and amd64? For examples: MIPs, arm...

I see MIPs and ARM related code inside tools\ioemu-qemu-xen but I am not sure if that is enough.

 

2. My understanding is Xen uses QEMU for HVM device emulation, and QEMU uses binary translation. Does that mean Xen HVM guests will have to go through the binary translation layer? Is this the case if the guest platform and the host platform are the same?

 

Best,

 

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