Re: [Xen-devel] Several questions from a freshman to Xen

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Oct 13, 2011 at 11:51:01PM +0800, Zhengwang Ruan (Royo) wrote:
> Hi Guys,
>

Hello,

> I am new man with some confusions to this amazing technology, hope you  
> guys give answers to help me better understand Xen. :)
>

Maybe this wiki page gives some general info about Xen:
http://wiki.xen.org/xenwiki/XenOverview


And these PDFs:
http://xen.org/files/Marketing/WhatisXen.pdf
http://xen.org/files/Marketing/WhyXen.pdf


> 1, You guys have been working on developing many releases, do you guys  
> have agreements on developing every source code based on a fixed linux  
> kernel version before starting a new release? If so, how could I know  
> the corresponding kernel version to a given xen release? I tried to find  
> answer for myself on the following wiki page, but it is not latest 
> enough.
>

Are you talking about dom0 kernel? or domU kernel?

Xen hypervisor (xen.gz) is the compatibility layer,
so dom0 and domUs (VMs) can all have different Linux kernel versions.

> http://wiki.xen.org/xenwiki/DistributionSupport
>
> 2, I found some interesting source files in xen-4.1.1 release, I listed  
> them below:
>
> $ ll
> drwx------ 4 royo royo 16384 2011-10-12 00:20 arch/
> drwx------ 5 royo royo 16384 2011-06-15 00:03 common/
> -rw-r--r-- 1 royo royo 19185 2011-06-15 00:03 COPYING
> drwx------ 2 royo royo 16384 2011-06-15 00:03 crypto/
> drwx------ 8 royo royo 16384 2011-06-15 00:03 drivers/
> drwx------ 9 royo royo 16384 2011-06-15 00:03 include/
> -rw-r--r-- 1 royo royo  5529 2011-06-15 00:03 Makefile
> -rw-r--r-- 1 royo royo  3498 2011-06-15 00:03 Rules.mk
> drwx------ 3 royo royo 16384 2011-06-15 00:03 tools/
> drwx------ 4 royo royo 16384 2011-06-15 00:03 xsm/
>
> Are these files going to replace or be added to linux kernel source  
> while making dm0? I am amazed that this release can be installed to many  
> linux distributions with different kernel, how could you guys achieve 
> this?
>

Xen hypervisor (xen.gz) is a totally separate binary, it's not "mixed" to/with 
Linux kernel.

- For Xen dom0 you need to use a Linux kernel that has Xen dom0 support enabled.
- For Xen PV domUs (VMs) you need to use a Linux kernel that has Xen PV domU 
support enabled.
- For Xen HVM VMs you don't need a special kernel, but having Xen PVHVM drivers 
in the kernel will boost disk/net performance.

Xen related features in different Linux kernel versions:
http://wiki.xen.org/xenwiki/XenParavirtOps


-- Pasi


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