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

["Zhengwang Ruan (Royo)" <zhengwang.ruan@xxxxxxxxx>]

On 2011年10月14日 03:07, Pasi Kärkkäinen wrote:

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.

Hi Pasi,


I refer to dom0 here. I got many details on wiki http://wiki.xen.org/xenwiki/XenParavirtOps , it helps me understand some.

From this page, I know you guys developed xen-3.x based on linux-2.6.18, and and xen-4.x on 2.6.32, am I right? So these two versions of kernel should be supported mostly, right?

For domU, each kernel from kernel.org should be working as a guest?

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.

And, xen-4.1.1 is compiled to generate xen.gz which is started by dom0 and running on/inside dom0 as Hypervisor?

- 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 

PVHVM drivers are implemented using xenbus? The drivers in xenbus/ directory are you called PVHVM drivers?

Thanks,
Royo

performance.

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


-- Pasi

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