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Re: [Xen-devel] Memory Page Sharing on Xen 4.0.1

To: Sebastian Biedermann <biedermann@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Memory Page Sharing on Xen 4.0.1
From: veerasena reddy <veeruyours@xxxxxxxxx>
Date: Wed, 29 Jun 2011 21:26:31 +0530
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
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I think you have followed the older (which is complicated) procedure "How to compile Xen pv drivers for Linux HVM on a modern kernel" in the link.

Please try the latest write-up "Linux PV drivers for Xen HVM – building normally within an arbitrary kernel tree" in the same webpage. Here is the separate link to that:
Go the line "To install, simply apply this patch to your kernel build tree, and build as normal." and click on "this patch" highlighted.
This patch adds drivers/xenpvdrivers/ and include/xenpvdriers/ directories to your kernel sources.

Regarding configuration file:
Use the config file of ubuntu-10.04 default kernel "/boot/config-xx.yy.zz" as the base and do menuconfig, disable CONFIG_XEN and enable CONFIG_XEN_PVDRIVERS as module (CONFIG_XEN_PVDRIVERS=m)
# download kernel and the xen_pvdriver patch from the above link "pvdrivers.20100509-1955.patch"
# tar zxf
# cd linux-
# patch -p1 < path_to_patch_downloaded /* apply the patch */
   verify whether drivers/xenpvdrivers and include/xenpvdrivers created or not after the patch?
# cp /boot/config-<ubuntu_10_04_kernel_version> .config
# make menuconfig
   disable PV Guest support
   Processor type and features  ---> [] Paravirtualized guest support  --->
   This internally disables CONFIG_XEN
# enable CONFIG_XEN_PVDRIVERS option
    Device Drivers  --->
    <M> Xen pvdrivers
      [*]   Scrub pages before returning them to system
# go ahead with rest of the build/install procedure.


On Wed, Jun 29, 2011 at 8:11 PM, Sebastian Biedermann <biedermann@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

I will explain that a bit further...

dom0: Ubuntu 10.04-2 (amd64) kernel running Xen 4.0.1 (amd64)

    -> could easily compile and start dom0_working

domU: Ubuntu 10.04 (i386)
    -> downloading kernel sources of kernel
    -> patching with "pvdrivers-0.01/xenify.sh xen-patches-2.6.32-1.tar.bz2" (works perfect)
    -> copy the existing /boot/config- to this kernel sources (thats correct?)
    -> make menuconfig and just save & exit

If I now look at the .config of the kernel, there is no CONFIG_XEN_PVDRIVER option

    -> make localmodconfig
    -> make -j 9
    -> cd pvdrivers-0.01 and ./build.sh (works)

Then I install the new compiled kernel with "make install modules_install" and I restart.
Now I have booted the kernel in a HVM guest machine including additionally the pv modules, is that true?

Finally, the problem ist, that I cannot compile the domU_working,
because there are no pvxendrivers header files on the system.

I think I forgot one step or I have a general problem understanding the whole process.
Where can I get the xen header Files?

It tried it also with kernel 2.6.38 and Ubuntu 11.04, but I cloud not ./built the pvdrivers
because the compilation process termintated with
"Cannot compile, Error: linux- missing".

Thank you!

Am 29.06.2011 13:20, schrieb veerasena reddy:
I too used the same link (Linux PV drivers for Xen HVM – building normally within an arbitrary kernel tree)

Coulple of questions:
Could you please check whether your sources have include/xenpvdrivers after applying the patch.
Have you disabled CONFIG_XEN and enabled CONFIG_XEN_PVDRIVERS as module (CONFIG_XEN_PVDRIVERS=m)
Also, could you please share the error log.

Thanks & Regards,
On Wed, Jun 29, 2011 at 3:41 PM, Sebastian Biedermann <biedermann@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Awesome, thank you very much!

dom0 source compiles without problems!
domU source cannot find the xen headers:

#include <xenpvdrivers/evtchn.h>
#include <xenpvdrivers/xenbus.h>
#include <xenpvdrivers/interface/io/netif.h>
#include <xenpvdrivers/interface/memory.h>
#include <xenpvdrivers/balloon.h>
#include <xenpvdrivers/asm/maddr.h>

I compiled in the PV HVM modules using this tutorial:

And built them into the guest kernel, it runs fine, but I dont have the right headers.

Can you tell me which xenpvdrivers headers you are using and where they come from?
Because e.g. I cannot find the asm/maddr.h in the xen sources.. or anywhere else

Tank you !

Am 28.06.2011 15:24, schrieb veerasena reddy:

I tried the same links but had to make some changes to get it working.
Please find attached the sample working files for sharing a domU HVM page to dom0.
It has been tested xen-4.0.1 and HVM guest running ubuntu 10.10 with kernel version (from kernel.org) compiled with CONFIG_XEN disabled and PVHVM drivers compiled in as modules.

1. Set LINUX_ROOT appropriately in Makefiles of dom0 and domU.
2. Set remote domain in dom0 appropriately "info.remoteDomain = <domU_domain_id>"
3. Compile modules dom0 and domU respectively on dom0 and domU guest.
4. Load module on domU first.
    # insmod ./domu_share.ko
5. do "dmesg" on domU and note down the grant reference number
    [ 1293.316240]  gref = 770   <<<--- this is the grant reference number
6. now load the module on dom0 by passing grant reference number as module param
    # insmod ./dom0_share.ko gref=770
7. do dmesg on dom0
======== dmesg on dom0 =====
    xen: dom0: init_module with gref = 770
xen: dom0: shared_page = 269f4000, handle = 9, status = 0
Bytes in page aseem sethi
XEN: dom: end init_module

Thanks & Regards,

On Tue, Jun 28, 2011 at 5:50 PM, Sebastian Biedermann <biedermann@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Dear List,

I´m trying to figure out memory page sharing using HVM on Xen 4.0.1,
but I´m not really able to find some useful information or sources about this issue.

I just found two links porviding these sources:


Both are not working.. I think they are made for an older version of xen.

Additionally I thought about checking the code of:


..which is located in the Xen source, but that´s very complicated and I dont know what I need
for a simple page exchange using own programmed standalone tools between two running domains.

Can anyone help me by sending some useful links or can anyone give me a hint where to start?

Thank you a lot!

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Sebastian Biedermann
Security Engineering Group
Technische Universität Darmstadt

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Sebastian Biedermann
Security Engineering Group
Technische Universität Darmstadt

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