XenParavirtOps
What is paravirt_ops?
paravirt_ops (pv-ops for short) is a piece of Linux kernel infrastructure to allow it to run paravirtualized on a hypervisor. It currently supports VMWare's VMI, Rusty's lguest, and most interestingly, Xen.
The infrastructure allows you to compile a single kernel binary which will either boot native on bare hardware (or in hvm mode under Xen), or boot fully paravirtualized in any of the environments you've enabled in the kernel configuration, and lately also as Xen dom0.
It uses various techniques, such as binary patching, to make sure that the performance impact when running on bare hardware is effectively unmeasurable when compared to a non-paravirt_ops kernel.
At present paravirt_ops is available for x86_32, x86_64 and ia64 architectures.
Dom0 means the first guest that Xen boots. It usually (mostly always) is the one that has the driver support. The other guests that are booted (HVM or PV) are called DomU.
Current state in Linux kernel and in distributions
[Updated Oct 26th 2011]
Linux 3.0 (and later) can run as guest (domU) and as host (dom0). All necessary backends (and frontends) are in the upstream kernel. Look in Roadmap in the features section to get an idea what is happening in next kernel releases.
You can also visit the history section on the story of pvops.
Starting with Linux v2.6.37 dom0 support was added and with 3.0 having the necessary backend drivers. Fedora Core 16 and Ubuntu 11.10 ship with the 3.0 kernel (or later) and the user just needs to install the hypervisor:
$yum install xen
$apt-get install xen
TODO: Verify the Ubuntu
Then reboot the machine and select Xen in the GRUB(2) menu. Also consult Category:FAQ and XenCommonProblems
Are there other distributions that have a Xen dom0 kernels available?
Yes. See this wiki page for more information: XenDom0Kernels and XenKernelFeatures
Help! I am having troubles
First of, did you look in Category:FAQ and XenCommonProblems wiki page?
Did not find anything relevant? Was it any of these:
=== I have graphics card (DRM/TTM/KMS/Xorg) related problems with the pv_ops dom0 kernel.. ===
Screen looks like a checker-board? See errors from the Radeon|Nouveau driver? If so please see the XenPVOPSDRM wiki page.
Dom0 console gets all weird and corrupted in the end of the boot process
Is the last line on the console something like Setting console screen modes and fonts ? Then you might want to disable "console-screen.sh" service from starting automatically and it should workaround the problem.
Dom0 console doesn't show any output and remains blank
Unfortunately, a patch that enables the xen dom0 kernel to use the VGA text console didn't made it into initial release of Linux 3.0.0. This patch was merged into Linux 3.1.0 and also to 3.0.2 stable update.
Maybe it is something obvious? How do I make the bootup more verbose?
If you do encounter problems, then getting as much information as possible is very helpful. If the domain crashes very early, before any output appears on the console, then booting with: earlyprintk=xen should provide some useful information. Note that earlyprintk=xen only works for domU/dom0 if you have Xen hypervisor built in debug mode! If you are running a debug build of Xen hypervisor (set "debug = y" in Config.mk in the Xen source tree), then you should get crash dumps on the Xen console. You can view those with "xm dmesg". Also, CTRL+O can be used to send SysRq (not really specific to pv_ops, but can be handy for kernel debugging).
OK, how do I add earlyprintk=xen and all that?
Edit /boot/grub/grub.conf (or /boot/grub2/grub.cfg) and make sure you have a correct grub entry to boot Xen hypervisor with dom0 kernel.
In grub.conf it's a good idea to enable all the logging options for Xen: loglvl=all guest_loglvl=all sync_console console_to_ring and for Linux pv_ops dom0 kernel: earlyprintk=xen debug loglevel=8, and set up a serial console to be able to see and capture the full boot messages from Xen and from dom0 kernel, in the case system doesn't start up properly or crashes.
For the full list of Xen bootup options, look in XenHypervisorBootOptions Here is an example:
title pv_ops dom0 debug (2.6.32.27) with serial console root (hd0,0) kernel /xen-4.0.gz dom0_mem=1024M loglvl=all guest_loglvl=all sync_console console_to_ring com1=115200,8n1 console=com1 lapic=debug apic_verbosity=debug apic=debug iommu=off module /vmlinuz-2.6.32.27 ro root=/dev/vg00/lv01 console=hvc0 earlyprintk=xen nomodeset initcall_debug debug loglevel=10 module /initrd-2.6.32.27.img
==== I got a funky serial console (IPMI/AMT, etc) - Is there more
information available how to debug and troubleshoot using a serial
console? ====
For debugging and testing you should be using a computer with a built-in serial port on the motherboard (com1), or add a PCI serial card if your motherboard lacks a built-in serial port. You can also use SOL (Serial Over Lan) for logging the Xen hypervisor and dom0 kernel messages. Most server-class machines have SOL available through their management processor or IPMI. SOL device looks like a normal serial port for the OS/Xen, but enables you to connect to the serial console over a network, through the management processor.
For more details (and examples) please see XenSerialConsole wiki page.
Nothing is helping! Help!!
Before submitting bugreports to xen-devel mailinglist please read:
- [http://wiki.xensource.com/xenwiki/Linux_30_bugs Linux 3.0 and
further bugs] that we are aware of and working on.
- This wiki page: XenParavirtOpsHelp . It lists all the
information you NEED to provide so the problem can be diagnosed and debugged!
Please mail questions/answers/patches/etc to the [http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel Xen-devel mailing list].
Roadmap
Status updates:
- Jeremy's view of the status of pv_ops dom0 kernel (June 2009):
http://lists.xensource.com/archives/html/xen-devel/2009-06/msg01193.html
- Jeremy's roadmap update (August 2009):
http://lists.xensource.com/archives/html/xen-devel/2009-08/msg00510.html
- Jeremy's status update (September 2009):
http://lists.xensource.com/archives/html/xen-devel/2009-09/msg00806.html
- Presentation by Jeremy about pv_ops dom0 kernel at Xen Summit Asia
2009 (November 2009): http://www.xen.org/files/xensummit_intel09/xensummit-asia-2009-talk.pdf
- Short update (03 December 2009):
http://lists.xensource.com/archives/html/xen-devel/2009-12/msg00190.html
- Status update (22 December 2009):
http://lists.xensource.com/archives/html/xen-devel/2009-12/msg01127.html
- Status update (03 March 2010):
http://lists.xensource.com/archives/html/xen-devel/2010-03/msg00162.html
- Status update from Xen Summit 2010 NA (April 2010):
http://www.slideshare.net/xen_com_mgr/xen-summit-amdpvopsupdate4
- Status update from Xen Summit 2011 NA (August 2011):
http://xen.org/files/xensummit_santaclara11/aug2/5_KonradW_Update_on_Linux_PVOPS.pdf
Removing the Xen Linux kernel upstream delta
Linux distributions are using xen with the Linux kernel but the Linux kernel is typically patched with support for features and enhancements which are not yet upstream. This page documents the delta with the Linux kernel and provides a detailed analysis / status update on each of the patches for each Linux distribution. The purpose of this is page is for Linux distributions to describe each patch being carried forward for their delta, analyze whether or not it can be upstreamed and if so how, see who can or will work on it, and also identify patches which can or should be dropped. The delta for Linux distributions is very similar but SUSE likely caries the largest delta, our end objective should be to distill which delta is common and identify who is working on what. There's quite a bit of patches which likely are no longer needed due to a proper replacement already being upstream or because they are no longer applicable, identifying this also needs to be done.
Distributions delta
- OpenSUSE's 13.1 kernel sources can be found at on the
[[1]] repository on the origin/openSUSE-13.1 branch. The xen specific changes are under the kernel-source/patches.xen/ directory.
- Debian testing: TBD
Upstream delta details
Feature | pvops status | current solution | remark |
---|---|---|---|
pci-guestdev | alternative mechanism is documented and exists upstream already | SUSE patch pci-guestdev | PCI passthrough |
mem-hotplug | needs verification | SUSE patch xen-mem-hotplug | Daniel Kiper will work on this on 2015 |
hypercall preemption | Being worked on | SUSE patch xen-privcmd-hcall-preemption | Luis Rodriguez will work on this |
multi page ring | Proper upstream solution obsoletes this: indirect descriptor | SUSE patches xen-*multi-page-ring | Can be nuked |
EFI | Daniel Kiper worked on this, merged upstream on 3.17-rc1 | SUSE patch xen-x86-EFI | Done |
IPV6 autoconf | Luis R. Rodriguez working on it | SUSE patch ipv6-no-autoconf | the work consists of a proper way to address adding
the root bridge block feature, and also fixing bridging code to address this early without userspace, patches are ongoing review upstream |
pvSCSI | patches posted by Jürgen Groß, queued for upstream 3.18 | SUSE patch xen3-auto-xen-drivers.diff | |
500GB+ RAM support | patches posted by Jürgen Groß | SUSE patches xen-x86_64-note-init-p2m,
xen-x86_64-unmapped-initrd |
Jürgen Groß working on this |
pvUSB | tool stack component completed, kernel component
needs to be implemented, Greg KH welcomes this |
SUSE patch xen3-auto-xen-drivers.diff | Available for anyone to work on |
user mode pvclock | Konrad Wilk will do it | SUSE patch xen-x86_64-vread-pvclock | Still being worked on |
expose ballooning limits | needs effort | SUSE patch xen-balloon-max-target | Sysfs parameter needs to be exposed, no takers yet |
retaining tasklet in netback | needs effort | SUSE patch xen-netback-kernel-threads | David Vrabel will inspect how network latency is
impacted without this, some folks have done some testing on this |
add BLKIF_OP_PACKET | needs effort | SUSE patch xen-blkif-op-packet | Luis Rodriguez will work on this |
CD-ROM command forwarding | needs effort | SUSE patch xen-blkfront-cdrom | Luis Rodriguez will work this |
CD-ROM removable media attribute | needs effort | SUSE patch xen-blkback-cdrom | Luis Rodriguez will work on this |
CD-ROM avoid takeover in HVM | needs effort | SUSE patch xen-blkfront-hvm-no-cdrom | Luis Rodriguez will work on this |
DCDBAS address translation | needs effort | SUSE patch xen-dcdbas | Need verification from Dell - Doug Warzecha
douglas_warzecha@dell.com |
netback multicall for notifications | needs effort | SUSE patch xen-netback-notify-multi | multiple notifications should not be sent one by one,
but via a multicall |
interrupt trigger mode and polarity | needs effort | SUSE patch xen-setup-gsi | Not applicable to netback anymore, can be removed |
PAT support | patches posted by Jürgen Groß | - | Especially for WC memory type, Konrad Wilk had a try,
patches have not been accepted. Some rework needed. Jürgen Groß working on it. |
fix balloon target driver to
have a logarithmic scale of hitting the 'target' |
needs effort | - | Dan and Jan talked about it and Jan posted a patch
for this some time ago. http://lists.xensource.com/archives/html/xen-devel/2008-04/msg00143.html and http://lists.xensource.com/archives/html/xen-devel/2010-06/msg01076.html |
netfront support skb coalescing | needs effort, no takers yet | - | Borrow the ideas from Netchannel2 to coalesce the
SKB's so that the backend does not have to jump all over the memory and instead can easily fetch the pages in a physical contingous manner. |
microcode update | needs effort | - | Jeremy wrote one
http://oss.oracle.com/git/kwilk/xen.git/p=kwilk/xen.git;a=commit;h=0a49ceea0d032864a72a8744c82c3786a01f34f4 but sadly the upstream maintainer (Borislav, https://lkml.org/lkml/2011/1/30/108) was not too keen. He was thinking of making grub do the microcode update, but that sounds to have run afoul of what Ingo [x86 maintainer] thinks (http://mid.gmane.org/20110525193601.GE17864@elte.hu) in a different thread. Currently only boot time loading done directly by the hypervisor via an own microcode blob is possible. Runtime loading not supported, unclear whether to do it in the kernel or by the microcode loader being Xen-aware. Konrad will send patch to Luis Rodriguez |
MTRR support | needs effort | - | Usually this is used for graphics cards, but the 10G
Myantic drivers do enable it on their PCIe MMIO space to speed up performance (sets it to Write Combine). We need to implement (or perhaps backport from 2.6.18) the Xen MTRR code. Drivers should be able to use PAT instead of MTRR. PAT should be a proper replacement and otherwise hardware would take care of this, we should ask x86 maintainers to rip out MTRR support from the kernel. What should be done is drivers that currently required MTRR support should be modified to use PAT. |
remove VM_IO vesitages | needs effort | - | Linux 3.0 has dropped most of the _PAGE_IOMAP code.
There is one usage left in xen_make_pte and it should be redo to do proper M2P and P2M without consulting the _PAGE_IOMAP flag. Potentially remove the _PAGE_IOMAP usage in the 1-1 phys code. _PAGE_IOMAP used by mmap batches code to map foreign patches. Can be done with M2P override perhaps? The PAGE_IOMAP was used to say MFN==PFN. The outstanding issue is with xenfs doing hypercall on the behest of the tools - specifically mapping memory and providing the MFN value. |
Device hotplug (MODULE_ALIAS) | needs effort | - | Konrad sent patch for hotplug upstream |
Suspend event channel
support for faster checkpointing in Remus FT |
needs effort | - | Ian poked remus folks, remus folks should fix this otherwise |
expected to be dead (under
Xen) code cannot be easily verified to indeed be dead |
needs effort | - | e.g. IOMMU, PCI ATS, PRI, and PASID, leaving the risk
of bad interaction between hypervisor and Dom0 if a new, active user of that code appears and goes unnoticed. Kconfig option would be developed and patch carried over which won't go upstream. i915 DRM driver should be fixed to not use the Intel AGP code. Intel should be working on this. Konrad will poke them. |
old hypervisor support | needs effort | - | running the pvops kernel on top of a pre-4.0.1
hypervisor (especially as Dom0) might not work. This should work. We should get folks to test this and if issues found file a bug report for it. |
blktap driver (what about blktap3?) | needs effort | - | Performance and support of all possible blktap
configurations via qemu/qdisk is to be verified. |
oprofile support | Boris Ostrovsky is working on it | - | - |
Changelog
Kernel | Features added |
---|---|
2.6.26 |
|
2.6.27 |
|
2.6.28 |
|
2.6.29 |
|
2.6.30 |
|
2.6.31 |
|
2.6.32 |
|
2.6.33 |
|
2.6.34 |
|
2.6.35 |
|
2.6.36 |
|
2.6.37 |
|
2.6.38 |
|
2.6.39 |
|
3.0 |
|
3.1 |
|
3.2 |
|
3.3 |
|
3.4 |
|
3.5 |
|
3.6 |
|
3.7 |
|
3.8 |
|
3.9 |
|
3.11 |
|
3.12 |
|
3.14 |
|
3.15 |
|
I want to build the Xen/paravirt_ops components myself
Novice
If you are using a 3.0 kernel or later, you already have it working and there is no need to compile a new kernel - unless you feel adventurous.
Expert
The top level view is that you need to:
- Get a current kernel. The latest kernel.org
kernel is generally a good choice. Or you can use the development version.
- Configure as normal; you can start with your current .config file or
use make defconfig.
- Then configure .config Xen options
- Build the kernel
- Update #configure_modules modules (optional)
- Build the Xen hypervisor
- Update services (optional)
- Update GRUB1 or GRUB2
- Reboot and run it
- Troubleshoot if necessary
Getting the mainline Linux kernel
In order to get a proper Xen mainline kernel please check: Mainline_Linux_Kernel_Configs .
Build Xen
Xen requirements for using pv_ops dom0 kernel
Xen hypervisor and tools need to have support for pv_ops dom0 kernels. In general it means:
- The ability for the Xen hypervisor to load and boot bzImage pv_ops
dom0 kernel.
- The ability for the Xen tools to use the sysfs memory ballooning
support provided by pv_ops dom0 kernel.
- Current recommended 2.6.32.x version of pvops dom0 kernel requires
new IOAPIC setup hypercall from Xen hypervisor. This means you need to have at least Xen version 4.0.1.
Using older Xen versions is known to be problematic, for example Xen 4.0.0 libraries have problems with recent 2.6.32.x kernels, making xend fail to start due to evtchn/gntdev device node creation issues. Using Xen 3.4.2 or older won't work at all, since old hypervisor versions lack the new required IOAPIC setup hypercall and boot will fail with IRQ related issues.
It's recommended to run the latest Xen 4.0.x version, at least Xen 4.0.1.
=== Which kernel image to boot as dom0 kernel from your custom built kernel source tree? ===
If you have Xen hypervisor with bzImage dom0 kernel support, ie. xen 3.4 or later version, use "linux-2.6-xen/arch/x86/boot/bzImage" as your dom0 kernel (exactly the same kernel image you use for baremetal Linux).
If you have Xen hypervisor without bzImage dom0 kernel support, ie. any official Xen release up to at least Xen 3.3.1, or most of the Xen versions shipped with Linux distributions (before 2009-03), use "linux-2.6-xen/vmlinux" as your dom0 kernel. (Note that "vmlinux" is huge, so you can also gzip it, if you want to make it a bit smaller).
Also read the previous paragraphs for other requirements.
Get your sources from the repository, something like this can be used but the exact path will change:
$ cd /usr/src $ git clone http://xenbits.xenproject.org/xen.git $ cd xen $ sudo make xen $ sudo make tools $ sudo make install-xen $ sudo make install-tools
If you encounter any error NOT related to deps report them to
xen-devel, if you need help compiling you will find help in xen-users.
At the end in dist folder you will find xen.gz follow that symlink to
your real image.
Update services
The Ubuntu way to register a service is this:
$ sudo update-rc.d xendomains defaults 21 20
For Red Hat use chkconfig
For RC16 use systemctl:
$ sudo systemctl start xenstored.service
Other System Updates
The XENFS and XEN_COMPAT_XENFS config options are needed for /proc/xen support. If CONFIG_XEN_DEV_EVTCHN is compiled as a module, make sure to load the xen-evtchn.ko module or xend will not start.
You might also need to add a line to /etc/fstab. Xen 3.4.2 and newer automatically mount /proc/xen when /etc/init.d/xend is started, so no need to add xenfs mount entry to /etc/fstab on those systems:
none /proc/xen xenfs defaults 0 0
GRUB1 and GRUB2 (Booting)
Working grub.conf example with VGA text console:
title Xen 4.0, dom0 Linux kernel 2.6.32.24 root (hd0,0) kernel /boot/xen-4.0.gz dom0_mem=512M module /boot/vmlinuz-2.6.32.24 root=/dev/sda1 ro nomodeset module /boot/initrd.img-2.6.32.24
NOTE! You need to give correct root= parameter, ie. replace /dev/sda1
with your actual root device. Check your earlier grub kernel entries
for the correct option. Also you need to have the "nomodeset" option
for the time being. Check your earlier grub kernel entries for the
correct option. Its good to look at your initial kernel boot
configuration and use it as closely as possible, then modify the
40_custom file to suite your xen needs. Keep in mind that your initial
kernel might not use the /dev/sdX it can use the UUID notation, well
use it also.
Here is the content extracted from grub.cfg for a Ubuntu/Fedora Core kernel using grub2:
menuentry 'GNU/Linux, with Linux 2.6.38-8-generic' --class gnu-linux --class gnu --class os { recordfail set gfxpayload=$linux_gfx_mode insmod part_msdos insmod ext2 set root='(/dev/sda,msdos2)' search --no-floppy --fs-uuid --set=root 016e7c8a-4bdd-4873-92dd-d71171a49d6d linux /boot/vmlinuz-2.6.38-8-generic root=UUID=016e7c8a-4bdd-4873-92dd-d71171a49d6d ro quiet splash vt.handoff=7 initrd /boot/initrd.img-2.6.38-8-generic }
Compare them and you will see the similarties, on this particular system the boot device is located in /dev/sda2 yet if used in grub the system will not boot. Insted GRUB uses the UUID schema to detect the devices, that way the root argument can be passed to the linux kernel image.
Here is the contents of 40_customCompare them and you will see the similarities, on this particular system the boot device is located in /dev/sda2 yet if used in grub the system will not boot instead GRUB searches for the correct UUID and its is used in the kernel image, this can be easily detected when looking at the original ubuntu boot entry..
Here is the contents of 40_custom:
#! /sbin/sh exec tail -n +3 $0 # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. menuentry 'GNU/Linux, with Linux 2.6.32.40-pv' --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 search --no-floppy --fs-uuid --set=root 016e7c8a-4bdd-4873-92dd-d71171a49d6d set root='(/dev/sda,msdos2)' search --no-floppy --fs-uuid --set=root 016e7c8a-4bdd-4873-92dd-d71171a49d6d multiboot /boot/xen-4.2-unstable.gz module /boot/vmlinuz-2.6.32.40-pv placeholder root=UUID=016e7c8a-4bdd-4873-92dd-d71171a49d6d dom0_mem=1024 console=tty quiet splash vt.handoff=7 module /boot/initrd.img-2.6.32.40-pv }
Xen MUST be started using multiboot this will point to the image created when xen was compiles, the next module line is the linux kernel built from the kernel repository, this can be either jeremy or kernel.org, after the image you append placeholder or dummy=dummy because grub will strip the first argument from the module line. The last line is the ram drive created after the kernel.
Here is another working example grub.conf with serial console output (good for debugging since you can easily log the full kernel boot messages even if it crashes):
title pv_ops dom0 (2.6.32.24) with serial console root (hd0,0) kernel /xen-4.0.gz dom0_mem=1024M loglvl=all guest_loglvl=all sync_console console_to_ring com1=19200,8n1 console=com1 module /vmlinuz-2.6.32.24 ro root=/dev/vg00/lv01 console=hvc0 earlyprintk=xen nomodeset module /initrd-2.6.32.24.img
For more information about using a serial console with Xen please check the XenSerialConsole wiki page.
Booting DomU guests
If you've built a modular kernel, then all the modules will be the same either way. Some aspects of the kernel configuration have changed:
- The console is now /dev/hvc0, so put "console=hvc0" on the kernel command line
- Disk devices are always /dev/xvdX. If you want to dual-boot a
system on both Xen and native, then it's best that use use lvm, LABEL or UUID to refer to your filesystems in your /etc/fstab.
Running
=== Troubleshooting, what to do if the custom built pv_ops dom0 kernel doesn't work/boot? ===
Make sure you read the ##troubleshooting section. It has tons of good suggestions. Also consult the XenCommonProblems or Category:FAQ pages.
Historical contents
Timeline of pvops
Xen pv_ops (domU) support has been in mainline Linux since 2.6.23 (though it is probably first usable in 2.6.24), and is the basis of all on-going Linux/Xen development (the old Xenlinux patches officially ended with 2.6.18.x-xen, though various distros have their own forward-ports of them). Latest Linux kernels (2.6.27 and newer) are good for domU use. Starting from Fedora 9 all the new Fedora distribution versions include pv_ops based Xen domU kernel. Ubuntu 10.04 ("Lucid Lynx") and Debian 6.0 ("Squeeze") also includes Xen PV domU kernel. Red Hat Enterprise Linux 6.0 also includes pvops based Xen domU kernel.
Contributing
[This is obsolete, but it might be worth reading] Lots of work has been done to close the feature gaps compared to 2.6.18-xen. Many of these have been done - but there are still some left.
Devices
[Done] The Xen device model is more or less unchanged in the pv-ops kernel. Converting a driver from the xen-unstable or 2.6.18-xen tree should mostly be a matter of getting it to compile. There have been changes in the Linux device model between 2.6.18 and 2.6.26, so converting a driver will mostly be a matter of forward-porting to the new kernel, rather than any Xen specific issues.
CPU hotplug
[Done] All the mechanism should already be in place to support CPU hotplug; it should just be a matter of making it work. [2011-07-30]: It works with 3.0.
Device hotplug
[Done] In principle this is already implemented and should work. I'm not sure, however, that it's all plumbed through properly, so that hot-adding a device generates the appropriate udev events to cause devices to appear.
Device unplug/module unload
[Done] The 2.6.18-xen patches don't really support device unplug (and driver module unload), mainly because of the difficulties in dealing with granted pages. This should be fixed in the pvops kernel. The main thing to implement is to make sure that on driver termination, rather than freeing granted pages back into the kernel heap, they should be added to a list; that list is polled by a kernel thread which periodically tries to ungrant the pages and return them to the kernel heap if successful.
Development of PVOOPS in Ingo's tree
[This is obsolete, but it might be worth reading]
All x86 Xen/pv-ops changes queued for upstream Linus are in Ingo Molnar's [http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=summary tip.git] tree. You can get general information about fetching and using this tree in his [http://people.redhat.com/mingo/tip.git/README README]. The [http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=shortlog;h=x86/xen x86/xen] topic branch contains most of the Xen-specific work, though changes in other branches may be necessary too. Using the [http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=shortlog;h=auto-latest auto-latest] branch is the merged product of all the other topic branches.
Testing
[This is obsolete, but it might be worth reading]
Xen/paravirt_ops has not had wide use or testing, so any testing you do is extremely valuable. If you have an existing Xen configuration, then updating the kernel to a current pv-ops and trying to use it as you usually would, then any feedback on how well that works (success or failure) would be very interesting. In particular, information about:
- performance: better/worse/same?
- bugs: outright crash, or something just not right?
- missing features: what can't you live without?
Linux distribution support for pv_ops dom0 kernels
[This is obsolete, but it might be worth reading]
Fedora: Fedora 14 includes Xen 4.0.1 hypervisor and is able to run pvops dom0 kernel out-of-the-box. Fedora 14 does not ship with a dom0 capable kernel in the default distribution, but xendom0 kernel rpms are available from developer repositories. Fedora 13 and earlier versions ship with Xen 3.4.x and are not recommended for pvops dom0 usage, unless you update the Xen hypervisor to 4.0.x version. See this tutorial for more help: Fedora13Xen4Tutorial , and also check the Fedora dom0 wiki page: http://fedoraproject.org/wiki/Features/XenPvopsDom0 .
Debian: Debian 6.0 ("Squeeze") includes Xen 4.0.x hypervisor, and also dom0 capable kernel based on the pvops tree.
Other distributions: When using pvops dom0 kernel 2.6.32 or newer you need to have Xen hypervisor 4.0.1 or newer version.
2.6.32 and earlier kernels
[This is obsolete, but it might be worth reading] The kernel build process will build two kernel images: arch/x86/boot/bzImage and vmlinux. They are two forms of the same kernel, and are functionally identical. However, older versions of the Xen tools stack lack support loading bzImage files (pre-Xen 3.2), so you must use the vmlinux form of the kernel (gzipped, if you prefer).
Config files for 2.6.32
Example .config files:
64bit x86_64 (branch: xen/stable-2.6.32.x):
- 2.6.32.10: http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.10-pvops-dom0-xen-stable-x86_64
- 2.6.32.15: http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.15-pvops-dom0-xen-stable-x86_64
- 2.6.32.19: http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.19-pvops-dom0-xen-stable-x86_64
- 2.6.32.21: http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.21-pvops-dom0-xen-stable-x86_64
- 2.6.32.24: http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.24-pvops-dom0-xen-stable-x86_64
- 2.6.32.25: http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.25-pvops-dom0-xen-stable-x86_64
- 2.6.32.27: http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.27-pvops-dom0-xen-stable-x86_64
- 2.6.32.43: http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.43-pvops-dom0-xen-stable-x86_64
32bit PAE:
- xen/stable-2.6.31.x (2.6.31.6):
http://pasik.reaktio.net/xen/kernel-config/config-2.6.31.6-pvops-dom0-xen-master-x86_32
- xen/stable-2.6.32.x (2.6.32.10):
http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.10-pvops-dom0-xen-stable-x86_32
- xen/stable-2.6.32.x (2.6.32.27):
http://pasik.reaktio.net/xen/kernel-config/config-2.6.32.27-pvops-dom0-xen-stable-x86_32
Those kernel configs are based on Fedora 11/12 kernel configuration, with some modifications. They've been tested to work on multiple systems. Note that these .config files have various debugging options enabled which will decrease performance so don't use these .config files for performance testing!