Xen 4.7 RC test instructions

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What needs to be tested

General things:

  • Making sure that Xen 4.7 compiles and installs properly on different software configurations; particularly on distros
  • Making sure that Xen 4.7, along with appropriately up-to-date kernels, work on different hardware.

For more ideas about what to test, please see Testing Xen.

ARM Smoke Testing

If you use ARM Hardware, which is not widely available or not rackable (and thus not part of our automated test suite), please check out Xen ARM Manual Smoke Test. Helping out to manually test ARM boards (which will only take a few minutes) will guarantee that Xen 4.7 will work on the board that you use. If you want to see which boards need testing, check Xen ARM Manual Smoke Test/Results.


Getting a RC

For the expressions/examples below, set the following bash/sh/... variable to the release candidate number (e.g. one of rc1, rc2, ... )

RC="<release candidate number>" # rc1, rc2 ...

From xen.git

With a recent enough git (>=, just pull from the proper tag (4.7.0-$RC) from the main repo directly:

git clone -b 4.7.0-$RC git://xenbits.xen.org/xen.git

With an older git version (and/or if that does not work, e.g., complaining with a message like this: Remote branch 4.7.0-$RC not found in upstream origin, using HEAD instead), do the following:

git clone git://xenbits.xen.org/xen.git ; cd xen ; git checkout 4.7.0-$RC

From tarball




Instructions are available for building Xen on Linux, NetBSD, and FreeBSD

Known issues


Test instructions


  • Remove any old versions of Xen toolstack and userspace binaries (including qemu).
  • Remove any Xen-related udev files under /etc because Xen 4.7 doesn't use those anymore.
  • Download and install the most recent Xen 4.7 RC, as described above. Make sure to check the README and INSTALL for changes in required development libraries and procedures. Some particular things to note:

Once you have Xen 4.7 RC installed check that you can install a guest etc and use it in the ways which you normally would, i.e. that your existing guest configurations, scripts etc still work.

USB Support for xl

xl introduces PVUSB support as well as the following commands:


which corresponds to

 usbdev=[ "USB_SPEC_STRING", "USB_SPEC_STRING", ... ]

as outlined in the xl.cfg(5) man page. For an overview, see Xen USB Passthrough.

RTDS scheduler improvements

The RTDS scheduler was improved in the following way

  • The RTDS scheduler has been changed from a quantum-driven model to an event-driven model, which will not invoke the scheduler unnecessarily: if you use this scheduler, you may want to test your workload using the RC and check whether there are any unexpected side effects
  • Support to get/set RTDS scheduling parameters on a per-VCPU basis has been added to libxl and xl

So, for instance:

  • to see the scheduling parameters of all VCPUs of a VM use -v all
   xl sched-rtds -d vm1 -v all
   Name                        ID VCPU    Period    Budget
   vm1                          1    0       300       150
   vm1                          1    1       400       200
   vm1                          1    2     10000      4000
   vm1                          1    3      1000       500
  • to change (or check) the scheduling parameters of VCPUs 0 and 3 only, use -v
   # xl sched-rtds -d vm1 -v 0 -p 100 -b 50 -v 3 -p 300 -b 150
   # xl sched-rtds -d vm1 -v 0 -v 3
   Name                        ID VCPU    Period    Budget
   vm1                          1    0       300       150
   vm1                          1    3      1000       500

For more information and examples, see the xl manual page (search for sched-rtds).

Credit2 runqueue arrangement and hard-affinity support

Runqueue arrangement

Xen 4.7 allows one to specify how host CPUs are arranged in runqueues, within the Credit2 scheduler. Valid alternatives are core, socket, node and all. More fine grained runqueue arrangement (as in with core) means more accurate load balancing (e.g., it will deal better with hyperthreading), but also more overhead.

To make this effective (e.g., to use Credit2 per-socket runqueues) add the following to the hypervisor boot command line:

   sched=credit2 credit2_runqueue=socket

More information here (search for credit2_runqueue)

Hard-affinity support

In Xen 4.7, Credit2 supports hard-affinity. It can be set by means of the xl vcpu-pin xl subcommand. If set for a VCPU, hard-affinity restricts the set of PCPUs where such VCPU can run.

To check that it works, give to the VCPUs of a VM an hard-affinity, by doing as follows:

   # xl vcpu-pin 1 all 16-18

And then check where they actually execute, by looking at:

   # xl vcpu-list 1
   Name                                ID  VCPU   CPU State   Time(s) Affinity (Hard / Soft)
   debian.guest.osstest                 1     0   17   r--       5.3  16-18 / all
   debian.guest.osstest                 1     1   18   r--       3.3  16-18 / all

What we want is that the values in the CPU column to be (for VCPUs that are running) always within the set of PCPUs we specified.

Hotplug disk backends (drbd, iscsi, etc.) for HVM guests

If you use drbd, iscsi, nbd, or other hotplug-script-based disk backends, try them with HVM guests.

Also see

KCONFIG support

Xen 4.7 introduces the removal of core Xen Hypervisor features at compile time via KCONFIG. We expect that this functionality is initially only going to be used for security and embedded applications, primarily targeting integration via the Yocto project. Yocto integrates with Xen via its meta-virtualization layer and the xen-image-minimal build support. The Yocto project currently integrates with Xen 4.6.1 (Yocto kergoth release). We expect that Xen with KCONFIG will be integrated with upstream Yocto, once Xen 4.7.0 has been released.

If you do want to test specific aspects of this new feature before Yocto integration has completed, please send a mail to xen-devel@ and CC the maintainer (cardoe AT cardoe DOT com) for further instructions.

Specific ARM Test Instructions

Follow Xen_ARM_with_Virtualization_Extensions and Xen_ARM_with_Virtualization_Extensions#Testing

Boards and hardware we do not test in our CI Loop

Although we do have automated Test Infrastructure for the project, we only include rackable hardware into our CI Loop. We do have a mixture of Allwinner and Exynos processors in a custom chassis. If you have one of the following boards and want to ensure it runs on Xen 4.7, please make sure you run the Xen ARM Manual Smoke Test on an RC.

Boards not tested by our CI Loop: Allwinner sun6i/A31, DRA7[J6] EVM, Exynos5410, HiKey board from 96boards.org, Mustang (XC-1), OMAP5432, Renesas R-Car H2, Versatile Express and Xilinx Zynq Ultrascale MPSoC

We are also not able to include non-production servers that require a legal agreement such as an NDA into our Test Infrastructure.

ACPI support on ARM

ACPI support requires a platform with support for ACPI 6.0 (or later). Currently there is no publicly available hardware where this can be tested, with the exception of the AEMv8A Foundation Model. For more information, see

Wallclock support

Xen now exposes the wallclock time to guests. Checking the date and time in an ARM guest is all that is needed to verify this, as long as the guest doesn't run ntpdate or doesn't have access to network.

Specific x86 Test Instructions

Huge PV Domains

The Xen Project Hypervisor supports starting a Dom0 with very large memory. PV guest limit restrictions of 512GB have been removed to allow the creation of huge PV domains in the TB range via the XL command line interface.

To test, create a PV domain with >512 GB of RAM.

Intel Code and Data Prioritization (CDP)

Icon todo.png To Do:
  • This section was not written by the author of this feature. Thus there may be inaccuracies
  • Maybe some instructions on what to test and what one expects to see

Code and Data Prioritization (CDP) Technology is an extension of CAT, which is available on Intel Broadwell and later server platforms. CDP enables isolation and separate prioritization of code and data fetches to the L3 cache in a software configurable manner, which can enable workload prioritization and tuning of cache capacity to the characteristics of the workload. CDP extends Cache Allocation Technology (CAT) by providing separate code and data masks per Class of Service (COS).

For more information see:

COLO - Coarse Grain Lock Stepping

COLO or Coarse Grain Lock Stepping is an High Availability solution that builds on top of Remus.

COLO is different from traditional High Availability solutions, which are either based on instruction level lock stepping (excessive overheads) and periodic checkpointing such as Remus (high network latency, large VM checkpointing overhead). On Xen, COLO builds on top of Remus and uses a “relaxed approach to checkpointing: in other words, COLO only checkpoints if absolutely necessary, which for many use-cases provides near native performance.

The COLO Manager component is now part of Xen 4.7, while other components will eventually be part of QEMU (they can be downloaded from a specific git repository).

Test Instructions: See COLO Docs and Test Environment.

xSplice - binary patching of the hypervisor

xSplice is a Xen technology that enables to binary patch the running hypervisor with a payload file that is intended to primarily contain security updates (but not necessarily only so). v1 of xSplice is in technology preview mode and compile-disabled by default. It also has some restrictions on what payloads can be encoded in the payload file, most notably support to generate payloads against .data sections and payloads that NOP (remove) existing functions. Xen 4.7 comes with built in Hypervisor support and the xen-xsplice upload|apply|replace|revert tool to manage payloads (the code is in tools/misc). Additional tools such as xsplice-build to create a payload are at this stage not shipped with Xen, but are available out-of-tree.

To test xSplice, check out:

Major restrictions:

  • Works for Linux and FreeBSD dom0's only
  • Does not yet work on the ARM architecture
  • Cannot generate payloads for patches with .data sections in the ELF file (in other words, patches that introduce global or static variables cannot be encoded)
  • Cannot generate payloads that remove (NOP) functions from the hypervisor

RC specific things to test


  • XSM and driver domain: start xl devd in driver domain, and see if there is XSM denial message shown in xl dmesg.

Reporting Bugs (& Issues)

  • Use Freenode IRC channel #xentest to discuss questions interactively
  • Report any bugs / missing functionality / unexpected results.
  • Please put [TestDay] into the subject line
  • Also make sure you specify the RC number you are using
  • Make sure to follow the guidelines on Reporting Bugs against Xen (please CC the relevant maintainers and the Release Manager - wei dot liu2 at citrix dot com).

Reporting success

We would love it if you could report successes by e-mailing xen-devel@lists.xen.org, preferably including:

  • Hardware: Please at least include the processor manufacturer (Intel/AMD). Other helpful information might include specific processor models, amount of memory, number of cores, and so on
  • Software: If you're using a distro, the distro name and version would be the most helpful. Other helpful information might include the kernel that you're running, or other virtualization-related software you're using (e.g., libvirt, xen-tools, drbd, &c).
  • Guest operating systems: If running a Linux version, please specify whether you ran it in PV or HVM mode.
  • Functionality tested: High-level would include toolstacks, and major functionality (e.g., suspend/resume, migration, pass-through, stubdomains, &c)

The following template might be helpful: should you use Xen 4.7.0-<Some RC> for testing, please make sure you state that information!

Subject: [TESTDAY] Test report
* Hardware:
* Software:

* Guest operating systems:

* Functionality tested:

* Comments:

For example:

Subject: [TESTDAY] Test report
* Hardware: 
Dell 390's (Intel, dual-core) x15
HP (AMD, quad-core) x5
* Software: 
Ubuntu 10.10,11.10
Fedora 17

* Guest operating systems:
Windows 8
Ubuntu 12.10,11.10 (HVM)
Fedora 17 (PV)

* Functionality tested:

* Comments:
Window 8 booting seemed a little slower than normal.

Other than that, great work!