Difference between revisions of "Archived/GSoC 2015"

From Xen
m (moved Archived/GSoC 2015 to GSoC 2015 over redirect)
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|Project=Xen block backend/frontend multiqueue support
|Contact=Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
The Linux kernel (and FreeBSD, Windows, etc) have ParaVirtualized (PV) drivers to perform
the I/O instead of using the emulated devices that appear in QEMU (IDE, SCSI, etc). This is
done because the emulation of the IDE drivers is quite slow - and if you dig in how it
actually is done - it is full of bit-banging registers. The PV drivers are an answer to this
and eliminate the need for emulation. The mechanism by which they work is
nicely draw out in http://wiki.xen.org/wiki/PV_Protocol
and http://www.informit.com/articles/article.aspx?p=1160234&seqNum=3
("Definitive Guide to the Xen Hypervisor, The")
There have been improvements done in it - see http://wiki.xen.org/wiki/Xen_4.3_Block_Protocol_Scalability
and http://blog.xen.org/index.php/2013/08/07/indirect-descriptors-for-xen-pv-disks/
However, there are still room for improvement. We can utilize the new
block multiqueue API support in Linux (See https://lwn.net/Articles/552904/
and http://kernel.dk/systor13-final18.pdf)
to allocate per CPU a block thread (which handles the I/O transmission).
That should provide greater throughput and lower latency for I/O workloads.
Also see https://docs.google.com/document/d/1Vh5T8Z3Tx3sUEhVB0DnNDKBNiqB_ZA8Z5YVqAsCIjuI
which has some of the explanation.
| Skills=You need to have understanding of:
* Knowledge of Linux kernel
* How I/O works
* C language
|Outcomes=Expected outcome:
* Patches for the Linux Kernel Mailing list (LKML).
* Benchmark reports.

Revision as of 14:20, 22 September 2015

Icon Info.png Unfortunately the project has not been accepted for GSoC in 2015! However, there are Xen related projects hosted in various organisations, such as

We should also be able to find mentors and add Xen related projects in the following places:

  • qemu - if you are interested, please get in touch with developers on xen-devel



Xen Project

The Xen Project is a Linux Foundation collaborative project that develops the

The project also has excellent relationships with its upstreams (Linux Kernel, the BSDs, QEMU and other projects) and upstreams such as Linux distributions. This is reflected in the project list, which contains many interesting cross-project development projects for students.

GSoC and Xen Project

This page is used to list project ideas for Google Summer of Code (GSOC) 2015.

Key GSoC resources

The Xen Project is planning to apply as a Mentoring Organization. Stay posted.

Finding a project that fits you

This page lists Xen Project development projects for GSoC that can be picked up by anyone! If you're interesting in hacking Xen Project code and want to become a part of our friendly developer community this is the place to start! Ready for the challenge?

To work on a project:

  • Find a project that looks interesting (or a bug if you want to start with something simple)
  • Send an email to the relevant mailing list (see Developer Mailing Lists) - the correct list should also be on the project - and let us know if you are interested in starting to work or applying on a specific project.
  • Post your ideas, questions, RFCs to the relevant mailing list sooner than later so you can get comments and feedback.

You have your own project idea: no problem!

  • If you have your own project idea, outline what you are trying to do on the mailing list. If you know the right list, post your project idea on mailing list. Failing that post on xen-devel and we can redirect you to the right list. Make sure you add GSoC 2015 to the subject line.

It is a good idea to ...
The Xen Project has also participated in the Gnome Outreach Program for Women (OPW) in the past. One of the things we learned by participating in OPW is that you will be more successful, happier and get more out of participating in student programs such as GSoC, if you do a bit of prep-work before writing an application. Here is some stuff you can do:

  • Contact your mentor early and get to know him or her
  • If the Xen Project is accepted into GSoC, start hanging out on our IRC channel. You can use the #xen-opw IRC channel on freenode.net for now (if accepted, we will create a GSoC channel)
  • You may want to ask the mentor for a couple of small bitesize work-items (such as reviewing someones patch, a bitesize bug, ...) and start communicating on the relevant mailing list. That helps you become familiar with our development process, the mentor and other community members and will help you chose the right project and help you decide whether the Xen project is for you.
  • Note that quite a few Xen maintainers used to be GSoC students once. Feel free to ask community dot manager at xenproject dot org to put you in touch with them if you have questions about their experience.
  • Any work you submit before applying for a project should be based on xen-unstable development tree, if the project is Xen Hypervisor and/or tools related. Linux kernel related patches should be based on upstream kernel.org Linux git tree (latest version). XAPI and Mirage OS patches should be based on the right codeline too. Check out the navigation by audience section on the left to find resources.

More Resources

Project resources are listed in below's table. Projects in the GSoC project list are under headline that maps to one of the entries below, e.g. a project under Xen Hypervisor Userspace Tools will map to the Xen Hypervisor in the table below. Also note that the links in the Sub-Project/Team column will get you to a page with general resources related to that project.

Sub-Project/Team Mailing List Code Repos Additional Information
Domain Support Start with xen-devel@lists.xenproject.org Mainline Linux Kernel Configs, Xen Project Repositories Xen Developer Wiki
Xen Hypervisor (x86 & ARM) xen-devel@lists.xenproject.org Xen Project Repositories Xen Developer Wiki, Xen Developer Wiki (ARM related info)
The XAPI toolstack xen-api@lists.xenproject.org xapi-project on GitHub XAPI Developer Wiki
Mirage OS mirageos-devel@lists.xenproject.org mirage on GitHub - you can check out all repos via git clone --recursive git://github.com/mirage/megamirage Mirage OS Developer Wiki, Mirage OS Site
Windows PV Drivers win-pv-devel@lists.xenproject.org Windows_PV_Drivers/Repositories Windows PV Drivers Developer Wiki
Embedded & Automotive Drivers embedded-pv-devel@lists.xenproject.org None yet Embedded & Automotive Drivers Developer Wiki

Aspiring Students

  • Please contact the mailing list and CC the mentor (you can find mentor e-mail addresses on the talk page). Please do *not* contact the mentor without CC'ing the list: GSoC is about community engagement and you will need to get used to working in public on the mailing list.
  • Get a bite-size task from the mentor before the application starts
  • If you feel comfortable with an idea, please put your name to an idea using the following format
|Review=(delete as addressed)
* {{Comment|~~~~:}} I am interested in this idea ... 
                    (note that you may also want to link to the e-mail thread with the mentor)
  • You will need to request write access to the wiki by filling out this form

Applying for GSoC

Icon Info.png Note that we will update this section when more student information on melange is available, to make it easier for you to find information. And of course assuming that the Xen Project will be accepted into GSoC.

To apply for a project, follow the steps outlined on

List of peer reviewed Projects

Domain support (PVOPS and Linux)

Utilize Intel QuickData on network and block path.

Date of insert: 01/22/2013; Verified: Not updated in 2020; GSoC: Yes
Technical contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: High
Skills Needed: The basic requirement for this project is Linux kernel programming skill. The candidate for this project should be familiar with open source development workflow as it may require collaboration with several parties.
Description: The Intel QuickData, also known as Direct Cache Access (or IOA/T), is the chipset that sits in the PCIe subsystem in the Intel systems. It allows the PCIe subsystem to tag which PCIe writes to memory should reside in the Last Level Cache (LLC, also known as L3, which in some cases can be of 15MB or 2.5MB per CPU). This offers incredible boosts of speed - as we bypass the DIMMs and instead the CPU can process the data in the cache.

Adding this component in the network or block backends can mean that we can keep the data longer in the cache and the guest can process the data right off the cache.

See these for references: http://www.intel.com/content/www/us/en/wireless-network/accel-technology.html http://www.intel.com/content/www/us/en/chipsets/quickdata-technology-software-guide-for-linux-paper.html

Also the dmaengine@vger.kernel.org is an excellent mailing list to subscribe to.
Outcomes: Expected outcome:
  • Investigate whether DCA (aka QuickData aka I/O AT) works with Xen.
  • If above is true: have upstream patches (or draft patches)
  • and benchmark report of with and without.

Enabling the 9P File System transport as a paravirt device

Date of insert: 01/20/2014; Verified: 02/13/2015; GSoC: Yes
Technical contact: Wei Liu <wei.liu2@citrix.com> Julien Grall <julien.grall@citrix.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: High
Skills Needed: Required skills include knowledge of kernel hacking, file system internals. Desired skills include: understanding of Xen PV driver structure, and VirtIO.
Description: VirtIO provides a 9P FS transport, which is essentially a paravirt file system device. VMs can mount arbitrary file system hierarchies exposed by the backend. The 9P FS specification has been around for a while, while the VirtIO transport is relatively new. The project would consist of implementing a classic Xen front/back pv driver pair to provide a transport for the 9P FS Protocol.
Outcomes: Expected outcome:
  • LKML patches for front and back end drivers.
  • In particular, domain should be able to boot from the 9P FS.
Peer Review Comments
(delete as addressed)
  • Pictogram voting comment 15px.png Lars.kurth 15:24, 17 February 2014 (UTC): This project would benefit from links to the virtio specs and documents explaining how the PV protocol works.

Xen Hypervisor Userspace Tools

CPU/RAM/PCI diagram tool

Date of insert: 01/30/2014; Verified: Not updated in 2020; GSoC: yes
Technical contact: Andrew Cooper <andrew.cooper3@citrix.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Moderate, to Extremely Difficult (depending on which area of the problem you choose to tackle)
Skills Needed: Understanding of PC server hardware, Understanding of ACPI/SMBios tables, Linux scripting or kernel hacking (depending on which area of the problem you choose to tackle)
Description: It is often useful in debugging kernel, hypervisor or performance problems to understand the bus topology of a server. This project will create a layout diagram for a server automatically using data from ACPI Tables, SMBios Tables, lspci output etc. This tool would be useful in general Linux environments including Xen and KVM based virtualisation systems. There are many avenues for extension such as labelling relevant hardware errata, performing bus throughput calculations etc.
Outcomes: A tool is created that can either run on a live Linux system or offline using captured data to produce a graphical representation of the hardware topology of the system including bus topology, hardware device locations, memory bank locations, etc. The tool would be submitted to a suitable open-source project such as the Xen hypervisor project or XCP.

KDD (Windows Debugger Stub) enhancements

Date of insert: 01/30/2014; Verified: 02/10/2015; GSoC: yes
Technical contact: Paul Durrant <paul.durrant@citrix.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Medium
Skills Needed: C, Kernel Debuggers, Xen, Windows
Description: kdd is a Windows Debugger Stub for Xen hypervisor. It is OSS found under http://xenbits.xen.org/gitweb/?p=xen.git;a=tree;f=tools/debugger/kdd;h=fd82789a678fb8060cc74ebbe0a04dc58309d6d7;hb=refs/heads/master

kdd allows you to debug a running Windows virtual machine on Xen using standard Windows kernel debugging tools like WinDbg. kdd is an external debugger stub for the windows kernel. Windows can be debugged without enabling the debugger stub inside windows kernel by using kdd. This is important for debugging hard to reproduce problems on Windows virtual machines that may not have debugging enabled.

Expected Results:

  1. Add support for Windows 8 (x86, x64) to kdd
  2. Add support for Windows Server 2012 to kdd
  3. Enhance kdd to allow WinDbg to write out usable Windows memory dumps (via .dump debugger extension) for all supported versions
  4. Produce a user guide for kdd on Xen wiki page
Nice to have: Allow kdd to operate on a Windows domain checkpoint file (output of xl save for e.g.)
Outcomes: Code is submitted to xen-devel@xen.org for inclusion in the xen-unstable project.

CPUID Programming for Humans

Date of insert: 02/04/2014; Verified: Not updated in 2020; GSoC: Yes
Technical contact: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Easy
Skills Needed: A good understanding of C user-land programming, and the ability to dive into qemu/libvirt (for reference code and integration), as well as libxc and libxl (for implementation).
Description: When creating a VM, a policy is applied to mask certain CPUID features. Right now it's black magic.

The KVM stack has done an excellent job of making this human-useable, and understandable.

For example, in a qemu-kvm command-line you may encounter:

-cpu SandyBridge,+pdpe1gb,+osxsave,+dca,+pcid,+pdcm,+xtpr,+tm2,+est,+smx,

And in <qemu>/target-i386.c you find a fairly comprehensive description of x86 processor models, what CPUID features are inherent, and what CPUID feature each of these symbolic flags enables.

In the Xen world, there is a libxc interface to do the same, although it's all hex and register driven. It's effective, yet horrible to use.

An ideal outcome would have libxl config files and command line absorb a similarly human-friendly description of the CPUID features a user wishes for the VM, and interface appropriately with libxl. Further, autodetection of best CPUID shuold yield a human-readable output to be able to easily understand what the VM thinks about its processor.

Finally, interfacing with libvirt should be carefully considered.

CPUID management is crucial in a heterogeneous cluster where migrations and save restore require careful processor feature selection to avoid blow-ups.


Outcomes: Expected outcome:
  • Mainline patches for libxl

Rump kernel based stubdom

Date of insert: Feb 06 2014; Verified: Feb 06 2014; GSoC: Yes
Technical contact: Wei Liu <wei.liu2@citrix.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Easy
Skills Needed: Knowledge of operating system, GNU autotools, C programming and good debugging skills.
Description: Stubdom can help boost performance and security. Currently stubdom is not very nice to work with. It employs an ancient version of newlib and the build system is fragile.

Rump kernel (a way to implement unikernel / library OS) already runs on Xen and it uses NetBSD's libraries which are much more maintainable. This project aims to port existing stubdoms (c, xenstore, ocaml etc) to rump kernel.

During this process, student can get first hand experience on Xen and rump kernel and tackle both kernel level and application level problems. The experience on the frontier of OS development and research is also valuable. Student should be able to understand how a to turn a piece of software into unikernel when he / she finishes this project.

Useful links:

Outcomes: Patches for Xen and rump kernel.


Various MirageOS Pioneer Projects

Date of insert: 01/30/2015; Verified: Feb 8th, 2015 (see this conversation); GSoC: yes, but do check mirageos-devel@lists.xenproject.org first
Technical contact: Send a mail to mirageos-devel@lists.xenproject.org if you're interested in starting on one or several of these projects.
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Various levels of difficulty
Skills Needed: OCaml
Description: This is a list of pioneer projects for Mirage OS, covering area such as Build Tools, New Libraries, Storage Technologies, Networking Technologies, Interfaces to Non-OCaml (aka foreign) Languages, Testing and other topics. Note that some of these projects may be too small or too big for a single GSoC project. If you are interested in one of these, make sure you discuss first on mirageos-devel@lists.xenproject.org - we can then merge or split these as needed for GSoC.


Outcomes: Listed in Complete list of Pioneer Projects

List of projects that need more work

Xen Hypervisor

Introducing PowerClamp-like driver for Xen

Date of insert: 01/22/2013; Verified: Not updated in 2020; GSoC: Yes
Technical contact: George Dunlap <george.dunlap@eu.citrix.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Unknown
Skills Needed: Unknown
Description: PowerClamp was introduced to Linux in late 2012 in order to allow users to set a system-wide maximum

power usage limit. This is particularly useful for data centers, where there may be a need to reduce power consumption based on availability of electricity or cooling. A more complete writeup is available at LWN.

These same arguments apply to Xen. The purpose of this project would be to implement a similar functionality in Xen, and to make it interface as well as possible with the Linux PowerClamp tools, so that the same tools could be used

for both. GSoC_2013#powerclamp-for-xen
Outcomes: Not specified, project outcomes

Xen Hypervisor Userspace Tools

Refactor Linux hotplug scripts

Date of insert: 15/11/2012; Verified: Not updated in 2020; GSoC: Yes
Technical contact: Roger Pau Monné <roger.pau@citrix.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Unknown
Skills Needed: Unknown
Description: Current Linux hotplug scripts are all entangled, which makes them really difficult to understand or modify. The reason of hotplug scripts is to give end-users the chance to "easily" support different configuration for Xen devices.

Linux hotplug scripts should be analized, providing a good description of what each hotplug script is doing. After this, scripts should be cleaned, putting common pieces of code in shared files across all scripts. A Coding style should be applied to all of them when the refactoring is finished.

Outcomes: Not specified, project outcomes

XL to XCP VM motion

Date of insert: 15/11/12; Verified: Not updated in 2020; GSoC: Yes
Technical contact: Ian Campbell
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Unknown
Skills Needed: Unknown
Description: Currently xl (the toolstack supplied alongside Xen) and xapi (the XCP toolstack) have very different concepts about domain configuration, disk image storage etc. In the XCP model domain configuration is persistent and stored in a data base while under xl domain configuration is written in configuration files. Likewise disk images are stored as VDIs in Storage Repositories while under xl disk images are simply files or devices in the dom0 filesystem. For more information on xl see XL. For more information on XCP see XCP Overview.

This project is to produce one or more command-line tools which support migrating VMs between these toolstacks.

One tool should be provided which takes an xl configuration file and details of an XCP pool. Using the XenAPI XML/RPC interface It should create a VM in the pool with a close approximation of the same configuration and stream the configured disk image into a selected Storage Repository.

A second tool should be provided which performs the opposite operation, i.e. give a reference to a VM residing in an XCP pool it should produce an XL compatible configuration file and stream the disk image(s) our of Xapi into a suitable format.

These tools could be reasonably bundled as part of either toolstack and by implication could be written in either C, Ocaml or some other suitable language.

The tool need not operate on a live VM but that could be considered a stretch goal.

An acceptable alternative to the proposed implementation would be to implement a tool which converts between a commonly used VM container format which is supported by XCP (perhaps OVF or similar) and the xl toolstack configuration file and disk image formats.

Outcomes: Not specified, project outcomes

Advanced Scheduling Parameters

Date of insert: 01/22/2013; Verified: Not updated in 2020; GSoC: Yes
Technical contact: George Dunlap <george.dunlap@eu.citrix.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Unknown
Skills Needed: Unknown
Description: The credit scheduler provides a range of "knobs" to control guest behavior, including CPU weight and caps. However,

a number of users have requested the ability to encode more advanced scheduling logic. For instance, "Let this VM max out for 5 minutes out of any given hour; but after that, impose a cap of 20%, so that even if the system is idle he can't an unlimited amount of CPU power without paying for a higher level of service."

This is too coarse-grained to do inside the hypervisor; a user-space tool would be sufficient. The goal of this project would

be to come up with a good way for admins to support these kinds of complex policies in a simple and robust way.
Outcomes: Not specified, project outcomes

PCI Pass-through improvements

Allowing guests to boot with a passed-through GPU as the primary display

Date of insert: 01/22/2013; Verified: Not updated in 2020; GSoC: Yes
Technical contact: George Dunlap <george.dunlap@eu.citrix.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Unknown
Skills Needed: Unknown
Description: One of the primary drivers of Xen in the "consumer market" of the open-source world is the ability to

pass through GPUs to guests -- allowing people to run Linux as their main desktop but easily play games requiring proprietary operating systems without rebooting.

GPUs can be easily passed through to guests as secondary displays, but as of yet cannot be passed through as primary displays. The main reason is the lack of ability to load the VGA BIOS from the card into the guest.

The purpose of this project would be to allow HVM guests to load the physical card's VGA bios, so that the guest can boot with it as the primary display.

Outcomes: Not specified, project outcomes

Improve PCIe Advanced Error Reporting (AER) handling for passed-through devices

Date of insert: 03/04/2014; Verified: Not updated in 2020; GSoC: Yes
Technical contact: Matt Wilson <msw@amazon.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Medium-High
Skills Needed: Understanding of PC server hardware, PCIe, C
Description: Today the xen-pciback driver handles an AER event for passed-through PCI devices. If the device is assigned to a PV guest, it uses xenstore to request a reset from xen-pcifront. If the device is assigned to a HVM guest, the toolstack is notified and is expected to take corrective action. The toolstack support for taking corrective action is only implemented in xend, not libxl. For HVM guests ideally, the AER event would be propagated into the guest through the device model (qemu) so that the driver inside the guest can take reset actions.
Outcomes: Patches for libxl, qemu, and perhaps xen-pciback posted


DRBD Integration

Date of insert: 07/01/2013; Verified: Not updated in 2020; GSoC: Unknown
Technical contact: John Morris <john@zultron.com>
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Unknown
Skills Needed: Unknown
Description: DRBD is potentially a great addition to the other high-availability features in XenAPI. An architecture of as few as two Dom0s with DRBD mirrored local storage is an inexpensive minimal HA configuration enabling live migration of VMs between physical hosts and providing failover in case of disk failure, and eliminates the need for external storage. This setup can be used in small shop or hobbyist environments, or could be used as a basic unit in a much larger scalable architecture.

Existing attempts at integrating DRBD sit below the SM layer and thus do not enable one VBD per DRBD device. They also suffer from a split-brain situation that could be avoided by controlling active/standby status from XenAPI.

DRBD should be implemented as a new SR type on top of LVM. The tools for managing DRBD devices need to be built into storage management, along with the logic for switching the active and standby nodes.
Outcomes: Not specified, project outcomes

New Project Ideas

Please add new project ideas here, following


GSoC Projects that were accepted in 2014

Implement Xen PVUSB support in xl/libxl toolstack

Date of insert: 01/12/2012; Verified: Not updated in 2020; GSoC: Yes
Technical contact: Mentor: George Dunlap, Student: Bo Cao
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Unknown
Skills Needed: Unknown
Description: xl/libxl does not currently support Xen PVUSB functionality. Port the feature from xm/xend to xl/libxl. Necessary operations include:
  • Task 1: Implement PVUSB in xl/libxl, make it functionally equivalent to xm/xend.
  • Send to xen-devel mailinglist for review, comments.
  • Fix any upcoming issues.
  • Repeat until merged to xen-unstable.
  • See above for PVUSB drivers for dom0/domU.
  • Xen PVUSB supports both PV domUs and HVM guests with PV drivers.
  • More info: http://wiki.xen.org/xenwiki/XenUSBPassthrough
Pictogram voting comment 15px.png Lars.kurth 14:14, 23 January 2013 (UTC): Should be suitable, but desc needs. Rate in terms of challenges, size and skill. Also kernel functionality is not yet upstreamed. Maybe Suse kernel.
Outcomes: Not specified, project outcomes

Lazy restore using memory paging

Date of insert: 01/20/2014; Verified: Not updated in 2020; GSoC: Yes
Technical contact: Mentor: Andres Lagar-Cavilla, Student: Dushyant Behl
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Medium
Skills Needed: A good understanding of save/restore, and virtualized memory management (e.g. EPT, shadow page tables, etc). In principle the entire project can be implemented in user-space C code, but it may be the case that new hypercalls are needed for performance reasons.
Description: VM Save/restore results in a boatload of IO and non-trivial downtime as the entire memory footprint of a VM is read from IO.

Xen memory paging support in x86 is now mature enough to allow for lazy restore, whereby the footprint of a VM is backfilled while the VM executes. If the VM hits a page not yet present, it is eagerly paged in.

There has been some concern recently about the lack of docs and/or mature tools that use xen-paging. This is a good way to address the problem.
Outcomes: Expected outcome:
  • Mainline patches for libxc and libxl

HVM per-event-channel interrupts

Date of insert: 01/30/2013; Verified: Not updated in 2020; GSoC: yes
Technical contact: Mentor: Paul Durrant, Student: Yandong Han
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Unknown
Skills Needed: C, some prior knowledge of Xen useful
Description: Windows PV drivers currently have to multiplex all event channel processing onto a single interrupt which is registered with Xen using the HVM_PARAM_CALLBACK_IRQ parameter. This results in a lack of scalability when multiple event channels are heavily used, such as when multiple VIFs in the VM as simultaneously under load. Goal: Modify Xen to allow each event channel to be bound to a separate interrupt (the association being controlled by the PV drivers in the guest) to allow separate event channel interrupts to be handled by separate vCPUs. There should be no modifications required to the guest OS interrupt logic to support this (as there is with the current Linux PV-on-HVM code) as this will not be possible with a Windows guest.
Outcomes: Code is submitted to xen-devel@xen.org for inclusion in xen-unstable

Mirage OS cloud API support

Date of insert: 28/11/2013; Verified: Not updated in 2020; GSoC: yes
Technical contact: Mentor: Dave Scott; Student: Jyotsna Prakash
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: medium
Skills Needed: OCaml
Description: MirageOS (see http://xenproject.org/developers/teams/mirage-os.html, http://www.openmirage.org/) is a type-safe unikernel written in OCaml which generates highly specialised "appliance" VMs that run directly on Xen without requiring an intervening kernel. A MirageOS application typically runs via several communicating kernel instances on the cloud. Today these instances are difficult to manage; we would like to explore strategies for managing these distributed computations using common public cloud APIs such as those exposed by Amazon EC2 and Rackspace.

First we need to create pure OCaml API bindings for (e.g.) EC2 and Rackspace (purity is needed to ensure portability). These API bindings can then be used to provide operating-system-level abstractions to the unikernels. For example, a traditional VM might hotplug a vCPU; while a MirageOS application would request a "VM create" using the cloud API and "connect" the new instance to the existing network. We should be able to spin up 1000s of "CPUs" by using such APIs in a cluster environment.

As well as helping Xen/Mirage, the public cloud API bindings will be very useful to other people in other contexts-- a nice side-effect.

See https://fedoraproject.org/wiki/User:Gholms/EC2_Primer for a primer on how to use EC2
Outcomes: 1. one or more public cloud API bindings plus examples, in a standalone repo on github; 2. an example mirage app which uses these APIs to spin up a new VM

Parallel xenwatch kthread

Date of insert: 01/08/2012; Verified: Not updated in 2020; GSoC: Yes
Technical contact: Mentor: Boris Ostrovsky, Student: Tülin İZER
Mailing list/forum for project: xen-devel@
IRC channel for project: #xen-devel
Difficulty: Low-Medium
Skills Needed: You need to have understanding of:
  • locks - spinlocks and mutexes
  • build Linux kernel
Description: Xenwatch is locked with a coarse lock. For a huge number of guests this represents a scalability issue. The need is to rewrite the xenwatch locking in order to support full scalability.

See https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/xen/xenbus/xenbus_xs.c#n768

for the code.
Outcomes: Expected outcome:
  • Have upstream patches or a draft of them.
  • benchmark report of with and without.

Conventions for Projects and Project Mentors

Rules and Advice for Adding Ideas

  • Be creative
  • Add projects into New Project Ideas or improve projects in Project Ideas that Need Review or more work through review comments.
  • Use the {{GSoC Project}} template to encode ideas on this page. Please read the Template Documentation before you do so.
  • Be specific: what do you want to be implemented; if at all possible provide an indication of size and complexity as described above to make it easier for a student to choose ideas
  • Check that the project meets the GSoC Program Goals
  • If you are willing to mentors those ideas, add your name and email to the idea.
  • Aspiring mentors should introduce themselves on the most appropriate Xen Project mailing list

Peer Review Goals

We strongly recommend and invite project proposers and project mentors to review each others proposals. When you review, please look out for

  • Can a student get going and started with the information in the project description
  • Are any unstated assumptions in the proposal, is there undefined terminology, etc. in the proposal
  • Can the project completed in 3 months (assume that one month is needed for preparation)
  • Does the project meet Google Summer of Code goals, which are
    • Create and release open source code for the benefit of all
    • Inspire young developers to begin participating in open source development
    • Help open source projects identify and bring in new developers and committers
    • Provide students the opportunity to do work related to their academic pursuits (think "flip bits, not burgers")
    • Give students more exposure to real-world software development scenarios (e.g., distributed development, software licensing questions, mailing-list etiquette)

Peer Review Conventions

The {{GSoC Project}} template used to encode GSoC projects, contains some review functionality. Please read the Template Documentation before you add a template, also please use the conventions below to make comments.

|Review=(delete as addressed)
* {{Comment|~~~~:}} Comment 1
* {{Comment|~~~~:}} Comment 2

Choosing Projects

We have a bi-weekly mentor meeting overlooked by our program management team, which are a core team of 2-3 mentors and a program administrator. This group will work with mentors to ensure that project proposals are of good quality and whether mentors are engaging with the program management team and students in the weeks before the application period ends.