Slide deck for the Ubuntu Developer's Summit 2012 Xen session.

1. Xen in Ubuntu Raring

2. Agenda
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Brief overview of Xen
●
What's new in 4.2
●
What's coming in 4.3
●
What is a great Ubuntu Xen experience?
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Integration issues
– Qemu
– Libvirt
●
Other improvements
2

3. Xen Overview

4. Basic Xen Concepts
Control Domain aka Dom0
XL, XM (deprecated) • Dom0 kernel with drivers
• Xen Management Toolstack
VMn • Trusted Computing Base
VM1
Guest Domains
Control domain One or more VM0
(dom0) driver, stub or
• Your apps
service domains Guest OS
and Apps
• E.g. your cloud management stack
Dom0 Kernel
Driver/Stub/Service Domain(s)
Scheduler, MMU Xen Hypervisor • A “driver, device model or control
Host HW
service in a box”
I/O Memory CPUs
• De-privileged and isolated
• Lifetime: start, stop, kill
4

5. PV Domains & Driver Domains
Control domain Guest VMn Driver Domain
Linux PV guests have limitations:
(dom0) e.g. • limited set of virtual hardware
Apps • Disk
• Network
PV Back Ends PV Front Ends PV Back End
Advantages
• Fast
HW Drivers HW Driver • Works on any system
Guest OS Dom0 Kernel*
(even without virt extensions)
Driver Domains
Xen Hypervisor
• Security
Host HW • Isolation
I/O Memory CPUs
• Reliability and Robustness
*) Can be MiniOS
5

6. HVM & Stub Domains
Dom0 Guest VMn Stubdomn Guest VMn
Disadvantages
• Slower than PV due to Emulation
(mainly I/O devices)
IO Emulation IO Emulation
Device Model Device Model
Advantages
IO Event
• Install the same way as native Linux
IO Event VMEXIT Mini OS VMEXIT Stub Domains
• Security
Xen Hypervisor • Isolation
• Reliability and Robustness
Host HW
6

7. Xen 4.2 and 4.3

8. Xen 4.2 Release
●
xl default toostack
●
libxl stable interface
●
xend deprecated
●
Scalability
●
4095 host CPUs, 5TiB RAM
●
cpupools for more flexible partitioning
●
Scheduler, NUMA improvements
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Security improvements
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http://wiki.xen.org/wiki/Xen_4.2_Feature_List

9. Who writes Xen?

10. Xen 4.3 Release
• Slated for 17 June 2013
• ARM server port
• “PVH” mode: PV with some HVM extensions
• NUMA
• Numerous I/O path improvements
• Qemu upsteam
• Roadmap: http://wiki.xen.org/wiki/Xen_Roadmap/4.3

11. Xen and Ubuntu

12. Integration: qemu
• Debian developments
●
Qemu-dm: Xen qemu fork
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4.2: qemu-upstream missing pass-through, migration
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4.3: qemu-upstream will be default
●
Debian has already removed qemu-dm
• Solutions
●
Qemu-xen-dm package
●
Backport features

13. Integration: libvirt
• Libvirt 0.10.2 has bindings for xend, 4.1 libxl
• 4.2 libxl bindings incompatible, xend deprecated
• Options
●
Stick with 4.1 (bad)
●
Xen 4.2, but only xend bindings
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Back-port 4.2 libxl support

14. What does a great Xen on Ubuntu look like?
• As a Xen host
●
Easy to install, set up
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Reliable, good performance
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Switching between Xen and non-Xen modes
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Good integration with libvirt, &c
• As a Xen guest
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Installation
●
Reliable, good performance

15. Potential improvements
• “Xen Host” option in installer
• Make configuring Grub2 easier
• Switching between Xen / non-Xen
• Getty for PV console (hvc0)
• Xen-tools
• Guest installation?
• Keeping an eye on linux-xen perf tweaks to backport

16. Backup slides

17. Architecture Considerations
Type 1: Bare metal Hypervisor Type 2: OS ‘Hosted’
A pure Hypervisor that runs directly on the A Hypervisor that runs within a Host OS and hosts
hardware and hosts Guest OS’s. Guest OS’s inside of it, using the host OS services
to provide the virtual environment.
VMn User-level VMM VMn
VM1 User
VM1
Apps
VM0 Device Models
VM0
Guest OS Guest OS
and Apps and Apps
Host OS
Scheduler Hypervisor
Ring-0 VM Monitor
Device Drivers/Models Device Drivers “Kernel “
MMU
Host HW Host HW
I/O Memory CPUs I/O Memory CPUs
Provides partition isolation + reliability, Low cost, no additional drivers
higher security Ease of use & installation

18. A bit of fun: our ARM Build Farm
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10 Freescale i.MX53 Loco
Quickstart boards
Running Debian "armhf" with a
mainline 3.2.0 kernel
Speed up development of Xen
for Cortex A15
(avoid cross compilation)

19. Xen 4.2 Release
• Security: Intel Supervisor Mode Execution Protection, XSM / Flask
improvements
• Scalability: increased VM density for VDI use-cases, up to 256 Host CPUs for 64
bit HV , Multiple PCI segment support, prefer oxenstored
• Performance: PCI pass-through for Linux Guests, AMD SVM DecodeAssist
support, Remus memory image compression
• EFI support
• Libvchan cross domain comms in Xen mainline
• XL improvements, XEND is formally deprecated
• Documentation improvements (e.g. man pages)