Xen 4.2 Release Notes: Difference between revisions

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{{Warning|This is a draft of the Xen 4.2 release notes. Xen 4.2 is not yet released.}}

= Overview =
= Overview =

* Xen 4.2.0 was released on 17 September 2012. Announcement on xen.org blog: http://blog.xen.org/index.php/2012/09/17/xen-4-2-0-released/ and on xen-devel mailinglist: http://lists.xen.org/archives/html/xen-devel/2012-09/msg01271.html .
* Xen 4.2.1 was released on 18 December 2012. Announcement on xen.org blog: http://blog.xen.org/index.php/2012/12/18/xen-4-2-1-and-4-1-4-released/ and on xen-devel mailinglist: http://lists.xen.org/archives/html/xen-devel/2012-12/msg01288.html .
* Xen 4.2.2 was released on 25 April 2013. Announcement on xen.org blog: http://blog.xen.org/index.php/2013/04/25/xen-4-1-5-4-2-2-xen-document-and-xen-4-3-test-days/ and on xen-devel mailinglist: http://lists.xen.org/archives/html/xen-devel/2013-04/msg02560.html .



= New Features =
= New Features =


Xen 4.2 contains many new features and improvements to existing functionality. Changes include improvements to Security, Scalability, Performance, RAS, Documentation and to the toolstack.
High level features include:
* Security:
** Support for Intel Supervisor Mode Execution Protection (SEMP), which prevents the execution usermode of pages by the Xen hypervisor, making many application-to-hypervisor exploits much harder.
** Various Xen Security Modules ([[XSM]]) / Flask improvements. The XSM framework and the Xen Flask security module is an application of the [http://www.cs.utah.edu/flux/fluke/html/flask.html Flask] architecture to the Xen hypervisor.
* Scalability:
** Up to 256 Host CPUs for 64 bit HV
** Multiple PCI segment support
** Prefer oxenstored when present
** Also see: [[Xen 4.2 Limits]]
* Performance
** PCI pass-through for Linux Guests (see "[[Xen_4.2:_xl_and_pci_pass-through|Xen 4.2: XL and PCI pass-through]]")
** AMD SVM DecodeAssist support
** Remus memory image compression
** Scheduler improvements ('''sched_ratelimit_us''' and '''tslice_ms'''; see "[[Credit_Scheduler#Xen4.2|new commands]]" and "[[Xen_4.2:_cpupools|Xen 4.2: CPUPOOLS]]")
* Support for native EFI booting
* Libvchan cross domain comms in Xen mainline
* [[XL]] improvements
** [[XEND]] is now formally deprecated
** For a feature comparisan between [[XL]] and [[XEND]] see "[[XL vs Xend Feature Comparison]]".
* Documentation improvements (e.g. "[[Xen_Man_Pages|man pages]]", and lots of improvements to the [http://wiki.xen.org Xen wiki])
* RAS (Reliability, Availability and Serviceability):
** Enhanced Machine Check Architecture (MCA) support to include more failure types
** APEI support ([http://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface ACPI] Platform Error Interface)


A more complete list of new features and changes is available at [[Xen 4.2]]
For a list of new features and changes see [[Xen 4.2 Feature List]] and [[Xen_Release_Features|comparison of features in Xen 4.x versions]].


== Default Toolstack ==
== Default Toolstack ==


[[XL]] is now the default toolstack supplied with Xen. Please see the [[XL]] page for guidance on migrating from Xend.
[[XL]] is now the default toolstack supplied with Xen. Please see the [[XL]] page for guidance on migrating from [[XEND]].


See the [[XL_vs_Xend_Feature_Comparison]] wiki page for more information about features supported in XL vs. XM/XEND.
⚫
The previous Xend toolstack is now formally deprecated and should be expected to be removed in the 4.3 timescale. Therefore it is strongly recommended that users evaluate Xen 4.2 with [[XL]] for their use case and report any omissions or blockers such that they can be addressed for 4.3.

⚫
The [[XEND]] toolstack is now deprecated and should be expected to be removed in the 4.3 timescale. Therefore it is strongly recommended that users evaluate Xen 4.2 with [[XL]] for their use cases and report any omissions or blockers such that they can be addressed for 4.3. Fixes for serious functionality gaps will also be considered for backport to the 4.2.x releases.


= Build Requirements =
= Build Requirements =


The requirements for building Xen are documented in the <tt>README</tt> file in the Xen source tree.
The requirements for building Xen are documented in the [http://xenbits.xen.org/hg/xen-4.2-testing.hg/file/tip/README <tt>README</tt> file in the Xen source tree].


Some additional build dependencies have been added since [[Xen 4.1 Release Notes|Xen 4.1]]:
Some additional build dependencies have been added since [[Xen 4.1 Release Notes|Xen 4.1]] and [[Xen_4.0_Release_Notes|Xen 4.0]]:


* libyajl
* libyajl
Line 48: Line 31:
* markdown (optional)
* markdown (optional)


In addition Xen will now prefer to use the system wide libaio if it is available. If libaio is not installed then an intree version will be used. Users are strongly encouraged to install their distribution's version of libaio.
In addition Xen will now prefer to use the system wide <tt>libaio</tt> if it is available. If <tt>libaio</tt> is not installed then an in tree version will be used. Users are strongly encouraged to install their distribution's version of <tt>libaio</tt>.


An additional step has also been added to the build process. It is now necessary to run:
An additional step has also been added to the build process. It is now necessary to run:
Line 57: Line 40:


$ ./configure --libdir=/usr/lib64
$ ./configure --libdir=/usr/lib64

= Build instructions / tutorials =
* Information about build dependencies, required packages for common Linux distributions and building Xen from sources please see the [[Compiling_Xen_From_Source]] wiki page.

* Also a separate wiki page is available for RHEL, CentOS or Fedora users for information specific to these distributions [[Xen_4.2_Build_From_Source_On_RHEL_CentOS_Fedora]].

* Also see the [[Xen 4.1 Release Notes|Xen 4.1]] and especially [[Xen_4.0_Release_Notes|Xen 4.0]] release notes wiki pages for a list of build dependencies and required packages for rpm/deb based distros.


= Known issues =
= Known issues =


* [[XL]]'s default configuration is not compatible with driver domains. To use driver domains with [[XL]] you should set <tt>run_hotplug_scripts=0</tt> in <tt>/etc/xen/xl.conf</tt>.
⚫
[[Category:Xen]] [[Category:Release Notes]] [[Category:Users]] [[Category:Beginners]]

* On systems running a 32-bit hypervisor <tt>xl info</tt> will report incorrectly report large values for <tt>sharing_used_memory</tt> and <tt>sharing_freed_memory</tt>. Memory sharing is not supported on the 32-bit hypervisor and these should read zero.

* When using XL toolstack and "dom0_mem=" option for Xen hypervisor in grub you need to disable xl autoballoon in xl.conf, otherwise launching VMs will fail with errors about not being able to balloon down dom0. So add "autoballoon=0" to xl.conf if you have dom0_mem= option specified for Xen. Also see http://wiki.xen.org/wiki/Xen_Best_Practices#Xen_dom0_dedicated_memory_and_preventing_dom0_memory_ballooning .

⚫
[[Category:Xen]] [[Category:Xen 4.2]] [[Category:Release Notes]] [[Category:Users]] [[Category:Beginners]]

Latest revision as of 14:45, 4 June 2013

Overview


New Features

Xen 4.2 contains many new features and improvements to existing functionality. Changes include improvements to Security, Scalability, Performance, RAS, Documentation and to the toolstack.

For a list of new features and changes see Xen 4.2 Feature List and comparison of features in Xen 4.x versions.

Default Toolstack

XL is now the default toolstack supplied with Xen. Please see the XL page for guidance on migrating from XEND.

See the XL_vs_Xend_Feature_Comparison wiki page for more information about features supported in XL vs. XM/XEND.

The XEND toolstack is now deprecated and should be expected to be removed in the 4.3 timescale. Therefore it is strongly recommended that users evaluate Xen 4.2 with XL for their use cases and report any omissions or blockers such that they can be addressed for 4.3. Fixes for serious functionality gaps will also be considered for backport to the 4.2.x releases.

Build Requirements

The requirements for building Xen are documented in the README file in the Xen source tree.

Some additional build dependencies have been added since Xen 4.1 and Xen 4.0:

  • libyajl
  • glib
  • pkg-config
  • markdown (optional)

In addition Xen will now prefer to use the system wide libaio if it is available. If libaio is not installed then an in tree version will be used. Users are strongly encouraged to install their distribution's version of libaio.

An additional step has also been added to the build process. It is now necessary to run: 

$ ./configure

before building the tools (e.g. make tools, make world, make dist etc).

As a consequence of this change Xen now defaults to installing libraries into /usr/lib by default. Users on systems which use /usr/lib64 for 64-bit libraries should use the --libdir option. e.g: 

$ ./configure --libdir=/usr/lib64

Build instructions / tutorials

  • Information about build dependencies, required packages for common Linux distributions and building Xen from sources please see the Compiling_Xen_From_Source wiki page.
  • Also see the Xen 4.1 and especially Xen 4.0 release notes wiki pages for a list of build dependencies and required packages for rpm/deb based distros.

Known issues

  • XL's default configuration is not compatible with driver domains. To use driver domains with XL you should set run_hotplug_scripts=0 in /etc/xen/xl.conf.
  • On systems running a 32-bit hypervisor xl info will report incorrectly report large values for sharing_used_memory and sharing_freed_memory. Memory sharing is not supported on the 32-bit hypervisor and these should read zero.
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