Xen 4.2 Feature List

This is a preliminary list of Xen 4.2 features

High Level features

• 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 Flask architecture to the Xen hypervisor.
• Scalability:
  • Increased VM density for VDI use-cases
  • up to 256 Host CPUs for 64 bit hypervisor
  • Up to 5TB host memory support for 64 bit hypervisor
  • Up to xyz VCPUs per VM
  • Multiple PCI segment support
  • Prefer oxenstored when present
• Performance
  • PCI pass-through for Linux Guests
  • AMD SVM DecodeAssist support
  • Remus memory image compression
  • New scheduler parameters [1]
• EFI boot support for the 64 bit hypervisor hosts
• Libvchan cross domain comms in Xen mainline
• XL improvements, XEND is formally deprecated
• Documentation improvements (e.g. man pages)
• RAS:
  • Enhanced MCA support to include more failure types
  • APEI support (ACPI Platform Error Interface)

Detailed List

General

• Documentation improvements (e.g. man pages)
• Lots of bug fixing of course.

Tools

• xl is now default toolstack and xend is formally deprecated
  • lots of xl improvements, e.g.
    • Support for Network driver domains in xl
  • we should highlight xend deprecation (not effectively maintained since 2008)
• Remus compression (compression of memory image improves performance)
• Prefer oxenstored when available (improves scalability!)
• Support for upstream qemu; nearing feature parity (non default still, but we want people to be testing it)
• Added libvchan to xen mainline(cross domain comms)

Xen

• Improvements to paging and sharing, enabling higher VM density for VDI use-cases
• EFI (extensible Firmware Interface) support for HV (i.e. if I have a machine that has EFI, I can use Xen on it)
• Support up to 256 Host CPUs for 64 bit h/v (from 128)
• Support dom0 kernels compressed with xz
• Per-device interrupt remapping (increases scalability)
• Support for pvhvm guest direct pirq injection (Performance improvement for PCI passthrough for Linux Guests)
• Intel SMEP (Supervisor Mode Execution Protection) support
• Mem event stuff? (Allows to externally observe what guests are up to and can be used for external virus checking - not sure what the right terminology is)
• Multiple PCI segment support
• Added xsave support(floating point)
• Lots of XSM / Flask fixes (security)
• AMD SVM "DecodeAssist" support (AMD CPU feature that avoids emulation and increases performance)
• RAS:
  • Enhanced MCA support to include more failure types
  • APEI support (ACPI Platform Error Interface)
• New scheduler parameters [2]

Removed Functionality

• ACM (alternative XSM to Flask) was removed (unmaintained)
• Removed vnet (unmaintained)
• The IA64 port was removed (unmaintained)

Xen Development Support

• Can build with clang
• Added "make deb" target
• Lots of xentrace improvements
• update ocaml bindings and make them usable by xapi (which previously had it's own fork of the same codebase)

Also See

• Category:Xen 4.2 - Contains articles and tutorials related to new functionality in Xen 4.2