Xen 4.2 Feature List

This is a preliminary list of Xen 4.2 features

Other Xen Releases

See Xen Release Features for a comparison of the featureset of different Xen releases.

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 4095 Host CPUs for 64 bit hypervisor
- Up to 5TB host memory support for 64 bit hypervisor
- Up to 512 VCPUs per PV VM and 256 VCPUs per HVM VM
- Multiple PCI segment support
- Prefer oxenstored when present
Performance
- PCI pass-through for Linux Guests
- AMD SVM DecodeAssist support
- Remus memory image compression
- Scheduler improvements (sched_ratelimit_us and tslice_ms; see "new commands" and "Xen 4.2: CPUPOOLS")
EFI boot support for the 64 bit hypervisor hosts
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)

XL is now default toolstack and XEND is formally deprecated
- For a feature comparison between XL and XEND see "XL vs Xend Feature Comparison".
- lots of XL improvements, e.g.
  - More feature complete
  - Support for Network driver domains in XL
  - Improved support for PCI pass-through (see "Xen 4.2: XL and PCI pass-through")
libxl improvements
- The libxl API is now stable.
- The libxl featureset has been greatly expanded:
  - Many slow running operations can now be done asynchronously.
  - Improved event handling subsystem.
Remus compression (compression of memory image improves performance)
Prefer oxenstored when available. Oxenstored is faster, more scalable and more reliable than the C xenstored. In particular the transaction model in oxenstored does not involve taking a complete copy of the database and aborting on any (even non-conflicting) other change. For more detail on the design, implementation and a performance comparison see this paper.
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)

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 [1]

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)

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