Xen Project Release Features
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| Xen 4.0 | Xen 4.1 | Xen 4.2 | |
|---|---|---|---|
| Initial Release | 7 April 2010 | 25 March 2011 | 17 September 2012 |
| Host Limits | |||
| Physical CPUs | 128 [ 0 ] | >255 | 4095 |
| Physical RAM | 1TB | 5TB | 5TB |
| Guest Types | |||
| Paravirtualised Traditional Xen PV guest |
✓ | ✓ | ✓ |
| HVM Guest [ 1 ] Fully virtualised guest using hardware virtualisation extensions |
✓ | ✓ | ✓ |
| PV-on_HVM Guest [ 1 ] Fully virtualised guest using PV extensions/drivers for improved performance |
✓ | ✓ | ✓ |
| PV Guest Limits | |||
| Virtual CPUs | 128 | >255 | 512 |
| Virtual RAM | 512GB | 512GB | 512GB |
| HVM Guest Limits | |||
| Virtual CPUs | 128 | 128 | 256 |
| Virtual RAM | 1TB | 1TB | 1TB |
| Toolstack | |||
| xend / xm | ✓ | ✓ | ✓deprecated in this release |
| XL | ✓initial implementation | ✓preview release | ✓ |
| Features | |||
| Live Migration, Save & Restore | ✓ | ✓ | ✓ |
| Memory ballooning | ✓ | ✓ | ✓ |
| Blktap2 | ✓ | ✓ | ✓ |
| PCI Passthrough | ✓ | ✓ | ✓ |
| TMEM -- Transcendent Memory | ✓ [ 2 ] | ✓ [ 2 ] | ✓ [ 2 ] |
| gdbsx debugger to debug ELF guests |
✓ | ✓ | ✓ |
| Memory Sharing allow sharing of identical pages between HVM guests |
✓tech preview | ✓tech preview | ✓tech preview [ 3 ] |
| Memory Paging allow pages belonging to HVM guests to be paged to disk |
✓tech preview | ✓tech preview | ✓tech preview [ 3 ] |
| Online resize of virtual disks | ✓ | ✓ | ✓ |
| Remus Fault Tolerance | ✓ | ✓ | ✓ |
| Physical CPU Hotplug | ✓ | ✓ | ✓ |
| Physical Memory Hotplug | ✓ | ✓ | ✓ |
| Support for PV kernels in bzImage format | ✓ | ✓ | ✓ |
| Credit 2 Scheduler designed for latency-sensitive workloads and very large systems. |
✓prototype | ✓prototype | |
| 1GB/2MB super page support | ✓ | ✓ | |
| x86 Advanced Vector eXtension (AVX) | ✓ [ 4 ] | ✓ [ 4 ] | |
| cpupool advanced partitioning |
✓ | ✓ | |
| memaccess API enabling integration of 3rd party security solutions into Xen virtualized environments |
✓ | ✓ | |
| Deliver events to PVHVM guests using event channels | ✓ | ✓ | |
| HVM PXE Stack | gPXE | iPXE | iPXE |
| xentrace performance analysis |
✓ | ✓ | ✓ |
| qemu based disk backend (qdisk) for XL |
✓ [ 5 ] | ✓ [ 5 ] | |
| FLASK mandatory access control policy providing fine-grained controls over Xen domains, similar to SELinux |
✓ | ✓ | ✓ |
| vPMU Virtual Power Management Unit for HVM guests |
✓ | ✓ | ✓ |
| vMCE Forward Machine Check Exceptions to Appropriate guests |
? | ? | ✓ |
| Nested Virtualisation Running a hypervisor inside an HVM guest |
✓ | ||
| Device Models and Virtual Firmware for HVM guests | |||
| Traditional Device Model Device emulator based on Xen fork of Qemu |
✓ | ✓ | ✓ |
| Qemu Upstream Device Model Device emulator based on upstream Qemu |
✓ | ||
| ROMBIOS BIOS used with traditional device model only |
✓ | ✓ | ✓ |
| SeaBIOS BIOS used with upstream qemu device model and XL only |
✓ | ||
| OVMF/Tianocore UEFI Firmware used with upstream qemu device model and XL only |
✓ | ||
| PV Bootloader support | |||
| PyGrub support for GRUB 2 | ✓ | ✓ | ✓ |
| PyGrub support for /boot on ext4 | ✓ | ✓ | ✓ |
| pvnetboot support Bootloader supporting network boot of PV guests |
✓ | ||
| Third Party | |||
| libvirt driver for XL | ✓ | ✓ | |
[ 0 ] Compile time limit, can be increased
[ 1 ] Requires hardware virtualisation support
[ 2 ] Ddisabled by default (enable with hypervisor command line option). Not supported in production and doesn't have full security support
[ 3 ] Preview, due to limited tools support. Hypervisor side in good shape
[ 4 ] Disabled by default (enable with hypervisor command line option)
[ 5 ] Used as a fallback if blkback and/or blktap2 are not available
