3 ms·

Stupid question: Why does Xen need to emulate x86?

by ambrop7 12y ago

peterwwillis 12y ago
tl;dr, Windows. But also various limitations of how PV or HVM hosts work. PVH fixes it so you don't need emulation in Linux, but it's a brand new feature and probably not production quality. Read this (it's not too technical) http://wiki.xen.org/wiki/Virtualization_Spectrum http://wiki.xen.org/wiki/Virtualization_Spectrum As of this writing, Xen 4.4 and Linux 3.14 have experimental support for PVH DomUs and Xen 4.5 has support for PVH Dom0s. PVH allows practically native-hardware-speed guests without any emulation.
- cthalupa 12y ago
  Completely eliminating emulation isn't always desirable, unfortunately. The problem with PVH is the forcing the use of event channels to deliver interrupts. Local APIC emulation is fully accelerated on modern processors, which is a big win for any use case that is heavy on interrupts.