On 12/23/09 3:36 PM, Avi Kivity wrote: > On 12/23/2009 06:44 PM, Gregory Haskins wrote: >> >>> - Are a pure software concept >>> >> By design. In fact, I would describe it as "software to software >> optimized" as opposed to trying to shoehorn into something that was >> designed as a software-to-hardware interface (and therefore has >> assumptions about the constraints in that environment that are not >> applicable in software-only). >> >> > > And that's the biggest mistake you can make. Sorry, that is just wrong or you wouldn't have virtio either. > Look at Xen, for > instance. The paravirtualized the fork out of everything that moved in > order to get x86 virt going. And where are they now? x86_64 syscalls > are slow since they have to trap to the hypervisor and (partially) flush > the tlb. With npt or ept capable hosts performance is better for many > workloads on fullvirt. And paravirt doesn't support Windows. Their > unsung hero Jeremy is still trying to upstream dom0 Xen support. And > they get to support it forever. We are only talking about PV-IO here, so not apples to apples to what Xen is going through. > > VMware stuck with the hardware defined interfaces. Sure they had to > implement binary translation to get there, but as a result, they only > have to support one interface, all guests support it, and they can drop > it on newer hosts where it doesn't give them anything. Again, you are confusing PV-IO. Not relevant here. Afaict, vmware, kvm, xen, etc, all still do PV-IO and likely will for the foreseeable future. -Greg
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