On 18/12/2017 18:17, Vitaly Kuznetsov wrote: > The original author of these patches does no longer work at Red Hat, I > agreed to take this over and send upstream. Here is his original > description: > > "Makes KVM implement the enlightened VMCS feature per Hyper-V TLFS 5.0b. > I've measured about %5 improvement in cost of a nested VM exit (Hyper-V > enabled Windows Server 2016 nested in KVM)." Can you try reproducing this and see how much a simple CPUID loop costs in: * Hyper-V on Hyper-V (with enlightened VMCS, as a proxy for a full implementation including the clean fields mask) * Hyper-V on KVM, with and without enlightened VMCS The latest kvm/queue branch already cut a lot of the cost of a nested VM exit (from ~22000 to ~14000 clock cycles for KVM on KVM), so we could also see if Hyper-V needs shadowing of more fields. > This is just an initial implementation. By leveraging clean fields mask > we can further improve performance. I'm also interested in implementing > the other part of the feature: consuming enlightened VMCS when KVM is > running on top of Hyper-V. I'm also interested in consuming enlightened VMCS on Hyper-V if that can provide better performance for KVM on Azure. Paolo _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
