It's been a while since RFCv1 (https://lwn.net/Articles/741846/). After the initial submission I decided to implement Enlightened VMCS for KVM on Hyper-V first and this is now fully merged. Time to resume this work. This is an initial implementation of Enlightened VMCS for nested Hyper-V on KVM. Using it helps to spare 1100 cpu cycles for nested vmexit (tight cpuid loop in WS2016 with Hyper-V role on KVM: 15200 cycles -> 14100 cycles). 'RFC' mostly goes to the last patch in the series. Currently, we have prepare_vmcs02()/prepare_vmcs02_full() split which is only valid for Shadow VMCS. Enlightened VMCS has 'clean fields' idea and I'm having hard times incorporating it. The simplest way is implemented in the patch: we just wrap groups of vmwrites with 'if (!hv_evmcs||evmcs_needs_write(vmx, ...))' checks. This works and doesn't give much overhead for non-eVMCS case (compared to e.g. wrapping each vmwrite with such check) but this is not flexible and ugly. In case we'll need to implement additional ideas later (eVMCSv2 when it comes, something similar for KVM-on-KVM,...) it will be really hard. So.. looking forward to your ideas! Ladi Prosek (1): KVM: hyperv: define VP assist page helpers Vitaly Kuznetsov (4): KVM: nVMX: add KVM_CAP_HYPERV_ENLIGHTENED_VMCS capability KVM: nVMX: add enlightened VMCS state KVM: nVMX: implement enlightened VMPTRLD and VMCLEAR KVM: nVMX: optimize prepare_vmcs02{,_full} for Enlightened VMCS case arch/x86/include/asm/kvm_host.h | 3 + arch/x86/kvm/hyperv.c | 23 +- arch/x86/kvm/hyperv.h | 4 + arch/x86/kvm/lapic.c | 4 +- arch/x86/kvm/lapic.h | 2 +- arch/x86/kvm/svm.c | 9 + arch/x86/kvm/vmx.c | 807 +++++++++++++++++++++++++++++++++------- arch/x86/kvm/x86.c | 17 +- include/uapi/linux/kvm.h | 1 + 9 files changed, 728 insertions(+), 142 deletions(-) -- 2.14.3
