2018-01-16 1:30 GMT+08:00 Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>: > Early RFC. I'll refer to this patchset in my DevConf/FOSDEM > presentations. > > When running nested KVM on Hyper-V it's possible to use so called > 'Enlightened VMCS' and do normal memory reads/writes instead of > doing VMWRITE/VMREAD instructions. Tests show that this speeds up > tight CPUID loop almost 3 times: > > Before: > ./cpuid_tight > 20459 > > After: > ./cpuid_tight > 7698 Maybe you can apply a similar idea to kvm nested on kvm. Regards, Wanpeng Li > > checkpatch.pl errors/warnings and possible 32bit brokenness are known > things. > > Main RFC questions I have are: > - Do we want to have this per L2 VM or per L1 host? > - How can we achieve zero overhead for non-Hyper-V deployments? Use static > keys? But this will only work if we decide to do eVMCS per host. > - Can we do better than a big switch in evmcs_read()/evmcs_write()? And > probably don't use 'case' defines which checkpatch.pl hates. > > I would really apreciate any feedback! > > Ladi Prosek (1): > x86/kvm: rename HV_X64_MSR_APIC_ASSIST_PAGE to > HV_X64_MSR_VP_ASSIST_PAGE > > Vitaly Kuznetsov (5): > x86/hyper-v: define virtual processor assist page structure > x86/hyper-v: allocate and use hv_vp_assist_pages > x86/hyper-v: define struct hv_enlightened_vmcs and clean field bits > x86/hyper-v: detect nested features > x86/kvm: use enlightened VMCS when running on Hyper-V > > arch/x86/hyperv/hv_init.c | 35 ++- > arch/x86/include/asm/mshyperv.h | 3 + > arch/x86/include/uapi/asm/hyperv.h | 223 +++++++++++++- > arch/x86/kernel/cpu/mshyperv.c | 3 + > arch/x86/kvm/hyperv.c | 8 +- > arch/x86/kvm/lapic.h | 2 +- > arch/x86/kvm/vmx.c | 595 ++++++++++++++++++++++++++++++++++++- > arch/x86/kvm/x86.c | 2 +- > 8 files changed, 857 insertions(+), 14 deletions(-) > > -- > 2.14.3 >
