On Fri, 9 Mar 2018, Vitaly Kuznetsov wrote: > Enlightened VMCS is just a structure in memory, the main benefit > besides avoiding somewhat slower VMREAD/VMWRITE is using clean field > mask: we tell the underlying hypervisor which fields were modified > since VMEXIT so there's no need to inspect them all. > > Tight CPUID loop test shows significant speedup: > Before: 18890 cycles > After: 8304 cycles > > Static key is being used to avoid performance penalty for non-Hyper-V > deployments. Tests show we add around 3 (three) CPU cycles on each > VMEXIT (1077.5 cycles before, 1080.7 cycles after for the same CPUID > loop on bare metal). We can probably avoid one test/jmp in vmx_vcpu_run() > but I don't see a clean way to use static key in assembly. STATIC_JUMP_IF_TRUE, STATIC_JUMP_IF_FALSE are your friends. Thanks, tglx
