2018-05-03 17:19 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>: > On 03/05/2018 03:27, Wanpeng Li wrote: >> So for 1) guest->guest attacks 2) guest/ring3->host/ring3 attacks 3) >> guest/ring0->host/ring0 attacks, if IBPB is enough to protect these >> three scenarios and retpoline is not needed? > > In theory yes, in practice if you want to do that IBPB is much more > expensive than retpolines, because you'd need an IBPB on vmexit or a > cache flush on vmentry. https://lkml.org/lkml/2018/1/4/615 Retpoline is not recommended on Skylake, so we need to pay the penalty for IBPB flush on each vmexit I think. Regards, Wanpeng Li
