On 13/07/2017 07:57, Mihai Donțu wrote: >> Actually it makes more sense for SKIP, I think, where the introspector >> is actually doing emulation? > > I'm afraid I don't undestand your question, however we were looking at > using KVM's x86 emulator rather than putting together our own, as such > software might be fun to write but they take a very long time to get > right. I'd argue that KVM's emulator has already seen a lot of > coverage. Of course! But there could be some special cases (e.g. hypercalls) where you do emulation on your own. In that case, KVMI_SET_REGS + SKIP is the right thing to do. > In the future we are looking at maybe moving away from it on Intel-s, > by way of VMFUNC and #VE. > >> But why is KVMI_SET_REGS slower than a set regs command followed by an >> action? > To be honest, we just looked at the Xen implementation which gates > writing back the registers to VMCS on them actually having been > changed. That would be possible on KVMI too. Just don't do the KVMI_SET_REGS unless the registers have changed. Paolo
