2017-01-20 18:09+0100, Paolo Bonzini: > On 20/01/2017 17:55, Jim Mattson wrote: >> Why attempt to emulate these instructions at all, if we're not going >> to handle a data access to emulated/special memory? >> >> It seems that one of the following three cases must hold: >> >> 1) The data accessed by the instruction is emulated/special memory. >> 2) The instruction was fetched from emulated/special memory. >> 3) The instruction has been modified since the VM-exit. > > 4) The processor is in big real mode and you don't have unrestricted > guest support in your processor (or you disabled EPT). What about marking instructions that are not expected to access emulated memory? For now, we could WARN_ONCE if they do, which would pave a way to make unrestricted guest mandatory. Then we would drop instructions that were not needed with the hope that they won't be. (This would imply mandatory EPT. Also a benefit, IMO.) Westmere (the architecture to introduce unrestricted guest) is from 2010, which makes it close to being endangered by expired extended warranties. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
