From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] KVM : Fix read/write to IA32_FEATURE_CONTROL MSR in nested virt Date: Thu, 4 Jul 2013 14:31:25 +0300 Message-ID: <20130704113125.GJ5113@redhat.com> References: <1372858868-24755-1-git-send-email-yzt356@gmail.com> <51D51D79.8050000@redhat.com> <20130704071034.GI32123@redhat.com> <51D555FB.10305@redhat.com> <20130704111235.GI5113@redhat.com> <51D55ACF.8070702@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Arthur Chunqi Li , kvm@vger.kernel.org, jan.kiszka@web.de To: Paolo Bonzini Return-path: Received: from mx1.redhat.com ([209.132.183.28]:62708 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753041Ab3GDLb2 (ORCPT ); Thu, 4 Jul 2013 07:31:28 -0400 Content-Disposition: inline In-Reply-To: <51D55ACF.8070702@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Jul 04, 2013 at 01:21:51PM +0200, Paolo Bonzini wrote: > Il 04/07/2013 13:12, Gleb Natapov ha scritto: > > > I don't like that it requires a firmware change in order to use nested > > > VMX (at least for hypervisors that read the MSR). "Worse emulation" and > > > "better emulation + new firmware" are indistiguishable from the point of > > > view of anyone except the firmware. > > > > > > IMO there is no reason for a better emulation that no one would care > > > about _and_ could look like a regression when updating to a newer kernel. > > > > That is why now is the good time to do that since nested vmx is not > > widely used. When it will be widely used the change will be impossible > > to do for reason you age giving. So it is now or never. > > I think it is a can of worms. For example, should this be > conditionalized on running under QEMU? Under UEFI, TianoCore should be > doing it, not SeaBIOS. And for CoreBoot, should it be done by CoreBoot > or SeaBIOS? (How do people use KVM together with CoreBoot?) > This is not the first thing that firmware need to initialize. I let firmware guys fight over who is doing it, we just model HW. FWIW for Seabios patch would be trivial. > So I still prefer never... :) > This is a "can of worms" IMO. What we decide to init in KVM next to relieve firmware from its duty? This is "other hypervisor" way, in KVM we just model HW. -- Gleb.