Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752191AbdGLSEN convert rfc822-to-8bit (ORCPT ); Wed, 12 Jul 2017 14:04:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38872 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750977AbdGLSEL (ORCPT ); Wed, 12 Jul 2017 14:04:11 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 4862D7CE0F Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=bsd@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 4862D7CE0F From: Bandan Das To: Radim =?utf-8?B?S3LEjW3DocWZ?= Cc: Jim Mattson , David Hildenbrand , kvm list , Paolo Bonzini , LKML Subject: Re: [PATCH v4 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor References: <20170710204936.4001-1-bsd@redhat.com> <20170710204936.4001-4-bsd@redhat.com> <2d50ebc4-9328-ce08-b55b-6a331ee13cc3@redhat.com> <20170711191334.GB3442@potion> <20170711202227.GC3442@potion> <20170712134105.GG3326@potion> Date: Wed, 12 Jul 2017 14:04:08 -0400 In-Reply-To: <20170712134105.GG3326@potion> ("Radim \=\?utf-8\?B\?S3LEjW3DocWZ\?\= \=\?utf-8\?B\?Iidz\?\= message of "Wed, 12 Jul 2017 15:41:05 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 12 Jul 2017 18:04:11 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1061 Lines: 20 Radim Krčmář writes: ... >> > Thanks, we're not here to judge the guest, but to provide a bare-metal >> > experience. :) >> >> There are certain cases where do. For example, when L2 instruction emulation >> fails we decide to kill L2 instead of injecting the error to L1 and let it handle >> that. Anyway, that's a different topic, I was just trying to point out there >> are cases kvm does a somewhat policy decision... > > Emulation failure is a KVM bug and we are too lazy to implement the > bare-metal behavior correctly, but avoiding the EPTP list bug is > actually easier than introducing it. You can make KVM simpler and > improve bare-metal emulation at the same time. We are just talking past each other here trying to impose point of views. Checking for 0 makes KVM simpler. As I said before, a 0 list_address means that the hypervisor forgot to initialize it. Feel free to show me examples where the hypervisor does indeed use a 0 address for eptp list address or anything vm specific. You disagreed and I am fine with it.