From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE863C4363A for ; Mon, 5 Oct 2020 18:48:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7950020B80 for ; Mon, 5 Oct 2020 18:48:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729165AbgJESsn (ORCPT ); Mon, 5 Oct 2020 14:48:43 -0400 Received: from mga04.intel.com ([192.55.52.120]:6073 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725940AbgJESsm (ORCPT ); Mon, 5 Oct 2020 14:48:42 -0400 IronPort-SDR: 7zcPUNdQjXrXvJPuSiRRSbLjR0qMtGvOzFRAv8upB209E2ULv30Zwpy433O2nK3gcjPX23Nmzt AMU5wCDafiMQ== X-IronPort-AV: E=McAfee;i="6000,8403,9765"; a="161223978" X-IronPort-AV: E=Sophos;i="5.77,340,1596524400"; d="scan'208";a="161223978" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Oct 2020 11:48:36 -0700 IronPort-SDR: pwdHY0+Clex6uhiQvof1tlh+ZaTorD5tBhzBp13QuXfmQhYbhxrk1rlflHdcUNlRaW+BpzA2ca mig0mG0rW8rw== X-IronPort-AV: E=Sophos;i="5.77,340,1596524400"; d="scan'208";a="516318049" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.160]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Oct 2020 09:37:48 -0700 Date: Mon, 5 Oct 2020 09:37:44 -0700 From: Sean Christopherson To: Vitaly Kuznetsov Cc: Tianjia Zhang , Paolo Bonzini , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86: filter guest NX capability for cpuid2 Message-ID: <20201005163743.GE11938@linux.intel.com> References: <20201005145921.84848-1-tianjia.zhang@linux.alibaba.com> <87ft6s8zdg.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87ft6s8zdg.fsf@vitty.brq.redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 05, 2020 at 05:29:47PM +0200, Vitaly Kuznetsov wrote: > Tianjia Zhang writes: > > > Original KVM_SET_CPUID has removed NX on non-NX hosts as it did > > before. but KVM_SET_CPUID2 does not. The two should be consistent. > > > > Signed-off-by: Tianjia Zhang > > --- > > arch/x86/kvm/cpuid.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > > index 3fd6eec202d7..3e7ba2b11acb 100644 > > --- a/arch/x86/kvm/cpuid.c > > +++ b/arch/x86/kvm/cpuid.c > > @@ -257,6 +257,7 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu, > > goto out; > > } > > > > + cpuid_fix_nx_cap(vcpu); > > kvm_update_cpuid_runtime(vcpu); > > kvm_vcpu_after_set_cpuid(vcpu); > > out: > > I stumbled upon this too and came to the conclusion this is > intentional, e.g. see this: > > commit 0771671749b59a507b6da4efb931c44d9691e248 > Author: Dan Kenigsberg > Date: Wed Nov 21 17:10:04 2007 +0200 > > KVM: Enhance guest cpuid management > > ... > > [avi: fix original KVM_SET_CPUID not removing nx on non-nx hosts as it did > before] > > but this is a very, very old story. Doesn't mean it's bogus though :-) _If_ we want to extend this behavior to KVM_SET_CPUID2, there should be a justified need.