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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 EBBF2C43142 for ; Tue, 31 Jul 2018 12:59:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ACB69208A6 for ; Tue, 31 Jul 2018 12:59:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ACB69208A6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732277AbeGaOjW (ORCPT ); Tue, 31 Jul 2018 10:39:22 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:59532 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732107AbeGaOjW (ORCPT ); Tue, 31 Jul 2018 10:39:22 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B42F64219DA1; Tue, 31 Jul 2018 12:59:08 +0000 (UTC) Received: from [10.36.117.153] (ovpn-117-153.ams2.redhat.com [10.36.117.153]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DA66D215670D; Tue, 31 Jul 2018 12:59:07 +0000 (UTC) Subject: Re: [PATCH] x86: kvm: Restrict X86_FEATURE_VMMCALL to x86_64 platform To: whiteheadm@acm.org Cc: Linux Kernel Mailing List References: <20180730194059.5781-1-tedheadster@gmail.com> <7c274466-6d93-d1ba-8721-4d69f847b40f@redhat.com> From: Paolo Bonzini Openpgp: preference=signencrypt Autocrypt: addr=pbonzini@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Tue, 31 Jul 2018 12:59:08 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Tue, 31 Jul 2018 12:59:08 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'pbonzini@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 31/07/2018 14:57, tedheadster wrote: >> >> This shouldn't be necessary; for systems that don't have virtualization >> extensions, the comment explains why setting X86_FEATURE_VMMCALL is safe. >> >> But it is also wrong, because you can run a 32-bit kernel as a guest on >> a 64-bit processor, and then it should set X86_FEATURE_VMMCALL because >> the processor has the vmmcall instruction and not Intel's vmcall. >> > > Paolo, > I'm running this on a bare metal machine (no virtualization) with a > 32-bit AMD i486 class cpu. Should the feature be showing up in > /proc/cpuinfo under the 'flags' line? It does on my machine, and it > looked wrong to me. It's a bit silly, but it's not particularly wrong. Paolo