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 98321C43219 for ; Mon, 29 Apr 2019 09:54:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 70AB6214AF for ; Mon, 29 Apr 2019 09:54:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727788AbfD2Jyx (ORCPT ); Mon, 29 Apr 2019 05:54:53 -0400 Received: from mga03.intel.com ([134.134.136.65]:42225 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727624AbfD2Jyx (ORCPT ); Mon, 29 Apr 2019 05:54:53 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Apr 2019 02:54:52 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,409,1549958400"; d="scan'208";a="146730353" Received: from genxtest-ykzhao.sh.intel.com (HELO [10.239.143.71]) ([10.239.143.71]) by fmsmga007.fm.intel.com with ESMTP; 29 Apr 2019 02:54:51 -0700 Subject: Re: [RFC PATCH v5 4/4] x86/acrn: Add hypercall for ACRN guest To: Borislav Petkov Cc: Ingo Molnar , "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "tglx@linutronix.de" , "Chen, Jason CJ" References: <1556067260-9128-1-git-send-email-yakui.zhao@intel.com> <1556067260-9128-5-git-send-email-yakui.zhao@intel.com> <20190425070712.GA57256@gmail.com> <6dd021a9-e2c0-ee84-55fd-3e6dfb4bd944@intel.com> <20190425110025.GA16164@zn.tnic> <473d145c-4bfd-4ec8-34c3-8a26a78fe40d@intel.com> <20190427085816.GB12360@zn.tnic> <20190428100309.GA2334@zn.tnic> <4c5ca6d7-ffb1-a5a5-9e46-9057802318e0@intel.com> <20190429073625.GA2324@zn.tnic> From: "Zhao, Yakui" Message-ID: <923a3152-8029-14e9-9713-871b041c9c99@intel.com> Date: Mon, 29 Apr 2019 17:52:13 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20190429073625.GA2324@zn.tnic> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019年04月29日 15:36, Borislav Petkov wrote: > On Mon, Apr 29, 2019 at 09:24:12AM +0800, Zhao, Yakui wrote: >> Yes. "movq" only indicates explicitly that it is 64-bit mov as ACRN guest >> only works under 64-bit mode. >> I also check the usage of "mov" and "movq" in this scenario. There is no >> difference except that the movq is an explicit 64-op. > > Damn, I'm tired of explaining this: it is explicit only to the code > reader. gcc generates the *same* instruction no matter whether it has a > "q" suffix or not as long as the destination register is a 64-bit one. > > If you prefer to have it explicit, sure, use "movq". Hi, Borislav Thanks for the detailed explanation. "movq" will be used so that it is explicit to the code reader although the same binary is generated for "movq" and "mov" in this scenario. And thank you again for giving a lot of helps about removing the usage of explicit register variable. Best regards Yakui >