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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 B5E5AC433ED for ; Thu, 1 Apr 2021 22:25:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F17E610A5 for ; Thu, 1 Apr 2021 22:25:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234634AbhDAWZZ (ORCPT ); Thu, 1 Apr 2021 18:25:25 -0400 Received: from mga09.intel.com ([134.134.136.24]:15743 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233789AbhDAWZY (ORCPT ); Thu, 1 Apr 2021 18:25:24 -0400 IronPort-SDR: DiuTLWy5ks/iutoT3DkEKk/wwWWukTz5/IDHb70ZswwrhjuBB22NmbEzqnX/zFGPv8FQ+Zs88f OoVj3rVdzK4Q== X-IronPort-AV: E=McAfee;i="6000,8403,9941"; a="192446191" X-IronPort-AV: E=Sophos;i="5.81,296,1610438400"; d="scan'208";a="192446191" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2021 15:25:24 -0700 IronPort-SDR: H7wg1ZKmAqZo2RE31j8BZztOdcTcVFJ9QTcXyjzYgyev32YuHTWndqIo1usOEM36PbC3U1lZMo h+NSZdNDlS5Q== X-IronPort-AV: E=Sophos;i="5.81,296,1610438400"; d="scan'208";a="419389337" Received: from maorache-mobl.amr.corp.intel.com (HELO skuppusw-mobl5.amr.corp.intel.com) ([10.213.170.140]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2021 15:25:23 -0700 Subject: Re: [RFC v1 03/26] x86/cpufeatures: Add is_tdx_guest() interface To: Dave Hansen , Peter Zijlstra , Andy Lutomirski Cc: Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , Sean Christopherson , linux-kernel@vger.kernel.org, Sean Christopherson References: <83c8fcff9ac09f73924104cfb534258747e98bff.1612563142.git.sathyanarayanan.kuppuswamy@linux.intel.com> <0116481d-581b-9433-3641-47e39550b99a@intel.com> <8f0bd4e5-195b-7e65-f780-f5e31d72cfe8@linux.intel.com> <3aee61d5-9cc2-2c3c-00ea-f3ec7d5f7e04@intel.com> From: "Kuppuswamy, Sathyanarayanan" Message-ID: Date: Thu, 1 Apr 2021 15:25:20 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <3aee61d5-9cc2-2c3c-00ea-f3ec7d5f7e04@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/1/21 2:19 PM, Dave Hansen wrote: > On 4/1/21 2:15 PM, Kuppuswamy, Sathyanarayanan wrote: >> On 4/1/21 2:08 PM, Dave Hansen wrote: >>> On 2/5/21 3:38 PM, Kuppuswamy Sathyanarayanan wrote: >>>> +bool is_tdx_guest(void) >>>> +{ >>>> +    return static_cpu_has(X86_FEATURE_TDX_GUEST); >>>> +} >>> >>> Why do you need is_tdx_guest() as opposed to calling >>> cpu_feature_enabled(X86_FEATURE_TDX_GUEST) everywhere? >> >> is_tdx_guest() is also implemented/used in compressed >> code (which uses native_cpuid calls). I don't think >> we can use cpu_feature_enabled(X86_FEATURE_TDX_GUEST) in >> compressed code right? Also is_tdx_guest() looks easy >> to read and use. > > OK, but how many of the is_tdx_guest() uses are in the compressed code? > Why has its use spread beyond that? Its only used in handling in/out instructions in compressed code. But this code shared with in/out handling on non-compressed code. #define __out(bwl, bw) \ do { \ if (is_tdx_guest()) { \ asm volatile("call tdg_out" #bwl : : \ "a"(value), "d"(port)); \ } else { \ asm volatile("out" #bwl " %" #bw "0, %w1" : : \ "a"(value), "Nd"(port)); \ } \ } while (0) #define __in(bwl, bw) \ do { \ if (is_tdx_guest()) { \ asm volatile("call tdg_in" #bwl : \ "=a"(value) : "d"(port)); \ } else { \ asm volatile("in" #bwl " %w1, %" #bw "0" : \ "=a"(value) : "Nd"(port)); \ } \ } while (0) > -- Sathyanarayanan Kuppuswamy Linux Kernel Developer