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 12215C47082 for ; Tue, 8 Jun 2021 22:17:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB4DE613AD for ; Tue, 8 Jun 2021 22:17:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234229AbhFHWTK (ORCPT ); Tue, 8 Jun 2021 18:19:10 -0400 Received: from mga03.intel.com ([134.134.136.65]:24422 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229548AbhFHWTJ (ORCPT ); Tue, 8 Jun 2021 18:19:09 -0400 IronPort-SDR: Z4yt8EIa/yFWa1cOhRaX1nTioOAufQsHsaug0B1ykujHuciE2AGvZFUyoG0nkrjfJ0eX6QjlRF vgCD6y+HTlcg== X-IronPort-AV: E=McAfee;i="6200,9189,10009"; a="204978864" X-IronPort-AV: E=Sophos;i="5.83,259,1616482800"; d="scan'208";a="204978864" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jun 2021 15:17:11 -0700 IronPort-SDR: X4kV1572j00CEByy05DM9UFMaTbGMkrQqVydBvzePj8j45d2fEWWZyfsyafVRaMDMRqiclE58u kH88GopTxC6A== X-IronPort-AV: E=Sophos;i="5.83,259,1616482800"; d="scan'208";a="637801595" Received: from ciball-mobl1.amr.corp.intel.com (HELO [10.252.140.48]) ([10.252.140.48]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jun 2021 15:17:10 -0700 Subject: Re: [RFC v2-fix-v3 1/1] x86/tdx: Skip WBINVD instruction for TDX guest To: Kuppuswamy Sathyanarayanan , Peter Zijlstra , Andy Lutomirski , Tony Luck , Dan Williams Cc: Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Raj Ashok , Sean Christopherson , linux-kernel@vger.kernel.org References: <20210608213527.739474-1-sathyanarayanan.kuppuswamy@linux.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210608213527.739474-1-sathyanarayanan.kuppuswamy@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/8/21 2:35 PM, Kuppuswamy Sathyanarayanan wrote: > Persistent memory is also currently not supported. Another code > path that uses WBINVD is the MTRR driver, but EPT/virtualization > always disables MTRRs so those are not needed. This all implies > WBINVD is not needed with current TDX. It's one thing to declare something unsupported. It's quite another to declare it unsupported and then back it up with code to ensure that any attempted use is thwarted. This patch certainly shows us half of the solution. But, to be complete, we also need to see the other half: where is the patch or documentation for why it is not *possible* to encounter persistent memory in a TDX guest? BTW, "persistent memory" is much more than Intel Optane DCPMM.