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 8F9C6C433ED for ; Wed, 31 Mar 2021 22:01:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 660B06109D for ; Wed, 31 Mar 2021 22:01:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232627AbhCaWBD (ORCPT ); Wed, 31 Mar 2021 18:01:03 -0400 Received: from mga11.intel.com ([192.55.52.93]:62506 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231676AbhCaWAf (ORCPT ); Wed, 31 Mar 2021 18:00:35 -0400 IronPort-SDR: A07JH/gQpo9UZi/hPkczR/r6R1Iyipm+1Is21weluBZ88C2lpQeQBA9dP1joPmQV+uLcxCnmwd elwLc8S3Aobw== X-IronPort-AV: E=McAfee;i="6000,8403,9940"; a="188840334" X-IronPort-AV: E=Sophos;i="5.81,295,1610438400"; d="scan'208";a="188840334" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Mar 2021 15:00:35 -0700 IronPort-SDR: wrdoTYr/42ISLP0b4O6OBy0ToBLByXBnlURGfNgKPd6KE/jnwCxCP8U18dqg74PnMjXpp6Zqtw VibEMx8FadLA== X-IronPort-AV: E=Sophos;i="5.81,295,1610438400"; d="scan'208";a="418873309" Received: from algolden-mobl1.amr.corp.intel.com (HELO [10.209.172.7]) ([10.209.172.7]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Mar 2021 15:00:34 -0700 Subject: Re: [PATCH v4 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD To: Sean Christopherson , Kuppuswamy Sathyanarayanan Cc: Peter Zijlstra , Andy Lutomirski , Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , linux-kernel@vger.kernel.org References: <2FE32855-EA5D-44E4-AACC-25E9B1476547@amacapital.net> 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: 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 3/31/21 2:53 PM, Sean Christopherson wrote: > On Wed, Mar 31, 2021, Kuppuswamy Sathyanarayanan wrote: >> Changes since v3: >> * WARN user if SEAM does not disable MONITOR/MWAIT instruction. > Why bother? There are a whole pile of features that are dictated by the TDX > module spec. MONITOR/MWAIT is about as uninteresting as it gets, e.g. absolute > worst case scenario is the guest kernel crashes, whereas a lot of spec violations > would compromise the security of the guest. So, what should we do? In the #VE handler: switch (exit_reason) { case SOMETHING_WE_HANDLE: blah(); break; ... default: pr_err("unhadled #VE, exit reason: %d\n", exit_reason); BUG_ON(1); } ? Is this the *ONLY* one of these, or are we going to have another twenty? If this is the only one, we might as well give a nice string error message. If there are twenty more, let's just dump the exit reason, BUG() and move on with our lives.