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 53DA4C433B4 for ; Sat, 3 Apr 2021 16:26:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 185156124C for ; Sat, 3 Apr 2021 16:26:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236890AbhDCQ03 (ORCPT ); Sat, 3 Apr 2021 12:26:29 -0400 Received: from mga07.intel.com ([134.134.136.100]:39462 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236885AbhDCQ02 (ORCPT ); Sat, 3 Apr 2021 12:26:28 -0400 IronPort-SDR: HrUCufS7oBtfjsoE3obBG7a/pZf0/0cdfzAq68zGgZ6DqzSjMJjw/O1wyTgZk9tSJf2jQWUUTH ebbqqzVwUcEw== X-IronPort-AV: E=McAfee;i="6000,8403,9943"; a="256601153" X-IronPort-AV: E=Sophos;i="5.81,302,1610438400"; d="scan'208";a="256601153" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Apr 2021 09:26:24 -0700 IronPort-SDR: jZLPKI9jSdPjsSzI6dPmkjY/QHStUgkFSzNeHjVO2qysvR4/JcwQ5NWAmZiF2rl61NbBOEukJ1 x0e7grrAbolA== X-IronPort-AV: E=Sophos;i="5.81,302,1610438400"; d="scan'208";a="420089031" Received: from mwbraun-mobl.amr.corp.intel.com (HELO [10.251.5.155]) ([10.251.5.155]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Apr 2021 09:26:24 -0700 Subject: Re: [RFC v1 00/26] Add TDX Guest Support To: Andi Kleen Cc: Kuppuswamy Sathyanarayanan , Peter Zijlstra , Andy Lutomirski , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , Sean Christopherson , linux-kernel@vger.kernel.org References: <95e97456-478b-c6a2-f851-3b19ce794262@intel.com> <20210402024852.GK1285835@tassilo.jf.intel.com> <9bfa74a5-6a56-a2e0-7432-d35766099d54@intel.com> <20210402213219.GM1285835@tassilo.jf.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: <20210402213219.GM1285835@tassilo.jf.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 4/2/21 2:32 PM, Andi Kleen wrote: >> If we go this route, what are the rules and restrictions? Do we have to >> say "no MMIO in #VE"? > > All we have to say is "No MMIO in #VE before getting thd TDVEINFO arguments" > After that it can nest without problems. Well, not exactly. You still can't do things that will could cause a n unbounded recusive #VE. It doesn't seem *that* far fetched to think that someone might try to defer some work or dump data to the console. > If you nest before that the TDX will cause a triple fault. > > The code that cannot do it is a few lines in the early handler which > runs with interrupts off. >> Which brings up another related point: How do you debug TD guests? Does >> earlyprintk work? > > Today it works actually because serial ports are allowed. But I expect it to > be closed eventually because serial code is a lot of code to audit. > But you can always disable the filtering with a command line option and > then it will always work for debugging. Do we need a TDX-specific earlyprintk? I would imagine it's pretty easy to implement.