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 A2088C47082 for ; Tue, 8 Jun 2021 22:53:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7477B6128A for ; Tue, 8 Jun 2021 22:53:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234668AbhFHWzT (ORCPT ); Tue, 8 Jun 2021 18:55:19 -0400 Received: from mga07.intel.com ([134.134.136.100]:3029 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229548AbhFHWzR (ORCPT ); Tue, 8 Jun 2021 18:55:17 -0400 IronPort-SDR: 3QAdO1vLlFP4NPxce18oXmulctWcNBMWS7ZO5HjpPu3iVbVvyHCCvJWNyZ1K5A9tvVYz79Er3a JfK0vxUo+xnQ== X-IronPort-AV: E=McAfee;i="6200,9189,10009"; a="268816258" X-IronPort-AV: E=Sophos;i="5.83,259,1616482800"; d="scan'208";a="268816258" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jun 2021 15:53:22 -0700 IronPort-SDR: 5V9L+xxkNBtnpRNXWOkneUv3t/8dyNYPKx5Rj4ioNf2W4PCYuXoJgtdR26T1eso1PM091XUSvO gYuhT+XSW54A== X-IronPort-AV: E=Sophos;i="5.83,259,1616482800"; d="scan'208";a="637812732" 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 15:53:19 -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: 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 3:36 PM, Kuppuswamy, Sathyanarayanan wrote: > On 6/8/21 3:17 PM, Dave Hansen wrote: >> 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. > > Only audited and supported drivers will be allowed to enumerate after > device filter support patch is merged. Till we merge that patch, If > any of these unsupported features (with WBINVD usage) are enabled in TDX, > it will lead to sigfault (due to unhandled #VE). A kernel driver using WBINVD will "sigfault"? I'm not sure what that means. How does the kernel "sigfault"? > In this patch we only create exception for ACPI sleep driver code. If > commit log is confusing, I can remove information about other unsupported > feature (with WBINVD usage). Yes, the changelog is horribly confusing. But simply removing this information is insufficient to rectify the deficiency. I've lost trust that due diligence will be performed on this series on its own. I've seen too many broken promises and too many holes. Here's what I want to see: a list of all of the unique call sites for WBINVD in the kernel. I want a written down methodology for how the list of call sites was generated. I want to see an item-by-item list of why those call sites are unreachable with the TDX guest code. It might be because they've been patched in this patch, or the driver has been disabled, or because the TDX architecture spec would somehow prohibit the situation where it might be needed. But, there needs to be a list, and you have to show your work. If you refer to code from this series as helping to prevent WBINVD, then it has to be earlier in this series, not in some other series and not later in this series. Just eyeballing it, there are ~50 places in the kernel that need auditing. Right now, we mostly have indiscriminate hand-waving about this not being a problem. It's a hard NAK from me on this patch until this audit is in place.