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 D19A4C48BCD for ; Wed, 9 Jun 2021 23:55:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A8FD7613F0 for ; Wed, 9 Jun 2021 23:55:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229943AbhFIX5x (ORCPT ); Wed, 9 Jun 2021 19:57:53 -0400 Received: from mga14.intel.com ([192.55.52.115]:56072 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229507AbhFIX5v (ORCPT ); Wed, 9 Jun 2021 19:57:51 -0400 IronPort-SDR: HKfR415D+KUWlt1KJ1R57gTwZjrHbHVmZ8R8KbCbWm9HZ7sr4GKeqdAuvbW+xbBnMwTxjh39yy Qk5RBjUsZR5w== X-IronPort-AV: E=McAfee;i="6200,9189,10010"; a="205008169" X-IronPort-AV: E=Sophos;i="5.83,262,1616482800"; d="scan'208";a="205008169" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Jun 2021 16:55:56 -0700 IronPort-SDR: JfAqpoIF5W03HnE3VjhOzj3tnrKC0kP0bXfU4buYWuoDX6a7HPat1hu+Ilgi6vYgrYADwW7/UY ceePn2A5vO0w== X-IronPort-AV: E=Sophos;i="5.83,262,1616482800"; d="scan'208";a="482591226" Received: from dspaldin-mobl.amr.corp.intel.com (HELO [10.212.158.45]) ([10.212.158.45]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Jun 2021 16:55:42 -0700 Subject: Re: [RFC v2-fix-v5 1/1] x86: Skip WBINVD instruction for VM guest To: "Kuppuswamy, Sathyanarayanan" , Dan Williams Cc: Peter Zijlstra , Andy Lutomirski , Tony Luck , Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Raj Ashok , Sean Christopherson , Linux Kernel Mailing List References: <973add45-9fd2-7abc-3a97-96a26c263ea0@linux.intel.com> <20210609194926.1949859-1-sathyanarayanan.kuppuswamy@linux.intel.com> <7c06b567-9a65-8c7c-6046-3dcb32d4bb15@intel.com> <2184400d-856e-ed4c-b23d-77b7dfd72658@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: <2184400d-856e-ed4c-b23d-77b7dfd72658@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 6/9/21 2:42 PM, Kuppuswamy, Sathyanarayanan wrote: > On 6/9/21 2:38 PM, Dan Williams wrote: >>> In TDX guests, these WBINVD operations cause #VE exceptions.  For debug, >>> it would be ideal for the #VE handler to be able to WARN() when an >>> unexpected WBINVD occurs. (<--- problem #2) >> ...but it doesn't WARN() it triggers unhandled #VE, unless I missed >> another patch that precedes this that turns it into a WARN()? If a >> code path expects WBINVD for correct operation and the guest can't >> execute that sounds fatal, not a WARN to me. > > Yes. It is not WARN. It is a fatal unhandled exception. That makes the problem statement a wee bit different, but it should still be pretty easy to explain: In TDX guests, these WBINVD operations cause #VE exceptions. While some #VE exceptions can be handled, there is no recourse for a TDX guest to handle a WBINVD and it will panic(). (<--- problem #2)