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 B1348C2B9F7 for ; Mon, 24 May 2021 23:43:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C6316140F for ; Mon, 24 May 2021 23:43:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230037AbhEXXo2 (ORCPT ); Mon, 24 May 2021 19:44:28 -0400 Received: from mga11.intel.com ([192.55.52.93]:47369 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230409AbhEXXnm (ORCPT ); Mon, 24 May 2021 19:43:42 -0400 IronPort-SDR: eo40VmN2Az43GYOqdog8Wvev3+TA96Bx2GejaijS16MPZMEPYzNprqdAYGoLyQCN+QPW9ZeVvp lZbInqTiNYSA== X-IronPort-AV: E=McAfee;i="6200,9189,9994"; a="199001896" X-IronPort-AV: E=Sophos;i="5.82,327,1613462400"; d="scan'208";a="199001896" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 May 2021 16:42:11 -0700 IronPort-SDR: b2QzJcpdMtdNQHjWqD3B0Xw4Ov8E9yoeGWxxM+39Kcs7BoZslPNs32NZZk3RfE9SYQqmiJQJIL 7CrliabdG+Hw== X-IronPort-AV: E=Sophos;i="5.82,327,1613462400"; d="scan'208";a="478844448" Received: from caknoll-mobl.amr.corp.intel.com (HELO [10.209.100.8]) ([10.209.100.8]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 May 2021 16:42:10 -0700 Subject: Re: [RFC v2-fix-v2 2/2] x86/tdx: Ignore WBINVD instruction for TDX guest To: Kuppuswamy Sathyanarayanan , Peter Zijlstra , Andy Lutomirski Cc: Tony Luck , Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , Sean Christopherson , linux-kernel@vger.kernel.org References: <37ad50ca-f568-4c62-56e2-9e9b1f34084c@linux.intel.com> <20210524233211.802033-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20210524233211.802033-2-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: <20210524233211.802033-2-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 5/24/21 4:32 PM, Kuppuswamy Sathyanarayanan wrote: > Functionally only DMA devices can notice a side effect from > WBINVD's cache flushing. This seems to be trying to make some kind of case that the only visible effects from WBINVD are for DMA devices. That's flat out wrong. It might be arguable that none of the other cases exist in a TDX guest, but it doesn't excuse making such a broad statement without qualification. Just grep in the kernel for a bunch of reasons this is wrong. Where did this come from?