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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 63F53C432BE for ; Wed, 4 Aug 2021 19:19:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4AC8A60F58 for ; Wed, 4 Aug 2021 19:19:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240718AbhHDTUF (ORCPT ); Wed, 4 Aug 2021 15:20:05 -0400 Received: from mga18.intel.com ([134.134.136.126]:32885 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239615AbhHDTT4 (ORCPT ); Wed, 4 Aug 2021 15:19:56 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10066"; a="201177560" X-IronPort-AV: E=Sophos;i="5.84,295,1620716400"; d="scan'208";a="201177560" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Aug 2021 12:19:43 -0700 X-IronPort-AV: E=Sophos;i="5.84,295,1620716400"; d="scan'208";a="467228427" Received: from mjkendri-mobl.amr.corp.intel.com (HELO skuppusw-desk1.amr.corp.intel.com) ([10.254.17.117]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Aug 2021 12:19:42 -0700 From: Kuppuswamy Sathyanarayanan To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski Cc: Peter H Anvin , Dave Hansen , Tony Luck , Dan Williams , Andi Kleen , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 10/10] x86/tdx: Handle MWAIT and MONITOR Date: Wed, 4 Aug 2021 12:18:55 -0700 Message-Id: <20210804191855.2901927-11-sathyanarayanan.kuppuswamy@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210804191855.2901927-1-sathyanarayanan.kuppuswamy@linux.intel.com> References: <20210804191855.2901927-1-sathyanarayanan.kuppuswamy@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When running as a TDX guest, there are a number of existing, privileged instructions that do not work. If the guest kernel uses these instructions, the hardware generates a #VE. You can find the list of unsupported instructions in Intel Trust Domain Extensions (Intel® TDX) Module specification, sec 9.2.2 and in Guest-Host Communication Interface (GHCI) Specification for Intel TDX, sec 2.4.1. To prevent TD guests from using MWAIT/MONITOR instructions, the CPUID flags for these instructions are already disabled by the TDX module.      After the above mentioned preventive measures, if TD guests still execute these instructions, add appropriate warning message (WARN_ONCE()) in #VE handler. This handling behavior is same as KVM (which also treats MWAIT/MONITOR as nops with warning once in unsupported platforms). Signed-off-by: Kuppuswamy Sathyanarayanan Reviewed-by: Andi Kleen Reviewed-by: Dan Williams --- Changes since v3: * None Changes since v2: * None arch/x86/kernel/tdx.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index ab4f7c962ddd..4080f7546e62 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -360,6 +360,14 @@ int tdg_handle_virtualization_exception(struct pt_regs *regs, return -EFAULT; } break; + case EXIT_REASON_MONITOR_INSTRUCTION: + case EXIT_REASON_MWAIT_INSTRUCTION: + /* + * Something in the kernel used MONITOR or MWAIT despite + * X86_FEATURE_MWAIT being cleared for TDX guests. + */ + WARN_ONCE(1, "TD Guest used unsupported MWAIT/MONITOR instruction\n"); + break; default: pr_warn("Unexpected #VE: %lld\n", ve->exit_reason); return -EFAULT; -- 2.25.1