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,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 3227BC2B9F8 for ; Mon, 24 May 2021 23:32:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 040AB6140B for ; Mon, 24 May 2021 23:32:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229643AbhEXXd6 (ORCPT ); Mon, 24 May 2021 19:33:58 -0400 Received: from mga09.intel.com ([134.134.136.24]:39314 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229539AbhEXXdx (ORCPT ); Mon, 24 May 2021 19:33:53 -0400 IronPort-SDR: PywwgtOaZtIt5Mm593VgHVvpNpLvuqHA08g9bT+xskBIn+qN46PTcixCZbB4S9BCYNzUxKQfsG LLjpIJ5ub3Vw== X-IronPort-AV: E=McAfee;i="6200,9189,9994"; a="202074821" X-IronPort-AV: E=Sophos;i="5.82,327,1613462400"; d="scan'208";a="202074821" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 May 2021 16:32:23 -0700 IronPort-SDR: 7uMNqZ775dr+DK5pjuHABDlJJ0Ul037vTPBqrt9w2+zwa54c8TRZ3iufdyjGAWJkzKNHsahpw9 blS0xPtmnteA== X-IronPort-AV: E=Sophos;i="5.82,327,1613462400"; d="scan'208";a="476126860" Received: from eyoukerh-mobl.ger.corp.intel.com (HELO skuppusw-desk1.amr.corp.intel.com) ([10.254.2.69]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 May 2021 16:32:22 -0700 From: Kuppuswamy Sathyanarayanan To: Peter Zijlstra , Andy Lutomirski , Dave Hansen Cc: Tony Luck , Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , Sean Christopherson , Kuppuswamy Sathyanarayanan , linux-kernel@vger.kernel.org Subject: [RFC v2-fix-v2 1/2] x86/tdx: Handle MWAIT and MONITOR Date: Mon, 24 May 2021 16:32:10 -0700 Message-Id: <20210524233211.802033-1-sathyanarayanan.kuppuswamy@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <37ad50ca-f568-4c62-56e2-9e9b1f34084c@linux.intel.com> References: <37ad50ca-f568-4c62-56e2-9e9b1f34084c@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 --- Changes since RFC v2: * Moved WBINVD related changes to a new patch. * Fixed commit log as per review comments. 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 3e961fdfdae0..3800c7cbace3 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -511,6 +511,14 @@ int tdg_handle_virtualization_exception(struct pt_regs *regs, case EXIT_REASON_EPT_VIOLATION: ve->instr_len = tdg_handle_mmio(regs, ve); 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