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 D42CFC47082 for ; Tue, 8 Jun 2021 17:53:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B9B5B61278 for ; Tue, 8 Jun 2021 17:53:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233976AbhFHRzm (ORCPT ); Tue, 8 Jun 2021 13:55:42 -0400 Received: from mga01.intel.com ([192.55.52.88]:27341 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233870AbhFHRzk (ORCPT ); Tue, 8 Jun 2021 13:55:40 -0400 IronPort-SDR: pkiVKGJ1uOTvevCU1Dla2Txec7JyI5BYcbSXW1orYteeqKpgdSrKz5X1mEj5auytdRavoQFotB 54G4akolHiVw== X-IronPort-AV: E=McAfee;i="6200,9189,10009"; a="226253591" X-IronPort-AV: E=Sophos;i="5.83,258,1616482800"; d="scan'208";a="226253591" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jun 2021 10:53:47 -0700 IronPort-SDR: mVyXRWAFrZrf+GpBCi3mRgr+6P4Ol+zuGZYKbCM8nM2Sr2ARLOygNXTDldNF+sDWMR+JWgmfBD u+2XzNzfY8Lw== X-IronPort-AV: E=Sophos;i="5.83,258,1616482800"; d="scan'208";a="637719012" 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 10:53:46 -0700 Subject: Re: [RFC v2 08/32] x86/traps: Add #VE support for TDX guest To: Sean Christopherson Cc: Kuppuswamy Sathyanarayanan , Peter Zijlstra , Andy Lutomirski , Dan Williams , Tony Luck , Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Raj Ashok , linux-kernel@vger.kernel.org References: <8a1d6930f784cb57c957cf20cea870947db91e05.1619458733.git.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 10:48 AM, Sean Christopherson wrote: > On Tue, Jun 08, 2021, Dave Hansen wrote: >> On 4/26/21 11:01 AM, Kuppuswamy Sathyanarayanan wrote: >>> +#ifdef CONFIG_INTEL_TDX_GUEST >>> +DEFINE_IDTENTRY(exc_virtualization_exception) >>> +{ >>> + struct ve_info ve; >>> + int ret; >>> + >>> + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); >>> + >>> + /* >>> + * Consume #VE info before re-enabling interrupts. It will be >>> + * re-enabled after executing the TDGETVEINFO TDCALL. >>> + */ >>> + ret = tdg_get_ve_info(&ve); >> Is it safe to have *anything* before the tdg_get_ve_info()? For >> instance, say that RCU_LOCKDEP_WARN() triggers. Will anything in there >> do MMIO? > I doubt it's safe, anything that's doing printing has the potential to trigger > #VE. Even if we can prove it's safe for all possible paths, I can't think of a > reason to allow anything that's not absolutely necessary before retrieving the > #VE info. What about tracing? Can I plop a kprobe in here or turn on ftrace?