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=-5.4 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 59607C4338F for ; Wed, 4 Aug 2021 21:48:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3B38561073 for ; Wed, 4 Aug 2021 21:48:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234765AbhHDVsz (ORCPT ); Wed, 4 Aug 2021 17:48:55 -0400 Received: from mga18.intel.com ([134.134.136.126]:45893 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234653AbhHDVsx (ORCPT ); Wed, 4 Aug 2021 17:48:53 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10066"; a="201204390" X-IronPort-AV: E=Sophos;i="5.84,295,1620716400"; d="scan'208";a="201204390" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Aug 2021 14:48:40 -0700 X-IronPort-AV: E=Sophos;i="5.84,295,1620716400"; d="scan'208";a="671115571" Received: from cmalmber-mobl1.amr.corp.intel.com (HELO [10.212.219.120]) ([10.212.219.120]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Aug 2021 14:48:39 -0700 Subject: Re: [PATCH v5 11/12] x86/tdx: Don't write CSTAR MSR on Intel To: "Kuppuswamy, Sathyanarayanan" , Sean Christopherson Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , Peter H Anvin , Tony Luck , Dan Williams , Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , x86@kernel.org, linux-kernel@vger.kernel.org References: <20210804181329.2899708-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20210804181329.2899708-12-sathyanarayanan.kuppuswamy@linux.intel.com> <4c1ee7b9-9941-fdc4-73f5-3d2ef0530556@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: <4c1ee7b9-9941-fdc4-73f5-3d2ef0530556@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 8/4/21 2:03 PM, Kuppuswamy, Sathyanarayanan wrote: >> Is #GP the actual TDX-Module behavior?  If so, isn't that a >> contradiction with > > No, #GP is triggered by guest. ... >> Regardless of #GP versus #VE, "Table 16.2 MSR Virtualization" needs >> to state the actual behavior. > > Even in this case, it will trigger #VE. But since CSTAR MSR is not > supported, write to it will fail and leads to #VE fault. Sathya, I think there might be a mixup of terminology here that's confusing. I'm confused by this exchange. In general, we refer to hardware exceptions by their architecture names: #GP for general protection fault, #PF for page fault, #VE for Virtualization Exception. Those hardware exceptions are wired up to software handlers: #GP lands in asm_exc_general_protection #PF ends up in exc_page_fault #VE ends up in exc_virtualization_exception ... and more of course But, to add to the confusion, the #VE handler (exc_virtualization_exception()) itself calls (or did once upon a time call) do_general_protection() when it can't handle something. do_general_protection() is (was?) *ALSO* called by the #GP handler. So, is that what you meant? By "#GP is triggered by guest", you mean that a write to the CSTAR MSR and the resulting #VE will end up being handled in a way that is similar to how a #GP hardware exception would have been handled? If that's what you meant, I'm not _sure_ that's totally accurate. Could you elaborate on this a bit? It also would be really handy if you were able to adopt the terminology I talked about above. It will really make things less confusing.