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,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 D4064C4363D for ; Tue, 6 Oct 2020 23:21:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 551B7206F4 for ; Tue, 6 Oct 2020 23:21:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726597AbgJFXVg (ORCPT ); Tue, 6 Oct 2020 19:21:36 -0400 Received: from mga03.intel.com ([134.134.136.65]:46817 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725947AbgJFXVg (ORCPT ); Tue, 6 Oct 2020 19:21:36 -0400 IronPort-SDR: clDxPIc3dThM9B4fq+AYHLLiPYkLLJrURjiZ56PRXxxKh0CLafq+cVpXrNrzqOovoFBNjff3aa 7VEEEtdn2NTA== X-IronPort-AV: E=McAfee;i="6000,8403,9766"; a="164809157" X-IronPort-AV: E=Sophos;i="5.77,344,1596524400"; d="scan'208";a="164809157" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Oct 2020 16:21:34 -0700 IronPort-SDR: VEl41zVVTvoYVJy06WsKjWx/blRN48fEKTknNoT7/m0qhcaNa0xc7faug+agI9D9PeJppJBa4e I3DiLWvspbNg== X-IronPort-AV: E=Sophos;i="5.77,344,1596524400"; d="scan'208";a="527659173" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.160]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Oct 2020 16:21:30 -0700 Date: Tue, 6 Oct 2020 16:21:29 -0700 From: Sean Christopherson To: Jarkko Sakkinen Cc: Jethro Beekman , x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Cedric Xing , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, bp@alien8.de, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com, mikko.ylinen@intel.com Subject: Re: [PATCH v39 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call Message-ID: <20201006232129.GB28981@linux.intel.com> References: <20201003045059.665934-1-jarkko.sakkinen@linux.intel.com> <20201003045059.665934-22-jarkko.sakkinen@linux.intel.com> <20201006025703.GG15803@linux.intel.com> <453c2d9b-0fd0-0d63-2bb9-096f255a6ff4@fortanix.com> <20201006151532.GA17610@linux.intel.com> <20201006172819.GA114208@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201006172819.GA114208@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Tue, Oct 06, 2020 at 08:28:19PM +0300, Jarkko Sakkinen wrote: > On Tue, Oct 06, 2020 at 08:15:32AM -0700, Sean Christopherson wrote: > > On Tue, Oct 06, 2020 at 10:30:16AM +0200, Jethro Beekman wrote: > > > On 2020-10-06 04:57, Sean Christopherson wrote: > > > > On Sat, Oct 03, 2020 at 07:50:56AM +0300, Jarkko Sakkinen wrote: > > > >> +struct sgx_enclave_run { > > > >> + __u64 tcs; > > > >> + __u64 user_handler; > > > >> + __u64 user_data; > > > >> + __u32 leaf; > > > > > > > > I am still very strongly opposed to omitting exit_reason. It is not at all > > > > difficult to imagine scenarios where 'leaf' alone is insufficient for the > > > > caller or its handler to deduce why the CPU exited the enclave. E.g. see > > > > Jethro's request for intercepting interrupts. > > > > > > Not entirely sure what this has to do with my request, I just expect to see > > > leaf=ERESUME in this case, I think? E.g. as you would see in EAX when calling > > > ENCLU. > > > > But how would you differentiate from the case that an exception occured in > > the enclave? That will also transfer control with leaf=ERESUME. If there > > was a prior exception and userspace didn't zero out the struct, there would > > be "valid" data in the exception fields. > > > > An exit_reason also would allow retrofitting the exception fields into a > > union, i.e. the fields are valid if and only if exit_reason is exception. > > Let's purge this a bit. Please remark where my logic goes wrong. I'm > just explaining how I've deduced the whole thing. > > The information was encoded in v38 version of the vDSO was exactly this: > > - On normal EEXIT, it got the value 0. > - Otherwise, it got the value 1. > > The leaf, then embdded to struct sgx_exception but essentially the same > field got the value from EAX, and the value that EAX had was only > written on exception path. > > Thus, I deduced that if you write $EEXIT to leaf on synchrous exit you > get the same information content, nothing gets overwritten. I.e. you > can make same conclusions as you would with those two struct fields. And then a third flavor comes along, e.g. Jethro's request interrupt case, and exit_reason can also return '2'. How do you handle that with only the leaf?