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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 AD22DECDE44 for ; Wed, 31 Oct 2018 21:30:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 66C4D2054F for ; Wed, 31 Oct 2018 21:30:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 66C4D2054F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726237AbeKAGa2 (ORCPT ); Thu, 1 Nov 2018 02:30:28 -0400 Received: from mga04.intel.com ([192.55.52.120]:41562 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725901AbeKAGa1 (ORCPT ); Thu, 1 Nov 2018 02:30:27 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 31 Oct 2018 14:30:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,449,1534834800"; d="scan'208";a="277316362" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.193]) by fmsmga006.fm.intel.com with ESMTP; 31 Oct 2018 14:30:36 -0700 Date: Wed, 31 Oct 2018 14:30:36 -0700 From: Sean Christopherson To: Dave Hansen Cc: Jethro Beekman , Jarkko Sakkinen , Andy Lutomirski , Andrew Lutomirski , X86 ML , Platform Driver , "nhorman@redhat.com" , "npmccallum@redhat.com" , "Ayoun, Serge" , "shay.katz-zamir@intel.com" , "linux-sgx@vger.kernel.org" , Andy Shevchenko , Dave Hansen , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , LKML Subject: Re: [PATCH v14 09/19] x86/mm: x86/sgx: Signal SEGV_SGXERR for #PFs w/ PF_SGX Message-ID: <20181031213036.GA23089@linux.intel.com> References: <20180926173516.GA10920@linux.intel.com> <2D60780F-ADB4-48A4-AB74-15683493D369@amacapital.net> <9835e288-ba98-2f9e-ac73-504db9512bb9@intel.com> <20180926204400.GA11446@linux.intel.com> <992b1d6d-cc0f-776f-d938-2a1f7cad52c8@intel.com> <20180927135603.GF8242@linux.intel.com> <2e7b81e1-818f-7d76-e2b4-793d9ec5d5a6@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2e7b81e1-818f-7d76-e2b4-793d9ec5d5a6@intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 01, 2018 at 03:03:30PM -0700, Dave Hansen wrote: > On 10/01/2018 02:42 PM, Jethro Beekman wrote: > > > > 1) Even though the vDSO function exists, userspace may still call > > `ENCLU[EENTER]` manually, so the fault handling as described in the > > current patch should also be maintained. > > Why? Circling back to this question, what if we take the easy way out and simply signal SIGSEGV without an SGX-specific code? I.e. treat #PF with X86_PF_SGX as an access error, no more no less. That should be sufficient for userspace to function, albeit with a little more effort, but presumably no more than would be needed to run on SGX1 hardware. AFAIK there isn't a way to prevent userspace from manually invoking EENTER, short of doing some really nasty text poking or PTE swizzling. We could declare using EENTER as unsupported, but that seems like cutting off the nose to spite the face. Supporting userspace EENTER in a limited capacity would allow people to do whatever crazy tricks they're wont to do without having to deal with absurd requests for the vDSO interface. If we go this route we could also add the vDSO stuff after basic SGX support is in mainline, obviously with approval from the powers that be.