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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 9D910C6786F for ; Thu, 1 Nov 2018 17:44:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7543020657 for ; Thu, 1 Nov 2018 17:44:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7543020657 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.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 S1728036AbeKBCsg (ORCPT ); Thu, 1 Nov 2018 22:48:36 -0400 Received: from mga06.intel.com ([134.134.136.31]:17010 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726085AbeKBCsg (ORCPT ); Thu, 1 Nov 2018 22:48:36 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 01 Nov 2018 10:44:38 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,452,1534834800"; d="scan'208";a="92997714" Received: from btyborox-mobl.ger.corp.intel.com ([10.249.254.138]) by FMSMGA003.fm.intel.com with ESMTP; 01 Nov 2018 10:44:29 -0700 Date: Thu, 1 Nov 2018 19:44:27 +0200 (EET) From: Jarkko Sakkinen X-X-Sender: jsakkine@jsakkine-mobl1 To: Jarkko Sakkinen cc: Sean Christopherson , Dave Hansen , Jethro Beekman , 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 In-Reply-To: Message-ID: 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> <20181031213036.GA23089@linux.intel.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 1 Nov 2018, Jarkko Sakkinen wrote: > On Wed, 31 Oct 2018, Sean Christopherson wrote: >> 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. >> > > Yeah, this would give stable behavior when vDSO functions are not > available. > > Here's a question: if we implement this behavior, could be upstream > series without vDSO's first and after those changes have been landed > we would continue with the vDSO's? Right, it was in your last paragraph, sorry. Yeah, I fully support this idea. It will be easier also to work on the vDSO's once we have something landed (instead of working on a moving platform). /Jarkko