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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 AEABBC47257 for ; Wed, 6 May 2020 22:14:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88D3B20753 for ; Wed, 6 May 2020 22:14:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729980AbgEFWOY (ORCPT ); Wed, 6 May 2020 18:14:24 -0400 Received: from mga02.intel.com ([134.134.136.20]:5914 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729907AbgEFWOY (ORCPT ); Wed, 6 May 2020 18:14:24 -0400 IronPort-SDR: MqlXIOF+p6TBh/uiJTNVxso8C9alj+KzpJynjm2p7heVK3cEy9NT6DtBigF4sAOYz+Ft9DWZSW FTOJhVySdNnw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 May 2020 15:14:23 -0700 IronPort-SDR: Uneb1M7Psi3ugumKhUNct7/f26jE2pWT5+4AbHUaJmznhT/LdWVnTzyBAxCk0K46oz1mbrEcmn 1vP8utLkNd9Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,360,1583222400"; d="scan'208";a="369930304" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.152]) by fmsmga001.fm.intel.com with ESMTP; 06 May 2020 15:14:22 -0700 Date: Wed, 6 May 2020 15:14:22 -0700 From: Sean Christopherson To: Nathaniel McCallum Cc: Jarkko Sakkinen , linux-kernel@vger.kernel.org, x86@kernel.org, linux-sgx@vger.kernel.org, akpm@linux-foundation.org, dave.hansen@intel.com, Neil Horman , "Huang, Haitao" , andriy.shevchenko@linux.intel.com, tglx@linutronix.de, "Svahn, Kai" , bp@alien8.de, Josh Triplett , luto@kernel.org, kai.huang@intel.com, David Rientjes , "Xing, Cedric" , Patrick Uiterwijk Subject: Re: [PATCH v29 00/20] Intel SGX foundations Message-ID: <20200506221422.GK3329@linux.intel.com> References: <20200421215316.56503-1-jarkko.sakkinen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Wed, May 06, 2020 at 05:42:42PM -0400, Nathaniel McCallum wrote: > Tested on Enarx. This requires a patch[0] for v29 support. > > Tested-by: Nathaniel McCallum > > However, we did uncover a small usability issue. See below. > > [0]: https://github.com/enarx/enarx/pull/507/commits/80da2352aba46aa7bc6b4d1fccf20fe1bda58662 ... > > * Disallow mmap(PROT_NONE) from /dev/sgx. Any mapping (e.g. anonymous) can > > be used to reserve the address range. Now /dev/sgx supports only opaque > > mappings to the (initialized) enclave data. > > The statement "Any mapping..." isn't actually true. > > Enarx creates a large enclave (currently 64GiB). This worked when we > created a file-backed mapping on /dev/sgx/enclave. However, switching > to an anonymous mapping fails with ENOMEM. We suspect this is because > the kernel attempts to allocate all the pages and zero them but there > is insufficient RAM available. We currently work around this by > creating a shared mapping on /dev/zero. Hmm, the kernel shouldn't actually allocate physical pages unless they're written. I'll see if I can reproduce. > If we want to keep this mmap() strategy, we probably don't want to > advise mmap(ANON) if it allocates all the memory for the enclave ahead > of time, even if it won't be used. This would be wasteful. > > OTOH, having to mmap("/dev/zero") seems a bit awkward.