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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 33BBCC3A5A1 for ; Fri, 23 Aug 2019 01:25:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0B4D3233A2 for ; Fri, 23 Aug 2019 01:25:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387995AbfHWBZV (ORCPT ); Thu, 22 Aug 2019 21:25:21 -0400 Received: from mga03.intel.com ([134.134.136.65]:24873 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726283AbfHWBZV (ORCPT ); Thu, 22 Aug 2019 21:25:21 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Aug 2019 18:25:19 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,419,1559545200"; d="scan'208";a="184069830" Received: from nmordaws-mobl1.amr.corp.intel.com (HELO localhost) ([10.252.38.129]) by orsmga006.jf.intel.com with ESMTP; 22 Aug 2019 18:25:17 -0700 Date: Fri, 23 Aug 2019 04:25:16 +0300 From: Jarkko Sakkinen To: Sean Christopherson Cc: linux-sgx@vger.kernel.org, Andy Lutomirski Subject: Re: [PATCH for_v22 v2 8/8] x86/sgx: Pass userspace source address directly to EADD Message-ID: <20190823012516.cogaoq63kceol37u@linux.intel.com> References: <20190813011252.4121-1-sean.j.christopherson@intel.com> <20190813011252.4121-9-sean.j.christopherson@intel.com> <74a9dbbed67ef131bf2179821ce74696120b35e1.camel@linux.intel.com> <20190822145049.GD25467@linux.intel.com> <5156a9c133e757dfcf8a8d003d39992aed6ade9a.camel@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5156a9c133e757dfcf8a8d003d39992aed6ade9a.camel@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: NeoMutt/20180716 Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Thu, Aug 22, 2019 at 08:00:15PM +0300, Jarkko Sakkinen wrote: > On Thu, 2019-08-22 at 07:50 -0700, Sean Christopherson wrote: > > On Thu, Aug 22, 2019 at 05:37:18PM +0300, Jarkko Sakkinen wrote: > > > On Mon, 2019-08-12 at 18:12 -0700, Sean Christopherson wrote: > > > > Invoke EADD with the userspace source address instead of first copying > > > > the data to a kernel page to avoid the overhead of alloc_page() and > > > > copy_from_user(). > > > > > > > > Suggested-by: Andy Lutomirski > > > > Signed-off-by: Sean Christopherson > > > > > > NAK because takes away TCS validation and the commit message > > > does not give any reasoning for doing that. > > > > Doh, I have a thorough explanation, but apparently it never made it from > > my head to the changelog. I'll send v2 as a standalone patch. > > Yeah, w/o explanation I won't just take away functionality :-) I came to realize that also from security perspective it might be helpful to EADD, not from a copy of the source, but from the actual source. So yes, I'm for not supporting copy approach at all. I think this viewpoint is important to note in addition to the performance perspective. /Jarkko