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 68A48ECE561 for ; Fri, 14 Sep 2018 21:33:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1EBD02083A for ; Fri, 14 Sep 2018 21:33:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1EBD02083A 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 S1728264AbeIOCt5 (ORCPT ); Fri, 14 Sep 2018 22:49:57 -0400 Received: from mga07.intel.com ([134.134.136.100]:3354 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726969AbeIOCt5 (ORCPT ); Fri, 14 Sep 2018 22:49:57 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Sep 2018 14:33:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,374,1531810800"; d="scan'208";a="91843101" Received: from ray.jf.intel.com (HELO [10.7.198.166]) ([10.7.198.166]) by orsmga002.jf.intel.com with ESMTP; 14 Sep 2018 14:33:37 -0700 Subject: Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW To: Yu-cheng Yu , Peter Zijlstra References: <1535660494.28258.36.camel@intel.com> <1535662366.28781.6.camel@intel.com> <20180831095300.GF24124@hirez.programming.kicks-ass.net> <1535726032.32537.0.camel@intel.com> <1535730524.501.13.camel@intel.com> <6d31bd30-6d5b-bbde-1e97-1d8255eff76d@linux.intel.com> <20180831162920.GQ24124@hirez.programming.kicks-ass.net> <1536957543.12990.9.camel@intel.com> <8d9ce0e9-8fc7-8c68-4aa9-9aed9ee949f2@linux.intel.com> <1536959337.12990.27.camel@intel.com> Cc: Jann Horn , the arch/x86 maintainers , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Florian Weimer , hjl.tools@gmail.com, Jonathan Corbet , keescook@chromium.org, Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , ravi.v.shankar@intel.com, vedvyas.shanbhogue@intel.com From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@linux.intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzShEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gPGRhdmVAc3I3MS5uZXQ+wsF7BBMBAgAlAhsDBgsJCAcDAgYVCAIJ CgsEFgIDAQIeAQIXgAUCTo3k0QIZAQAKCRBoNZUwcMmSsMO2D/421Xg8pimb9mPzM5N7khT0 2MCnaGssU1T59YPE25kYdx2HntwdO0JA27Wn9xx5zYijOe6B21ufrvsyv42auCO85+oFJWfE K2R/IpLle09GDx5tcEmMAHX6KSxpHmGuJmUPibHVbfep2aCh9lKaDqQR07gXXWK5/yU1Dx0r VVFRaHTasp9fZ9AmY4K9/BSA3VkQ8v3OrxNty3OdsrmTTzO91YszpdbjjEFZK53zXy6tUD2d e1i0kBBS6NLAAsqEtneplz88T/v7MpLmpY30N9gQU3QyRC50jJ7LU9RazMjUQY1WohVsR56d ORqFxS8ChhyJs7BI34vQusYHDTp6PnZHUppb9WIzjeWlC7Jc8lSBDlEWodmqQQgp5+6AfhTD kDv1a+W5+ncq+Uo63WHRiCPuyt4di4/0zo28RVcjtzlGBZtmz2EIC3vUfmoZbO/Gn6EKbYAn rzz3iU/JWV8DwQ+sZSGu0HmvYMt6t5SmqWQo/hyHtA7uF5Wxtu1lCgolSQw4t49ZuOyOnQi5 f8R3nE7lpVCSF1TT+h8kMvFPv3VG7KunyjHr3sEptYxQs4VRxqeirSuyBv1TyxT+LdTm6j4a mulOWf+YtFRAgIYyyN5YOepDEBv4LUM8Tz98lZiNMlFyRMNrsLV6Pv6SxhrMxbT6TNVS5D+6 UorTLotDZKp5+M7BTQRUY85qARAAsgMW71BIXRgxjYNCYQ3Xs8k3TfAvQRbHccky50h99TUY sqdULbsb3KhmY29raw1bgmyM0a4DGS1YKN7qazCDsdQlxIJp9t2YYdBKXVRzPCCsfWe1dK/q 66UVhRPP8EGZ4CmFYuPTxqGY+dGRInxCeap/xzbKdvmPm01Iw3YFjAE4PQ4hTMr/H76KoDbD cq62U50oKC83ca/PRRh2QqEqACvIH4BR7jueAZSPEDnzwxvVgzyeuhwqHY05QRK/wsKuhq7s UuYtmN92Fasbxbw2tbVLZfoidklikvZAmotg0dwcFTjSRGEg0Gr3p/xBzJWNavFZZ95Rj7Et db0lCt0HDSY5q4GMR+SrFbH+jzUY/ZqfGdZCBqo0cdPPp58krVgtIGR+ja2Mkva6ah94/oQN lnCOw3udS+Eb/aRcM6detZr7XOngvxsWolBrhwTQFT9D2NH6ryAuvKd6yyAFt3/e7r+HHtkU kOy27D7IpjngqP+b4EumELI/NxPgIqT69PQmo9IZaI/oRaKorYnDaZrMXViqDrFdD37XELwQ gmLoSm2VfbOYY7fap/AhPOgOYOSqg3/Nxcapv71yoBzRRxOc4FxmZ65mn+q3rEM27yRztBW9 AnCKIc66T2i92HqXCw6AgoBJRjBkI3QnEkPgohQkZdAb8o9WGVKpfmZKbYBo4pEAEQEAAcLB XwQYAQIACQUCVGPOagIbDAAKCRBoNZUwcMmSsJeCEACCh7P/aaOLKWQxcnw47p4phIVR6pVL e4IEdR7Jf7ZL00s3vKSNT+nRqdl1ugJx9Ymsp8kXKMk9GSfmZpuMQB9c6io1qZc6nW/3TtvK pNGz7KPPtaDzvKA4S5tfrWPnDr7n15AU5vsIZvgMjU42gkbemkjJwP0B1RkifIK60yQqAAlT YZ14P0dIPdIPIlfEPiAWcg5BtLQU4Wg3cNQdpWrCJ1E3m/RIlXy/2Y3YOVVohfSy+4kvvYU3 lXUdPb04UPw4VWwjcVZPg7cgR7Izion61bGHqVqURgSALt2yvHl7cr68NYoFkzbNsGsye9ft M9ozM23JSgMkRylPSXTeh5JIK9pz2+etco3AfLCKtaRVysjvpysukmWMTrx8QnI5Nn5MOlJj 1Ov4/50JY9pXzgIDVSrgy6LYSMc4vKZ3QfCY7ipLRORyalFDF3j5AGCMRENJjHPD6O7bl3Xo 4DzMID+8eucbXxKiNEbs21IqBZbbKdY1GkcEGTE7AnkA3Y6YB7I/j9mQ3hCgm5muJuhM/2Fr OPsw5tV/LmQ5GXH0JQ/TZXWygyRFyyI2FqNTx4WHqUn3yFj8rwTAU1tluRUYyeLy0ayUlKBH ybj0N71vWO936MqP6haFERzuPAIpxj2ezwu0xb1GjTk4ynna6h5GjnKgdfOWoRtoWndMZxbA z5cecg== Message-ID: <9366d924-cd67-1d2d-b78d-809bb46e7186@linux.intel.com> Date: Fri, 14 Sep 2018 14:33:36 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1536959337.12990.27.camel@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/14/2018 02:08 PM, Yu-cheng Yu wrote: > On Fri, 2018-09-14 at 13:46 -0700, Dave Hansen wrote: >> On 09/14/2018 01:39 PM, Yu-cheng Yu wrote: >>> >>> With the updated ptep_set_wrprotect() below, I did MADV_WILLNEED to a shadow >>> stack of 8 MB, then 10,000 fork()'s, but could not prove it is more or less >>> efficient than the other.  So can we say this is probably fine in terms of >>> efficiency? BTW, I wasn't particularly concerned about shadow stacks. Plain old memory is affected by this change too. Right? >> Well, the first fork() will do all the hard work.  I don't think >> subsequent fork()s will be affected. > > Are you talking about a recent commit: > >     1b2de5d0 mm/cow: don't bother write protecting already write-protected pages > > With that, subsequent fork()s will not do all the hard work. > However, I have not done that for shadow stack PTEs (do we want to do that?). > I think the additional benefit for shadow stack is small? You're right. mprotect() doesn't use this path. But, that reminds me, can you take a quick look at change_pte_range() and double-check that it's not affected by this issue? From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW Date: Fri, 14 Sep 2018 14:33:36 -0700 Message-ID: <9366d924-cd67-1d2d-b78d-809bb46e7186@linux.intel.com> References: <1535660494.28258.36.camel@intel.com> <1535662366.28781.6.camel@intel.com> <20180831095300.GF24124@hirez.programming.kicks-ass.net> <1535726032.32537.0.camel@intel.com> <1535730524.501.13.camel@intel.com> <6d31bd30-6d5b-bbde-1e97-1d8255eff76d@linux.intel.com> <20180831162920.GQ24124@hirez.programming.kicks-ass.net> <1536957543.12990.9.camel@intel.com> <8d9ce0e9-8fc7-8c68-4aa9-9aed9ee949f2@linux.intel.com> <1536959337.12990.27.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <1536959337.12990.27.camel@intel.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Yu-cheng Yu , Peter Zijlstra Cc: Jann Horn , the arch/x86 maintainers , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Florian Weimer , hjl.tools@gmail.com, Jonathan Corbet , keescook@chromium.org, Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek List-Id: linux-api@vger.kernel.org On 09/14/2018 02:08 PM, Yu-cheng Yu wrote: > On Fri, 2018-09-14 at 13:46 -0700, Dave Hansen wrote: >> On 09/14/2018 01:39 PM, Yu-cheng Yu wrote: >>> >>> With the updated ptep_set_wrprotect() below, I did MADV_WILLNEED to a shadow >>> stack of 8 MB, then 10,000 fork()'s, but could not prove it is more or less >>> efficient than the other.  So can we say this is probably fine in terms of >>> efficiency? BTW, I wasn't particularly concerned about shadow stacks. Plain old memory is affected by this change too. Right? >> Well, the first fork() will do all the hard work.  I don't think >> subsequent fork()s will be affected. > > Are you talking about a recent commit: > >     1b2de5d0 mm/cow: don't bother write protecting already write-protected pages > > With that, subsequent fork()s will not do all the hard work. > However, I have not done that for shadow stack PTEs (do we want to do that?). > I think the additional benefit for shadow stack is small? You're right. mprotect() doesn't use this path. But, that reminds me, can you take a quick look at change_pte_range() and double-check that it's not affected by this issue? From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by kanga.kvack.org (Postfix) with ESMTP id E18BC8E0001 for ; Fri, 14 Sep 2018 17:33:38 -0400 (EDT) Received: by mail-pf1-f199.google.com with SMTP id z18-v6so5214079pfe.19 for ; Fri, 14 Sep 2018 14:33:38 -0700 (PDT) Received: from mga06.intel.com (mga06.intel.com. [134.134.136.31]) by mx.google.com with ESMTPS id j37-v6si8473840pgl.432.2018.09.14.14.33.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Sep 2018 14:33:37 -0700 (PDT) Subject: Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW References: <1535660494.28258.36.camel@intel.com> <1535662366.28781.6.camel@intel.com> <20180831095300.GF24124@hirez.programming.kicks-ass.net> <1535726032.32537.0.camel@intel.com> <1535730524.501.13.camel@intel.com> <6d31bd30-6d5b-bbde-1e97-1d8255eff76d@linux.intel.com> <20180831162920.GQ24124@hirez.programming.kicks-ass.net> <1536957543.12990.9.camel@intel.com> <8d9ce0e9-8fc7-8c68-4aa9-9aed9ee949f2@linux.intel.com> <1536959337.12990.27.camel@intel.com> From: Dave Hansen Message-ID: <9366d924-cd67-1d2d-b78d-809bb46e7186@linux.intel.com> Date: Fri, 14 Sep 2018 14:33:36 -0700 MIME-Version: 1.0 In-Reply-To: <1536959337.12990.27.camel@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Yu-cheng Yu , Peter Zijlstra Cc: Jann Horn , the arch/x86 maintainers , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Florian Weimer , hjl.tools@gmail.com, Jonathan Corbet , keescook@chromium.org, Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , ravi.v.shankar@intel.com, vedvyas.shanbhogue@intel.com On 09/14/2018 02:08 PM, Yu-cheng Yu wrote: > On Fri, 2018-09-14 at 13:46 -0700, Dave Hansen wrote: >> On 09/14/2018 01:39 PM, Yu-cheng Yu wrote: >>> >>> With the updated ptep_set_wrprotect() below, I did MADV_WILLNEED to a shadow >>> stack of 8 MB, then 10,000 fork()'s, but could not prove it is more or less >>> efficient than the other. A So can we say this is probably fine in terms of >>> efficiency? BTW, I wasn't particularly concerned about shadow stacks. Plain old memory is affected by this change too. Right? >> Well, the first fork() will do all the hard work.A A I don't think >> subsequent fork()s will be affected. > > Are you talking about a recent commit: > > A A 1b2de5d0 mm/cow: don't bother write protecting already write-protected pages > > With that, subsequent fork()s will not do all the hard work. > However, I have not done that for shadow stack PTEs (do we want to do that?). > I think the additional benefit for shadow stack is small? You're right. mprotect() doesn't use this path. But, that reminds me, can you take a quick look at change_pte_range() and double-check that it's not affected by this issue?