Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04CC1C433F5 for ; Tue, 21 Dec 2021 15:53:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231927AbhLUPxt (ORCPT ); Tue, 21 Dec 2021 10:53:49 -0500 Received: from mga03.intel.com ([134.134.136.65]:28756 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229449AbhLUPxr (ORCPT ); Tue, 21 Dec 2021 10:53:47 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1640102027; x=1671638027; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=R5238Kbi1+5NFWk9tUibKnCtpKSEaKH/BRg0ie3MMR8=; b=OdMrrRqaXkGdNJga19OgfsA/EFB7LuUIfmhLdqq7FSnBIs77CKD0clX6 qwyss9/DP8q3kDroujQG+xhWdVV0fXM0YLNpWemLizf8w5mi1+J3Xo2f/ Ez6Ebd2kT6aL8xf6zHKqXf5A71xJizUioao66BF52gJ3E5adj56FhThTB GrjzFd4VR2wqvELXXuFw46g01qHYCU2svPGlMhvt089vrd6KjPUcYJo85 qFYtJ+3wgQhQdJ324RRFqugJbK5e8JOvsiJyAzZl6AmLf3olYvZ5WnLpx NGeojzXi8jkialZ2gJ4SRhJ7n+u420BJ2YAKcQrKNtyqUMSCzYp3eWKIm w==; X-IronPort-AV: E=McAfee;i="6200,9189,10204"; a="240371609" X-IronPort-AV: E=Sophos;i="5.88,223,1635231600"; d="scan'208";a="240371609" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Dec 2021 07:53:42 -0800 X-IronPort-AV: E=Sophos;i="5.88,223,1635231600"; d="scan'208";a="466335481" Received: from jborouma-mobl1.amr.corp.intel.com (HELO [10.209.37.145]) ([10.209.37.145]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Dec 2021 07:53:41 -0800 Subject: Re: [PATCH 1/2] x86/sgx: Add accounting for tracking overcommit To: Borislav Petkov , Kristen Carlson Accardi Cc: linux-sgx@vger.kernel.org, Jonathan Corbet , Jarkko Sakkinen , Dave Hansen , Thomas Gleixner , Ingo Molnar , x86@kernel.org, "H. Peter Anvin" , lkml References: <20211220174640.7542-1-kristen@linux.intel.com> <20211220174640.7542-2-kristen@linux.intel.com> <9e08e13208950e9fd955a46994b7fef705751dd6.camel@linux.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@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: <721375d1-c76a-24fa-5013-f7b2455610a2@intel.com> Date: Tue, 21 Dec 2021 07:53:38 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/20/21 2:48 PM, Borislav Petkov wrote: > On Mon, Dec 20, 2021 at 01:35:03PM -0800, Kristen Carlson Accardi wrote: >> So, in your proposal you would first change the calculated number of >> maximum available backing pages to be based on total system RAM rather >> than EPC memory, got it. > > This was just an example. My point is to try to make it automatic and > not introduce another knob. And to decide on the limits and behavior > by using common sense and addressing the common use cases first. The common case is clearly a few enclaves on systems where the overcommit levels are modest. The "100%" limit will work great there. I'd personally be fine with just enforcing that limit as the default and ignoring everything else. It makes me a bit nervous, though, because suddenly enforcing a limit is an ABI break. The tunable effectively gives us a way out if we screw up either the limit's quantity or someone needs the old ABI back. That said, we don't *need* it to be tunable, boot parameter or not. If you're concerned about the tunable, I think we should drop it and not look back. > Imagine you're a sysadmin. Or a general, common system user if there > ever is one. > > When your system starts thrashing and you're running a bunch of > enclaves, how do you find out there even is a knob which might > potentially help you? I'm selfish. The tunable isn't for end users. It's for me. The scenario I envisioned is that a user upgrades to a new kernel and their enclaves start crashing. They'll eventually find us, the maintainers of the SGX code, and we'll have a tool as kernel developers to help them. The tunable helps _me_ in two ways: 1. It help me easily get user back to pre-5.17 (or whatever) behavior 2. If we got the "100%" value wrong, end users can help us experiment to help find a better value. BTW, all the chat about "malicious" enclaves and so forth... I *totally* agree that this is a problem and one worth solving. It just can't be solved today. We need real cgroup support. It's coming soon.