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=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 F18D4C432BE for ; Thu, 12 Aug 2021 20:59:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9618060E9B for ; Thu, 12 Aug 2021 20:59:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9618060E9B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 0A45C6B006C; Thu, 12 Aug 2021 16:59:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 054576B0071; Thu, 12 Aug 2021 16:59:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E5DCA6B0072; Thu, 12 Aug 2021 16:59:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0019.hostedemail.com [216.40.44.19]) by kanga.kvack.org (Postfix) with ESMTP id C94DC6B006C for ; Thu, 12 Aug 2021 16:59:07 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 733DA1804DAD0 for ; Thu, 12 Aug 2021 20:59:07 +0000 (UTC) X-FDA: 78467643534.22.9FCE03A Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by imf18.hostedemail.com (Postfix) with ESMTP id 88D43401006C for ; Thu, 12 Aug 2021 20:59:06 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10074"; a="202609915" X-IronPort-AV: E=Sophos;i="5.84,316,1620716400"; d="scan'208";a="202609915" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Aug 2021 13:59:04 -0700 X-IronPort-AV: E=Sophos;i="5.84,316,1620716400"; d="scan'208";a="517619937" Received: from wtharris-mobl1.amr.corp.intel.com (HELO [10.209.22.190]) ([10.209.22.190]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Aug 2021 13:59:03 -0700 Subject: Re: [PATCH 1/5] mm: Add support for unaccepted memory To: "Kirill A. Shutemov" Cc: Joerg Roedel , Andi Kleen , Borislav Petkov , Andy Lutomirski , Sean Christopherson , Andrew Morton , Kuppuswamy Sathyanarayanan , David Rientjes , Vlastimil Babka , Tom Lendacky , Thomas Gleixner , Peter Zijlstra , Paolo Bonzini , Ingo Molnar , Varad Gautam , Dario Faggioli , x86@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" References: <20210810062626.1012-1-kirill.shutemov@linux.intel.com> <20210810062626.1012-2-kirill.shutemov@linux.intel.com> <9748c07c-4e59-89d0-f425-c57f778d1b42@linux.intel.com> <17b6a3a3-bd7d-f57e-8762-96258b16247a@intel.com> <796a4b20-7fa3-3086-efa0-2f728f35ae06@linux.intel.com> <3caf5e73-c104-0057-680c-7851476e67ac@linux.intel.com> <25312492-5d67-e5b0-1a51-b6880f45a550@intel.com> <20210812204924.haneuxapkmluli6t@box.shutemov.name> 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: <708c758f-2305-4fe6-ddcd-6881794402a5@intel.com> Date: Thu, 12 Aug 2021 13:59:01 -0700 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: <20210812204924.haneuxapkmluli6t@box.shutemov.name> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Authentication-Results: imf18.hostedemail.com; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none); spf=none (imf18.hostedemail.com: domain of dave.hansen@intel.com has no SPF policy when checking 134.134.136.126) smtp.mailfrom=dave.hansen@intel.com X-Stat-Signature: hqqw3myq8fp3jxket5idhoprddtbm38e X-Rspamd-Queue-Id: 88D43401006C X-Rspamd-Server: rspam05 X-HE-Tag: 1628801946-473722 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 8/12/21 1:49 PM, Kirill A. Shutemov wrote: > On Thu, Aug 12, 2021 at 07:14:20AM -0700, Dave Hansen wrote: >> On 8/12/21 1:19 AM, Joerg Roedel wrote: >> maybe_accept_page() >> { >> unsigned long huge_pfn =3D page_to_phys(page) / PMD_SIZE; >> >> /* Test the bit before taking any locks: */ >> if (test_bit(huge_pfn, &accepted_bitmap)) >> return; >> >> spin_lock_irq(); >> /* Retest inside the lock: */ >> if (test_bit(huge_pfn, &accepted_bitmap)) >> return; >> tdx_accept_page(page, PMD_SIZE); >> set_bit(huge_pfn, &accepted_bitmap)); >> spin_unlock_irq(); >> } >> >> That's still not great. It's still a global lock and the lock is stil= l >> held for quite a while because that accept isn't going to be lightning >> fast. But, at least it's not holding any *other* locks. It also >> doesn't take any locks in the fast path where the 2MB page was already >> accepted. >=20 > I expect a cache line with bitmap to bounce around during warm up. One > cache line covers a gig of RAM. The bitmap bouncing around isn't going to really matter when you have a global lock protecting it from writes. > It's also not clear at all at what point the static key has to be > switched. We don't have any obvious point where we can say we are done > with accepting (unless you advocate for proactive accepting). Two easy options: 1. Run over the bitmap and counts the bits left. That can be done outside the lock even. 2. Keep a counter of the number of bits set in the bitmap. > I like PageOffline() because we only need to consult the cache page > allocator already have in hands before looking into bitmap. I like it too. But, it's really nasty if the value is only valid deep in the allocator. We could keep the PageOffline() thing and then move it to some other field in 'struct page' that's only valid between ClearPageOffline() and prep_new_page(). Some magic value that says: "This page has not yet been accepted, you better check the bitmap." Something like: if (TestClearPageOffline(page)) page->private =3D 0Xdeadbeef; and then check page->private in prep_new_page(). There should be plenty of 'struct page' space to hijack in that small window. BTW, I was going to actually try and hack something up, but I got annoyed that your patches don't apply upstream and gave up. A git tree with all of the dependencies would be nice.