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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 E13F7C433E2 for ; Mon, 6 Jul 2020 17:21:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B106520720 for ; Mon, 6 Jul 2020 17:21:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594056061; bh=rp3iLbG4NzFQ6srRlKxeSGp+kPRUVlRaIbnd6z2D5UY=; h=From:To:Cc:Subject:Date:List-ID:From; b=HQZZ+jliGky9Dh1onIVYghvjIMjQregVcDj26ODxtoA57kct/9iWPpanOGz/biYuy OoTu4xKc3UBsNUnVXSQIvpSv+nZEUy7XgYcAte0eF4joCrOyoE2sZNf0+pY9lAr359 saLSNGa0RDEuA7j0bi/CAzK/O/vtrixIWlaJPiaQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729657AbgGFRVA (ORCPT ); Mon, 6 Jul 2020 13:21:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:55272 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729478AbgGFRVA (ORCPT ); Mon, 6 Jul 2020 13:21:00 -0400 Received: from aquarius.haifa.ibm.com (nesher1.haifa.il.ibm.com [195.110.40.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 28431206CD; Mon, 6 Jul 2020 17:20:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594056059; bh=rp3iLbG4NzFQ6srRlKxeSGp+kPRUVlRaIbnd6z2D5UY=; h=From:To:Cc:Subject:Date:From; b=l76C5n6D647knTaiC1Ofb1gHincOwMnY9GaLtoXpCGO4qWLWz68KmJY4gVJQ/6d/k VR/PWu6VIqUgb9u1FiEtG5Gf3RnfhjbueTLXu9dsFSDOZ2ky6V19VYmfJjX5c3HeU/ pCMYh7UCO/5pYVrWEUvl/qjqN1iCeEqppXWkAh9c= From: Mike Rapoport To: linux-kernel@vger.kernel.org Cc: Alan Cox , Andrew Morton , Andy Lutomirski , Christopher Lameter , Dave Hansen , Idan Yaniv , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Peter Zijlstra , "Reshetova, Elena" , Thomas Gleixner , Tycho Andersen , linux-api@vger.kernel.org, linux-mm@kvack.org, Mike Rapoport Subject: [RFC PATCH v2 0/5] mm: extend memfd with ability to create "secret" memory areas Date: Mon, 6 Jul 2020 20:20:46 +0300 Message-Id: <20200706172051.19465-1-rppt@kernel.org> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mike Rapoport Hi, This is a second version of "secret" mappings implementation backed by a file descriptor. The file descriptor is created using memfd_create() syscall with a new MFD_SECRET flag. The file descriptor should be configured using ioctl() to define the desired protection and then mmap() of the fd will create a "secret" memory mapping. The pages in that mapping will be marked as not present in the direct map and will have desired protection bits set in the user page table. For instance, current implementation allows uncached mappings. Hiding secret memory mappings behind an anonymous file allows (ab)use of the page cache for tracking pages allocated for the "secret" mappings as well as using address_space_operations for e.g. page migration callbacks. The anonymous file may be also used implicitly, like hugetlb files, to implement mmap(MAP_SECRET) and use the secret memory areas with "native" mm ABIs. As the fragmentation of the direct map was one of the major concerns raised during the previous postings, I've added an amortizing cache of PMD-size pages to each file descriptor and an ability to reserve large chunks of the physical memory at boot time and then use this memory as an allocation pool for the secret memory areas. In addition, I've tried to find some numbers that show the benefit of using larger pages in the direct map, but I couldn't find anything so I've run a couple of benchmarks from phoronix-test-suite on my laptop (i7-8650U with 32G RAM). I've tested three variants: the default with 28G of the physical memory covered with 1G pages, then I disabled 1G pages using "nogbpages" in the kernel command line and at last I've forced the entire direct map to use 4K pages using a simple patch to arch/x86/mm/init.c. I've made runs of the benchmarks with SSD and tmpfs. Surprisingly, the results does not show huge advantage for large pages. For instance, here the results for kernel build with 'make -j8', in seconds: | 1G | 2M | 4K ------------------------+--------+--------+--------- ssd, mitigations=on | 308.75 | 317.37 | 314.9 ssd, mitigations=off | 305.25 | 295.32 | 304.92 ram, mitigations=on | 301.58 | 322.49 | 306.54 ram, mitigations=off | 299.32 | 288.44 | 310.65 All the results I have are available at [1]. If anybody is interested in plain text, please let me know. [1] https://docs.google.com/spreadsheets/d/1tdD-cu8e93vnfGsTFxZ5YdaEfs2E1GELlvWNOGkJV2U/edit?usp=sharing Mike Rapoport (5): mm: make HPAGE_PxD_{SHIFT,MASK,SIZE} always available mmap: make mlock_future_check() global mm: extend memfd with ability to create "secret" memory areas mm: secretmem: use PMD-size pages to amortize direct map fragmentation mm: secretmem: add ability to reserve memory at boot include/linux/huge_mm.h | 10 +- include/linux/memfd.h | 9 + include/uapi/linux/magic.h | 1 + include/uapi/linux/memfd.h | 6 + mm/Kconfig | 3 + mm/Makefile | 1 + mm/internal.h | 3 + mm/memfd.c | 10 +- mm/mmap.c | 5 +- mm/secretmem.c | 445 +++++++++++++++++++++++++++++++++++++ 10 files changed, 480 insertions(+), 13 deletions(-) create mode 100644 mm/secretmem.c base-commit: 7c30b859a947535f2213277e827d7ac7dcff9c84 -- 2.26.2