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=-10.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, 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 EB813C49ED7 for ; Fri, 20 Sep 2019 14:21:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B9F412080F for ; Fri, 20 Sep 2019 14:21:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="yLfvnX9x" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387889AbfITOVP (ORCPT ); Fri, 20 Sep 2019 10:21:15 -0400 Received: from mail-ed1-f68.google.com ([209.85.208.68]:39288 "EHLO mail-ed1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387817AbfITOVP (ORCPT ); Fri, 20 Sep 2019 10:21:15 -0400 Received: by mail-ed1-f68.google.com with SMTP id a15so3922468edt.6 for ; Fri, 20 Sep 2019 07:21:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=BsObysdauMqFxQskSLuaANmrbU7y5OuxMxy3HbJkoH8=; b=yLfvnX9xGqCtoBtlknnpzBw2B3alTmNk3CXvDaf3MoBnN9PZaUdqLKOkT9Zzh/n2OZ SbD1/4Gj6cP3aQ3iwHLpmUQ2nYoif61BK45NZZpQ4xgYet8vCIJtZZ0g2qNLLsC7NQ8Z DjkOXKCNXhfgfNkhIvAiJmmSTB3991s02/L1RlMXWEpQWTyCZBRv0OCy9MJOENQS/bav 6t/uTMbrBaUhwoSZkv76hO5m1yScZU92EeaOPA4UzOax8JCzIFw23PfzQl3JBdx6KdyI hsQ4SUOsTdBkoEC4cbFw3wKzPEQvIhKU7o5rgqrJlGmwI5fBkqR0xZ8bMGc+EnyV6y67 ZWPA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=BsObysdauMqFxQskSLuaANmrbU7y5OuxMxy3HbJkoH8=; b=lYPYpvhyZWwMhE7aWxjyoDaHz3L8sNGUo5RemDJYLH+G4DZxq1qzwcsD1x2+fgswJg PFuFXsI2YXyU3jv0gMWfs75knpC1p6iKJuQO/iu0bSX53nguzrk2HVTf/dOxGTz8HVuQ e3NMS1LFx+bgQnujjL3/p0qdn4LA2t1gNjJQaptRH5m18ZNh76Y6UEJjwhh6cftRbvvb vLFwKLCF+j+QB1wznYO81cVY3qhH4zy+2+BMuGXTubl3Xd6Q5YudpFJUQReSK6O1NQ20 6m5zOQJd/G6PAGvbxCS2sbNRGhG8URkg0SW31fqIGorfCnIBSidjgF5lEipfCqRhNoON 3Arg== X-Gm-Message-State: APjAAAW63WNxvgGjvXkXafmiW/OeDW0ckCb74GAUUaBqnMvPH0hQOa0U LUv53YAwabyBb3ULWyBZhzc6CQ== X-Google-Smtp-Source: APXvYqynqm5TTKBimN51b6OZzEkRrwe+U7oN1i3ygL0xADjoA6jCeUaZdJrdhbRfLIjJwN06Jc3i/Q== X-Received: by 2002:a17:906:6d95:: with SMTP id h21mr19767726ejt.192.1568989273886; Fri, 20 Sep 2019 07:21:13 -0700 (PDT) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id g15sm352149edp.0.2019.09.20.07.21.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Sep 2019 07:21:13 -0700 (PDT) Received: by box.localdomain (Postfix, from userid 1000) id 6733D101405; Fri, 20 Sep 2019 17:21:13 +0300 (+03) Date: Fri, 20 Sep 2019 17:21:13 +0300 From: "Kirill A. Shutemov" To: Jia He Cc: Catalin Marinas , Will Deacon , Mark Rutland , James Morse , Marc Zyngier , Matthew Wilcox , "Kirill A. Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Suzuki Poulose , Punit Agrawal , Anshuman Khandual , Alex Van Brunt , Robin Murphy , Thomas Gleixner , Andrew Morton , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Ralph Campbell , hejianet@gmail.com, Kaly Xin , nd@arm.com Subject: Re: [PATCH v7 3/3] mm: fix double page fault on arm64 if PTE_AF is cleared Message-ID: <20190920142113.52mdiflo4yghlsmu@box> References: <20190920135437.25622-1-justin.he@arm.com> <20190920135437.25622-4-justin.he@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190920135437.25622-4-justin.he@arm.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 20, 2019 at 09:54:37PM +0800, Jia He wrote: > When we tested pmdk unit test [1] vmmalloc_fork TEST1 in arm64 guest, there > will be a double page fault in __copy_from_user_inatomic of cow_user_page. > > Below call trace is from arm64 do_page_fault for debugging purpose > [ 110.016195] Call trace: > [ 110.016826] do_page_fault+0x5a4/0x690 > [ 110.017812] do_mem_abort+0x50/0xb0 > [ 110.018726] el1_da+0x20/0xc4 > [ 110.019492] __arch_copy_from_user+0x180/0x280 > [ 110.020646] do_wp_page+0xb0/0x860 > [ 110.021517] __handle_mm_fault+0x994/0x1338 > [ 110.022606] handle_mm_fault+0xe8/0x180 > [ 110.023584] do_page_fault+0x240/0x690 > [ 110.024535] do_mem_abort+0x50/0xb0 > [ 110.025423] el0_da+0x20/0x24 > > The pte info before __copy_from_user_inatomic is (PTE_AF is cleared): > [ffff9b007000] pgd=000000023d4f8003, pud=000000023da9b003, pmd=000000023d4b3003, pte=360000298607bd3 > > As told by Catalin: "On arm64 without hardware Access Flag, copying from > user will fail because the pte is old and cannot be marked young. So we > always end up with zeroed page after fork() + CoW for pfn mappings. we > don't always have a hardware-managed access flag on arm64." > > This patch fix it by calling pte_mkyoung. Also, the parameter is > changed because vmf should be passed to cow_user_page() > > Add a WARN_ON_ONCE when __copy_from_user_inatomic() returns error > in case there can be some obscure use-case.(by Kirill) > > [1] https://github.com/pmem/pmdk/tree/master/src/test/vmmalloc_fork > > Reported-by: Yibo Cai > Signed-off-by: Jia He Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov