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=-16.6 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 27801C433E0 for ; Wed, 10 Feb 2021 21:22:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BF47D64ED0 for ; Wed, 10 Feb 2021 21:22:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF47D64ED0 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 263166B007B; Wed, 10 Feb 2021 16:22:20 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 179248D0001; Wed, 10 Feb 2021 16:22:20 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 03F906B007E; Wed, 10 Feb 2021 16:22:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0007.hostedemail.com [216.40.44.7]) by kanga.kvack.org (Postfix) with ESMTP id D01596B007B for ; Wed, 10 Feb 2021 16:22:19 -0500 (EST) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 934521823548C for ; Wed, 10 Feb 2021 21:22:19 +0000 (UTC) X-FDA: 77803631598.12.quilt01_061642427613 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin12.hostedemail.com (Postfix) with ESMTP id 74ED818049B85 for ; Wed, 10 Feb 2021 21:22:19 +0000 (UTC) X-HE-Tag: quilt01_061642427613 X-Filterd-Recvd-Size: 5991 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Wed, 10 Feb 2021 21:22:18 +0000 (UTC) Received: by mail-yb1-f202.google.com with SMTP id v17so3924114ybq.9 for ; Wed, 10 Feb 2021 13:22:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=C7eX4+NVGX5He9yBXKDzK09THiAFk9zxs8Mq4BgC9+k=; b=X4O2XnKeTyP1mrCdcCUv43l+RzH7IHrvPnQey/wsi4M+B7W6hzZlGZRvvKHgHPwxwy /WvTVU9Ez2URRDEtOOJilnHqyhVt6olC/GaNJXdnpvVpPBeGB4gNunb7ZQQAvUfzsdxe edZieAb5VYpDFXolL8aMA/zf1+cab8/dJJYDrbwRG+GaG11wlghI8k3l4/uai0ppkIOY VRGXu6go8MCoW4HFmNHNxwfTbMwbVHMUk2ma8RoEvXxXQ4B5PVnkOj5fjrgRZZ2y3LAP 0DBfUQeu/ImT99KF9thtVNcUbahpM0amXl0cGg6p/tFca2fEUDbwL7TN4RyPqcPqmPCr FDgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=C7eX4+NVGX5He9yBXKDzK09THiAFk9zxs8Mq4BgC9+k=; b=j2srO/nJUh0gdyN06HYiF+5CAQKyHY4mEsILB76plogYHlZ8orsVrt2BdgvYfHgEWt mdYDQJsS/TbqP2GYpljw40e4VXxstJrr3ERCzy/untbFkwmJvH+d1xfCBOJMT6ZmN9RU QNU0qgRQHDb2pKi2XRKK0ryDH/2wGa11eM3p5VXZwNfsWA0cbu/7Wqnpv/puqdmQW25p r4BpoFAKceMbkKAmJIaYRXJIXTSaaVmhWCfmGOBxa7oJ8DGcbxyMz7gOZ8tk9s+iXDev eycp2YYXxoRlQpaI66tB79Yrba3RpEuShOfJlmI08s8nt4neymVwMjKvZU2yB6wfnET3 3ThA== X-Gm-Message-State: AOAM531tkmj5q+H2HjoVXKwnBitpBWN51bDmg/6Q2ehdTCaqmRCy/ZBE Hub6t9Ln3HNaAhQQOFpL4smNi/rBs6x6B4sxbXAl X-Google-Smtp-Source: ABdhPJwagtVWNE35dh8EXmqH56OhS+dAouO564OVOUkNaVQb6+9yLc/FG1bX+ngeJuwo0ZOZsUjMFDiVvTAXntctl3Gj X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:94ee:de01:168:9f20]) (user=axelrasmussen job=sendgmr) by 2002:a25:cc46:: with SMTP id l67mr7659356ybf.16.1612992138150; Wed, 10 Feb 2021 13:22:18 -0800 (PST) Date: Wed, 10 Feb 2021 13:21:56 -0800 In-Reply-To: <20210210212200.1097784-1-axelrasmussen@google.com> Message-Id: <20210210212200.1097784-7-axelrasmussen@google.com> Mime-Version: 1.0 References: <20210210212200.1097784-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.30.0.478.g8a0d178c01-goog Subject: [PATCH v5 06/10] userfaultfd: disable huge PMD sharing for MINOR registered VMAs From: Axel Rasmussen To: Alexander Viro , Alexey Dobriyan , Andrea Arcangeli , Andrew Morton , Anshuman Khandual , Catalin Marinas , Chinwen Chang , Huang Ying , Ingo Molnar , Jann Horn , Jerome Glisse , Lokesh Gidra , "Matthew Wilcox (Oracle)" , Michael Ellerman , "=?UTF-8?q?Michal=20Koutn=C3=BD?=" , Michel Lespinasse , Mike Kravetz , Mike Rapoport , Nicholas Piggin , Peter Xu , Shaohua Li , Shawn Anastasio , Steven Rostedt , Steven Price , Vlastimil Babka Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Adam Ruprecht , Axel Rasmussen , Cannon Matthews , "Dr . David Alan Gilbert" , David Rientjes , Mina Almasry , Oliver Upton Content-Type: text/plain; charset="UTF-8" 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: As the comment says: for the MINOR fault use case, although the page might be present and populated in the other (non-UFFD-registered) half of the mapping, it may be out of date, and we explicitly want userspace to get a minor fault so it can check and potentially update the page's contents. Huge PMD sharing would prevent these faults from occurring for suitably aligned areas, so disable it upon UFFD registration. Reviewed-by: Peter Xu Signed-off-by: Axel Rasmussen --- include/linux/userfaultfd_k.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 0390e5ac63b3..e060d5f77cc5 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -56,12 +56,19 @@ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, } /* - * Never enable huge pmd sharing on uffd-wp registered vmas, because uffd-wp - * protect information is per pgtable entry. + * Never enable huge pmd sharing on some uffd registered vmas: + * + * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry. + * + * - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for + * VMAs which share huge pmds. (If you have two mappings to the same + * underlying pages, and fault in the non-UFFD-registered one with a write, + * with huge pmd sharing this would *also* setup the second UFFD-registered + * mapping, and we'd not get minor faults.) */ static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma) { - return vma->vm_flags & VM_UFFD_WP; + return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR); } static inline bool userfaultfd_missing(struct vm_area_struct *vma) -- 2.30.0.478.g8a0d178c01-goog