From patchwork Fri Feb 12 21:53:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12086145 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 BB9BBC433E0 for ; Fri, 12 Feb 2021 21:56:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B00864E8A for ; Fri, 12 Feb 2021 21:56:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229660AbhBLVzy (ORCPT ); Fri, 12 Feb 2021 16:55:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230270AbhBLVzi (ORCPT ); Fri, 12 Feb 2021 16:55:38 -0500 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 421AAC06178B for ; Fri, 12 Feb 2021 13:54:23 -0800 (PST) Received: by mail-pg1-x54a.google.com with SMTP id c30so778275pgl.15 for ; Fri, 12 Feb 2021 13:54:23 -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=YlfIormFBY/rysSGqj+ed5treI/R2/QqIMyWcQNPNXw=; b=CTA6VBPTeFoAytyEos3lFWsVfDnGleeYtmq/FweYdKvW2QZB2YOJ2iA5510aDYkwwm f1M4M0HXg164r7mCCQYA8E96Khx3lIUmOQCYKUU6G88yAzBKEo21KmMcQvRZeWO37DMT GuCm3Juq29cIL78PNFnwnb1evyu9ZvJY7rMy4EV+45WqOfBr00LinEOZ0kn4BPWi1s/v IsevNgCw4AzhAORs6F1A/oWmx8boULq3Uhrrc269HT0dzBi5x3fTSVlMO+xQ5ZMxjK7L E70c3DKqkObmpcmJsSksnqXlyE/pVf++EDEpmdEg0e2ecnMT9pcJVoet4SwErpYyG2sZ zHzQ== 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=YlfIormFBY/rysSGqj+ed5treI/R2/QqIMyWcQNPNXw=; b=axRlK7mz/KWyByc/m33NGoVsqudkw/rHpFI08zAxHRMUAkFHcFnh95pQfKFWKRYmrY yaaXNT9JW7+/zhfvhoVbV3zxNLMOKTBk+It1Rg7tx1xKJ6Q0fdBlq3GwTVKN4QpH5YHf m2DwNgqwjt7jtPLlmR3uxb17YtbblxzIlNKPL8JAxya61zW5wjIN+D8aBryqtqVz5iNv ZMoS/gDbeKOCnFm6bQxWhBBp0G69eHaJef1gys9Qdxwx9WF1FC+bDIaw+TH7/1Yw0vDs owelHYfmWorWXNms4T0nh/PvIU0pDTt1eHCWHQYjlzxslJ2o4Eo8GHEErdzbshoUliuC NNkA== X-Gm-Message-State: AOAM533E6Tdtx56/NrOGUszMQfmBGZiGkhSvBJ38GePy9Wz4RmyaK6kh +5YVWE+YAUwTtO4AxqWGxj3rcCTLgzSptBJa4JmL X-Google-Smtp-Source: ABdhPJwGFRdVdg0cd7jePQFHLBhd+X3gZzHYFwdheoONEE1KBWOaidn+Vm+YQFlcd9yaV231OScKlUtfWhrhA94tO2JM Sender: "axelrasmussen via sendgmr" X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:d2f:99bb:c1e0:34ba]) (user=axelrasmussen job=sendgmr) by 2002:a63:da4a:: with SMTP id l10mr5133633pgj.222.1613166862664; Fri, 12 Feb 2021 13:54:22 -0800 (PST) Date: Fri, 12 Feb 2021 13:53:59 -0800 In-Reply-To: <20210212215403.3457686-1-axelrasmussen@google.com> Message-Id: <20210212215403.3457686-4-axelrasmussen@google.com> Mime-Version: 1.0 References: <20210212215403.3457686-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.30.0.478.g8a0d178c01-goog Subject: [PATCH v6 3/7] userfaultfd: disable huge PMD sharing for minor fault 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_Koutn=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 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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. Signed-off-by: Axel Rasmussen --- include/linux/userfaultfd_k.h | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 4e03268c65ec..98cb6260b4b4 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -62,15 +62,6 @@ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx; } -/* - * Never enable huge pmd sharing on uffd-wp registered vmas, because uffd-wp - * protect information is per pgtable entry. - */ -static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma) -{ - return vma->vm_flags & VM_UFFD_WP; -} - static inline bool userfaultfd_missing(struct vm_area_struct *vma) { return vma->vm_flags & VM_UFFD_MISSING; @@ -83,6 +74,23 @@ static inline bool userfaultfd_wp(struct vm_area_struct *vma) bool userfaultfd_minor(struct vm_area_struct *vma); +/* + * Never enable huge pmd sharing on some uffd registered vmas: + * + * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry. + * + * - VM_UFFD_MISSING VMAs with UFFD_FEATURE_MINOR_HUGETLBFS, 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 userfaultfd_wp(vma) || userfaultfd_minor(vma); +} + static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma, pte_t pte) {