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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 BD0AFC4321A for ; Wed, 10 Mar 2021 16:58:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A34A464FC6 for ; Wed, 10 Mar 2021 16:58:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233712AbhCJQ5k (ORCPT ); Wed, 10 Mar 2021 11:57:40 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:31289 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233399AbhCJQ5S (ORCPT ); Wed, 10 Mar 2021 11:57:18 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615395438; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=sH8IQrZxuYeOUbLZE/57xl+lGLw/UXV3S3e87t66hh4=; b=c/Uejp7vuOL7gdap/GfmDX778VTG+l4+/6Q/QfHQ3zRVWxv/D/tpK2puGpmB7z4rYJP14/ y67XaYH7KVujE3/TrbL9NLtsL+racd5SemSVyvn8y6zSk6MfG1QvDqnAuNFxZgolcitnqH n7/hjYUJihM6SddAVn0zwniYfTBut7E= Received: from mail-qv1-f69.google.com (mail-qv1-f69.google.com [209.85.219.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-65-smEmGA65NfyyeRjTFXeOZw-1; Wed, 10 Mar 2021 11:57:16 -0500 X-MC-Unique: smEmGA65NfyyeRjTFXeOZw-1 Received: by mail-qv1-f69.google.com with SMTP id h10so13128484qvf.19 for ; Wed, 10 Mar 2021 08:57:16 -0800 (PST) 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; bh=sH8IQrZxuYeOUbLZE/57xl+lGLw/UXV3S3e87t66hh4=; b=JjI8UDKE3Bf4pM1AI3ilvgZG6nJOaGXzYDO5065t+knJhJdhr1oIrnQYhg+vQwE5Ok +7OxQ4HkL3HAPh7prRUPMOhYGC0piT3yUbIR5qL/eR9rW9hY5fvdUT1TzKBb+XAe2ege vVcyIprzCA76LQoPzWMlInyU7D/nHed2O99RCb+qn6vEdWsKy7Viv34sV8lMsfMGfuzc Kh6DPINTwDLyxCqiZG0zz2EYc3YWCGx5VSzJosLcKGxykmPqB+J27DrCvUKOHK6cDn4f oPCnT3x8RfnLeE99f0f+f1gvSvH8aG1BNuNNT6y3AWa8wgdJ/+6XuLDUa9/66h/gYiod Po5A== X-Gm-Message-State: AOAM533BvPniHXq3HChA0IC4N+HfMxyu1hWLjeZethx0zWpzU7qMdVoX kEzSkyEsMdvItYPhXk8CNs2SwgKcBiuDRos66U/V02YyoZbyPamlQLK4DGziNYBZfZogI1qyyew sgx1luyZZnmIHhO/jMCWhfEDB X-Received: by 2002:ac8:4749:: with SMTP id k9mr2371966qtp.44.1615395435976; Wed, 10 Mar 2021 08:57:15 -0800 (PST) X-Google-Smtp-Source: ABdhPJy3DSqfvNYFn7nY1WxbUtcI1yp3w27QNJwctoj81/6+xlgC0vsC2oq13zfz4EdeeuHAO5YHEQ== X-Received: by 2002:ac8:4749:: with SMTP id k9mr2371950qtp.44.1615395435682; Wed, 10 Mar 2021 08:57:15 -0800 (PST) Received: from xz-x1 ([142.126.89.138]) by smtp.gmail.com with ESMTPSA id m21sm12908202qka.28.2021.03.10.08.57.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Mar 2021 08:57:15 -0800 (PST) Date: Wed, 10 Mar 2021 11:57:13 -0500 From: Peter Xu To: Naresh Kamboju Cc: Linux-Next Mailing List , open list , linux-mm , Andrea Arcangeli , Axel Rasmussen , Mike Rapoport , "Kirill A . Shutemov" , Andrew Morton , Matthew Wilcox , Mike Kravetz , lkft-triage@lists.linaro.org, Arnd Bergmann , Stephen Rothwell Subject: Re: [PATCH v4 2/4] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled Message-ID: <20210310165713.GB6530@xz-x1> References: <20210218230633.15028-1-peterx@redhat.com> <20210218231202.15426-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="tKW2IUtsqtDRztdT" Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --tKW2IUtsqtDRztdT Content-Type: text/plain; charset=utf-8 Content-Disposition: inline On Wed, Mar 10, 2021 at 01:18:42PM +0530, Naresh Kamboju wrote: > Hi Peter, Hi, Naresh, > > On Fri, 19 Feb 2021 at 04:43, Peter Xu wrote: > > > > Huge pmd sharing could bring problem to userfaultfd. The thing is that > > userfaultfd is running its logic based on the special bits on page table > > entries, however the huge pmd sharing could potentially share page table > > entries for different address ranges. That could cause issues on either: > > > > - When sharing huge pmd page tables for an uffd write protected range, the > > newly mapped huge pmd range will also be write protected unexpectedly, or, > > > > - When we try to write protect a range of huge pmd shared range, we'll first > > do huge_pmd_unshare() in hugetlb_change_protection(), however that also > > means the UFFDIO_WRITEPROTECT could be silently skipped for the shared > > region, which could lead to data loss. > > > > Since at it, a few other things are done altogether: > > > > - Move want_pmd_share() from mm/hugetlb.c into linux/hugetlb.h, because > > that's definitely something that arch code would like to use too > > > > - ARM64 currently directly check against CONFIG_ARCH_WANT_HUGE_PMD_SHARE when > > trying to share huge pmd. Switch to the want_pmd_share() helper. > > > > Since at it, move vma_shareable() from huge_pmd_share() into want_pmd_share(). > > > > Reviewed-by: Mike Kravetz > > Reviewed-by: Axel Rasmussen > > Signed-off-by: Peter Xu > > --- > > arch/arm64/mm/hugetlbpage.c | 3 +-- > > include/linux/hugetlb.h | 2 ++ > > include/linux/userfaultfd_k.h | 9 +++++++++ > > mm/hugetlb.c | 20 ++++++++++++++------ > > 4 files changed, 26 insertions(+), 8 deletions(-) > > > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c > > index 6e3bcffe2837..58987a98e179 100644 > > --- a/arch/arm64/mm/hugetlbpage.c > > +++ b/arch/arm64/mm/hugetlbpage.c > > @@ -284,8 +284,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma, > > */ > > ptep = pte_alloc_map(mm, pmdp, addr); > > } else if (sz == PMD_SIZE) { > > - if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) && > > - pud_none(READ_ONCE(*pudp))) > > + if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp))) > > While building Linux next 20210310 tag for arm64 architecture with > > - CONFIG_ARM64_64K_PAGES=y > > enabled the build failed due to below errors / warnings > > make --silent --keep-going --jobs=8 > O=/home/tuxbuild/.cache/tuxmake/builds/1/tmp ARCH=arm64 > CROSS_COMPILE=aarch64-linux-gnu- 'CC=sccache aarch64-linux-gnu-gcc' > 'HOSTCC=sccache gcc' > aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected! > aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected! > aarch64-linux-gnu-ld: arch/arm64/mm/hugetlbpage.o: in function `huge_pte_alloc': > hugetlbpage.c:(.text+0x7d8): undefined reference to `want_pmd_share' > > Reported-by: Naresh Kamboju Sorry for the issue & thanks for the report. Would you please check whether the patch attached could fix the issue? -- Peter Xu --tKW2IUtsqtDRztdT Content-Type: text/plain; charset=utf-8 Content-Disposition: attachment; filename="0001-mm-hugetlb-Fix-build-with-ARCH_WANT_HUGE_PMD_SHARE.patch" >From 4072042b415d1f78ac1ab017671e345b414ca6ab Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Wed, 10 Mar 2021 11:48:56 -0500 Subject: [PATCH] mm/hugetlb: Fix build with !ARCH_WANT_HUGE_PMD_SHARE want_pmd_share() is undefined with !ARCH_WANT_HUGE_PMD_SHARE since it's put by accident into a "#ifdef ARCH_WANT_HUGE_PMD_SHARE" block. Moving it out won't work either since vma_shareable() is only defined within the block. Define it for !ARCH_WANT_HUGE_PMD_SHARE instead. Fixes: 5b109cc1cdcc ("hugetlb/userfaultfd: forbid huge pmd sharing when uffd enabled") Cc: Andrew Morton Cc: Mike Kravetz Cc: Axel Rasmussen Reported-by: Naresh Kamboju Signed-off-by: Peter Xu --- mm/hugetlb.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index d58f1456fe27..8dda7e034477 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5469,9 +5469,6 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) { -#ifndef CONFIG_ARCH_WANT_HUGE_PMD_SHARE - return false; -#endif #ifdef CONFIG_USERFAULTFD if (uffd_disable_huge_pmd_share(vma)) return false; @@ -5616,6 +5613,11 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, unsigned long *start, unsigned long *end) { } + +bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) +{ + return false; +} #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB -- 2.26.2 --tKW2IUtsqtDRztdT--