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=-16.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,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 C34C1C4708F for ; Thu, 27 May 2021 20:23:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 71C2B613E2 for ; Thu, 27 May 2021 20:23:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 71C2B613E2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 956C06B007E; Thu, 27 May 2021 16:23:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8FBF16B0083; Thu, 27 May 2021 16:23:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 383076B0085; Thu, 27 May 2021 16:23:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0064.hostedemail.com [216.40.44.64]) by kanga.kvack.org (Postfix) with ESMTP id E9DF06B007E for ; Thu, 27 May 2021 16:23:37 -0400 (EDT) Received: from smtpin40.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 87CC58249980 for ; Thu, 27 May 2021 20:23:37 +0000 (UTC) X-FDA: 78188136474.40.6B1B242 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf14.hostedemail.com (Postfix) with ESMTP id 75293C00774F for ; Thu, 27 May 2021 20:23:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622147016; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oBNk7u3ivtT+37hOCTF6A87HkSdxXSKsCgL3KlLLZ5E=; b=NrjOfxutEfS/cS38IWBQiOqz0C4sJGsJoHXO/JI6dbjkll2mdu7PWt1+1CMtAr8glMGzuj QYTVXcbtNaF4SVzfjq+SGny2H8ku/Jm2uTNeQpGDzZHkLm6Hd41jBFKdgkk57E7SpBpEFo HdPLDETSirb4ncmNMfDWG3o6mg8jpdM= Received: from mail-qv1-f72.google.com (mail-qv1-f72.google.com [209.85.219.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-411-r-m7kmY5Oq-_DLKgOiRbkg-1; Thu, 27 May 2021 16:23:33 -0400 X-MC-Unique: r-m7kmY5Oq-_DLKgOiRbkg-1 Received: by mail-qv1-f72.google.com with SMTP id j14-20020a0cf30e0000b02902142ba51ef2so1022610qvl.10 for ; Thu, 27 May 2021 13:23:32 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=oBNk7u3ivtT+37hOCTF6A87HkSdxXSKsCgL3KlLLZ5E=; b=AP4NqQZb5yWIIrywexMKaSCBQbsEkRj2i4ndgQV3ds9uLFR/K60eemIcYD/q/5LVCQ 3bMeaUspeq0hAPakYjkMCefi8IemzvaKtb+3s+IP2MLEVUCfHRobRVn7kXBFhvh5G3Eo akbKGmO0KDIdT+lQIedTKqYClAyahIfAbsTeKxbt88RsgZ6JJ/9e5AqxvAAllhzGIzVl Rio7RbxVyOaHOI9dW+DWF9bi6gziDOKNHhkT0jcSpRUnrVaQYUkv/asYaeQv8Nm+TT8l zOgON5fWNUWioe6htWlwKRuL1j9uBbGQaCIm7O4GkFu7sOOLEMhTYZ+cNQqHfEi3FI6S hDyw== X-Gm-Message-State: AOAM530pFBVyvWdPIRc6jy5LuaBg/7+hpaeo2+xbbJgYEWgxW6bkdmo3 GBYkmsbHuzyyzWJJF/kwQE7w2as3309LTisY0//uy8j8vO5N+x/V092tJc4TZ7FTtJBTOWmilhk FTq1G6Zus2C8= X-Received: by 2002:ac8:4d19:: with SMTP id w25mr323901qtv.175.1622147012418; Thu, 27 May 2021 13:23:32 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwzFops8/UrKEf5HfwY3iEbhr5r+2t8bpk0m5+pQMv9Qf3pzrX5D7bqd/iDokt9cv0Uh9qJDA== X-Received: by 2002:ac8:4d19:: with SMTP id w25mr323885qtv.175.1622147012142; Thu, 27 May 2021 13:23:32 -0700 (PDT) Received: from localhost.localdomain (bras-base-toroon474qw-grc-72-184-145-4-219.dsl.bell.ca. [184.145.4.219]) by smtp.gmail.com with ESMTPSA id t17sm1981378qto.92.2021.05.27.13.23.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 May 2021 13:23:31 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Mike Rapoport , peterx@redhat.com, Andrew Morton , Mike Kravetz , Jerome Glisse , Miaohe Lin , Nadav Amit , Hugh Dickins , Matthew Wilcox , Jason Gunthorpe , "Kirill A . Shutemov" , Andrea Arcangeli , Axel Rasmussen Subject: [PATCH v3 22/27] hugetlb/userfaultfd: Handle uffd-wp special pte in hugetlb pf handler Date: Thu, 27 May 2021 16:23:28 -0400 Message-Id: <20210527202328.32154-1-peterx@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210527201927.29586-1-peterx@redhat.com> References: <20210527201927.29586-1-peterx@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="US-ASCII" X-Rspamd-Queue-Id: 75293C00774F Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=NrjOfxut; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf14.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=peterx@redhat.com X-Rspamd-Server: rspam03 X-Stat-Signature: d71twztsfbmasx3hcuaxgw5pwkjyom4a X-HE-Tag: 1622147008-425252 Content-Transfer-Encoding: quoted-printable 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: Teach the hugetlb page fault code to understand uffd-wp special pte. For example, when seeing such a pte we need to convert any write fault into a= read one (which is fake - we'll retry the write later if so). Meanwhile, for handle_userfault() we'll need to make sure we must wait for the special s= wap pte too just like a none pte. Note that we also need to teach UFFDIO_COPY about this special pte across= the code path so that we can safely install a new page at this special pte as= long as we know it's a stall entry. Signed-off-by: Peter Xu --- fs/userfaultfd.c | 5 ++++- mm/hugetlb.c | 26 ++++++++++++++++++++------ mm/userfaultfd.c | 5 ++++- 3 files changed, 28 insertions(+), 8 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 15031d6f1f17..6ef7b56760bf 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -245,8 +245,11 @@ static inline bool userfaultfd_huge_must_wait(struct= userfaultfd_ctx *ctx, /* * Lockless access: we're in a wait_event so it's ok if it * changes under us. + * + * Regarding uffd-wp special case, please refer to comments in + * userfaultfd_must_wait(). */ - if (huge_pte_none(pte)) + if (huge_pte_none(pte) || pte_swp_uffd_wp_special(pte)) ret =3D true; if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) ret =3D true; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index c64dfd0a9883..a17d894312c0 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4707,7 +4707,8 @@ static inline vm_fault_t hugetlb_handle_userfault(s= truct vm_area_struct *vma, static vm_fault_t hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma, struct address_space *mapping, pgoff_t idx, - unsigned long address, pte_t *ptep, unsigned int flags) + unsigned long address, pte_t *ptep, + pte_t old_pte, unsigned int flags) { struct hstate *h =3D hstate_vma(vma); vm_fault_t ret =3D VM_FAULT_SIGBUS; @@ -4831,7 +4832,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct = *mm, =20 ptl =3D huge_pte_lock(h, mm, ptep); ret =3D 0; - if (!huge_pte_none(huge_ptep_get(ptep))) + if (!pte_same(huge_ptep_get(ptep), old_pte)) goto backout; =20 if (anon_rmap) { @@ -4841,6 +4842,12 @@ static vm_fault_t hugetlb_no_page(struct mm_struct= *mm, page_dup_rmap(page, true); new_pte =3D make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE) && (vma->vm_flags & VM_SHARED))); + /* + * If this pte was previously wr-protected, keep it wr-protected even + * if populated. + */ + if (unlikely(pte_swp_uffd_wp_special(old_pte))) + new_pte =3D huge_pte_wrprotect(huge_pte_mkuffd_wp(new_pte)); set_huge_pte_at(mm, haddr, ptep, new_pte); =20 hugetlb_count_add(pages_per_huge_page(h), mm); @@ -4956,8 +4963,13 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, str= uct vm_area_struct *vma, mutex_lock(&hugetlb_fault_mutex_table[hash]); =20 entry =3D huge_ptep_get(ptep); - if (huge_pte_none(entry)) { - ret =3D hugetlb_no_page(mm, vma, mapping, idx, address, ptep, flags); + /* + * uffd-wp-special should be handled merely the same as pte none + * because it's basically a none pte with a special marker + */ + if (huge_pte_none(entry) || pte_swp_uffd_wp_special(entry)) { + ret =3D hugetlb_no_page(mm, vma, mapping, idx, address, ptep, + entry, flags); goto out_mutex; } =20 @@ -5091,7 +5103,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_= mm, pgoff_t idx =3D vma_hugecache_offset(h, dst_vma, dst_addr); unsigned long size; int vm_shared =3D dst_vma->vm_flags & VM_SHARED; - pte_t _dst_pte; + pte_t _dst_pte, cur_pte; spinlock_t *ptl; int ret =3D -ENOMEM; struct page *page; @@ -5213,8 +5225,10 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst= _mm, if (idx >=3D size) goto out_release_unlock; =20 + cur_pte =3D huge_ptep_get(dst_pte); ret =3D -EEXIST; - if (!huge_pte_none(huge_ptep_get(dst_pte))) + /* Please refer to shmem_mfill_atomic_pte() for uffd-wp special case */ + if (!huge_pte_none(cur_pte) && !pte_swp_uffd_wp_special(cur_pte)) goto out_release_unlock; =20 if (vm_shared) { diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 82c235f555b8..af79f3d3a001 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -364,6 +364,8 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb= (struct mm_struct *dst_mm, } =20 while (src_addr < src_start + len) { + pte_t pteval; + BUG_ON(dst_addr >=3D dst_start + len); =20 /* @@ -386,8 +388,9 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb= (struct mm_struct *dst_mm, goto out_unlock; } =20 + pteval =3D huge_ptep_get(dst_pte); if (mode !=3D MCOPY_ATOMIC_CONTINUE && - !huge_pte_none(huge_ptep_get(dst_pte))) { + !huge_pte_none(pteval) && !pte_swp_uffd_wp_special(pteval)) { err =3D -EEXIST; mutex_unlock(&hugetlb_fault_mutex_table[hash]); i_mmap_unlock_read(mapping); --=20 2.31.1