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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 237E4C76188 for ; Wed, 5 Apr 2023 15:51:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7C6B96B0072; Wed, 5 Apr 2023 11:51:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7763E6B0074; Wed, 5 Apr 2023 11:51:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 63E4E6B0075; Wed, 5 Apr 2023 11:51:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 55A176B0072 for ; Wed, 5 Apr 2023 11:51:18 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 249FA1A0D26 for ; Wed, 5 Apr 2023 15:51:18 +0000 (UTC) X-FDA: 80647776636.24.731BE27 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf23.hostedemail.com (Postfix) with ESMTP id AE12C140011 for ; Wed, 5 Apr 2023 15:51:15 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=JIjze3aR; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf23.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1680709875; h=from:from:sender: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:dkim-signature; bh=zwcds+UtbfQIbiuF3/Xn2nxiwljEp+1pjIA6S8P9CNE=; b=e8qXrBkV4wJeBq9OtkFXuamjJUMxAv/nHGRo2gSdc6EEz66KGlb3CcVs31Egi6YiQ+rEUr m3CuEe+nySkbObQI35CfdX9hEfhvdtSv2NKgiOAO78rD7fQ6MSiEP/8E2ogtsiO6huIH/H h/z8/DFuCJH+hNNjAauzcY3wfbx33VU= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=JIjze3aR; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf23.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1680709875; a=rsa-sha256; cv=none; b=v8VmYLww6OdmGgJLGoNrwzShXZ/OsltqKBYal4mRrOtNNQ0J7ExaXjXRsIjoUS4Fr8jOF6 +PHQjXJOB7vpRzRWoYnRxX7SrQGvl99Jyzdyxmw6Rty6n3dRWZqOGxwGUmMbxNVAUIRdtS D9MPTB+lwzNPQkdQIEPv6yvJtGysasI= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680709875; 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=zwcds+UtbfQIbiuF3/Xn2nxiwljEp+1pjIA6S8P9CNE=; b=JIjze3aRO+x1WK50rC2z1wTducNGlS6MdNGP7eXHqkg1Yv9KweoqtsA/FBbedcS9P9JDSY uvxbs1OJKBA+NSJjM1DCZQ6bLd7SjT/n1Omhl74TeRg+sJrFKnPYJ8DAstJgFNEXQvBLWW 6CrAH2Tw0wCZrC7+8K9li19M5pmJ7PM= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-313-kFvf7HkwOB-Bc8466T1znA-1; Wed, 05 Apr 2023 11:51:13 -0400 X-MC-Unique: kFvf7HkwOB-Bc8466T1znA-1 Received: by mail-wr1-f71.google.com with SMTP id v30-20020adfa1de000000b002d557ec6d15so4510302wrv.18 for ; Wed, 05 Apr 2023 08:51:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680709871; h=content-transfer-encoding:in-reply-to:organization:from:references :cc:to:content-language:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=zwcds+UtbfQIbiuF3/Xn2nxiwljEp+1pjIA6S8P9CNE=; b=4Q86KWVTsMGhwY3Kta8HgAfV6Zyv4z6MAFYT6arRB8li+XcAsAJtILbuqA7MraojO/ 83M8599cYfJmsM7Lv7yon1YO4QaiaDWHrUJnrJAMKvHrnLZ2mQUvqLJp7Kp3tmywdLGh CPpPoa/gMmBbiTjSE/pbyblobTU3X5+D5asdIWfrUhCUV4B/hbnjXEhXqZxtqiH6gMkx 5Jso5mnW9aQlH1cRNycli/rI3gUDm6gTEXUZ1uq6AzN54qUfH2Kc9dF270VDEaKP29Bl oFpvtrv4GGQXiGqy+fvsT8BQ2XbaePdC4vGOkVMnjetCiM9ssBrsys1wwOWnrhU4fjeN g4WA== X-Gm-Message-State: AAQBX9c8+StAS1g5SiMGq4WK6yEkaykSCdYNxehGxXtxn9DXXOHYUo6K UFcZqiURHlXP2+GTslWTsjltDahCRIxt6SHRaLwMCP3+VgebMxWZhduJOZOVn0oHIGAMlqWrxiN tCkHBXJg0MvM= X-Received: by 2002:a5d:460c:0:b0:2cf:feac:1ba4 with SMTP id t12-20020a5d460c000000b002cffeac1ba4mr4489146wrq.52.1680709871735; Wed, 05 Apr 2023 08:51:11 -0700 (PDT) X-Google-Smtp-Source: AKy350Z0Kdl7KzMunNzgacqXrtbvhCmqrBwFwQ712057u2CU5aKnkMXlHhzmgE+1a984DLcJhQUu6w== X-Received: by 2002:a5d:460c:0:b0:2cf:feac:1ba4 with SMTP id t12-20020a5d460c000000b002cffeac1ba4mr4489129wrq.52.1680709871360; Wed, 05 Apr 2023 08:51:11 -0700 (PDT) Received: from ?IPV6:2003:cb:c703:d00:ca74:d9ea:11e0:dfb? (p200300cbc7030d00ca74d9ea11e00dfb.dip0.t-ipconnect.de. [2003:cb:c703:d00:ca74:d9ea:11e0:dfb]) by smtp.gmail.com with ESMTPSA id x9-20020a5d4449000000b002e40d124460sm15350496wrr.97.2023.04.05.08.51.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Apr 2023 08:51:10 -0700 (PDT) Message-ID: <062cd239-179b-d146-8f5d-735e672b3237@redhat.com> Date: Wed, 5 Apr 2023 17:51:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [PATCH v1 1/2] mm/userfaultfd: fix uffd-wp handling for THP migration entries To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Muhammad Usama Anjum , stable@vger.kernel.org References: <20230405142535.493854-1-david@redhat.com> <20230405142535.493854-2-david@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: AE12C140011 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: 1rmdb54o9hxy6tnyh4qj6mktdujxymie X-HE-Tag: 1680709875-139412 X-HE-Meta: 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 Odr2oo0s syDAC6VcLlPQZrFwsMkf6wEfOiuOO/M+FohhmATdLht0hitnDoEAVOjAn/sW71k+Qmt7okxTM9bgvIGcaIm+m++yeqzr7kCMBVHyhJDPLfsZCG2rzqO9TkhmkD0P8L0aRVEzKFxNwQ5i66EljNx7TQ+HX5X4hwsqy26geFIWW+BzDYsN+2BeUkB//O0EQ7LnSixPN/Um4Gb+JqFnysnwxnkwyMBDSqooM/ImObE70hLJo1PNJyvaAO2/dYJSgkrHU/dVVOteA/j4jQvvtu5Q0O+DxHqzzUiq1Kdp+YMs5jwZkNhc21ibzXylsrbZtc41PGHDN3BGC/Kyphg8iNWpGb+T/s34uBghoZw7fjHDLqBO8+ZV5wGx6KGgYDc22tnnIn46OZ2S+txKJywmlUwTBcW1etsbOQp0IRoHNVkvfiuyFpbnHN5hE6qF/rNd67sPm5Lg85xL/nlxS0dFFQ2CFdjAQU1TAQpRwjHXT 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: On 05.04.23 17:43, Peter Xu wrote: > On Wed, Apr 05, 2023 at 05:17:31PM +0200, David Hildenbrand wrote: >> On 05.04.23 17:12, Peter Xu wrote: >>> On Wed, Apr 05, 2023 at 04:25:34PM +0200, David Hildenbrand wrote: >>>> Looks like what we fixed for hugetlb in commit 44f86392bdd1 ("mm/hugetlb: >>>> fix uffd-wp handling for migration entries in hugetlb_change_protection()") >>>> similarly applies to THP. >>>> >>>> Setting/clearing uffd-wp on THP migration entries is not implemented >>>> properly. Further, while removing migration PMDs considers the uffd-wp >>>> bit, inserting migration PMDs does not consider the uffd-wp bit. >>>> >>>> We have to set/clear independently of the migration entry type in >>>> change_huge_pmd() and properly copy the uffd-wp bit in >>>> set_pmd_migration_entry(). >>>> >>>> Verified using a simple reproducer that triggers migration of a THP, that >>>> the set_pmd_migration_entry() no longer loses the uffd-wp bit. >>>> >>>> Fixes: f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration") >>>> Cc: stable@vger.kernel.org >>>> Signed-off-by: David Hildenbrand >>> >>> Reviewed-by: Peter Xu >>> >>> Thanks, one trivial nitpick: >>> >>>> --- >>>> mm/huge_memory.c | 14 ++++++++++++-- >>>> 1 file changed, 12 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>> index 032fb0ef9cd1..bdda4f426d58 100644 >>>> --- a/mm/huge_memory.c >>>> +++ b/mm/huge_memory.c >>>> @@ -1838,10 +1838,10 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, >>>> if (is_swap_pmd(*pmd)) { >>>> swp_entry_t entry = pmd_to_swp_entry(*pmd); >>>> struct page *page = pfn_swap_entry_to_page(entry); >>>> + pmd_t newpmd; >>>> VM_BUG_ON(!is_pmd_migration_entry(*pmd)); >>>> if (is_writable_migration_entry(entry)) { >>>> - pmd_t newpmd; >>>> /* >>>> * A protection check is difficult so >>>> * just be safe and disable write >>>> @@ -1855,8 +1855,16 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, >>>> newpmd = pmd_swp_mksoft_dirty(newpmd); >>>> if (pmd_swp_uffd_wp(*pmd)) >>>> newpmd = pmd_swp_mkuffd_wp(newpmd); >>>> - set_pmd_at(mm, addr, pmd, newpmd); >>>> + } else { >>>> + newpmd = *pmd; >>>> } >>>> + >>>> + if (uffd_wp) >>>> + newpmd = pmd_swp_mkuffd_wp(newpmd); >>>> + else if (uffd_wp_resolve) >>>> + newpmd = pmd_swp_clear_uffd_wp(newpmd); >>>> + if (!pmd_same(*pmd, newpmd)) >>>> + set_pmd_at(mm, addr, pmd, newpmd); >>>> goto unlock; >>>> } >>>> #endif >>>> @@ -3251,6 +3259,8 @@ int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, >>>> pmdswp = swp_entry_to_pmd(entry); >>>> if (pmd_soft_dirty(pmdval)) >>>> pmdswp = pmd_swp_mksoft_dirty(pmdswp); >>>> + if (pmd_swp_uffd_wp(*pvmw->pmd)) >>>> + pmdswp = pmd_swp_mkuffd_wp(pmdswp); >>> >>> I think it's fine to use *pmd, but maybe still better to use pmdval? I >>> worry pmdp_invalidate()) can be something else in the future that may >>> affect the bit. >> >> Wondering how I ended up with that, I realized that it's actually >> wrong and might have worked by chance for my reproducer on x86. >> >> That should make it work: >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index f977c965fdad..fffc953fa6ea 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -3257,7 +3257,7 @@ int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, >> pmdswp = swp_entry_to_pmd(entry); >> if (pmd_soft_dirty(pmdval)) >> pmdswp = pmd_swp_mksoft_dirty(pmdswp); >> - if (pmd_swp_uffd_wp(*pvmw->pmd)) >> + if (pmd_uffd_wp(pmdval)) >> pmdswp = pmd_swp_mkuffd_wp(pmdswp); >> set_pmd_at(mm, address, pvmw->pmd, pmdswp); >> page_remove_rmap(page, vma, true); > > I guess pmd_swp_uffd_wp() just reads the _USER bit 2 which is also set for > a present pte, but then it sets swp uffd-wp always even if it was not set. > Yes. I modified the reproducer to migrate without uffd-wp first and we suddenly gain a uffd-wp bit. > Yes the change must be squashed in to be correct, with that, my R-b keeps. Thanks, I will resend later. -- Thanks, David / dhildenb