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[79.242.52.71]) by smtp.gmail.com with ESMTPSA id fb4-20020a05600c520400b00413e4ff2884sm3508154wmb.40.2024.03.13.15.03.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Mar 2024 15:03:05 -0700 (PDT) Message-ID: Date: Wed, 13 Mar 2024 23:03:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory: Fix missing pte marker for !page on pte zaps To: peterx@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , Muhammad Usama Anjum References: <20240313213107.235067-1-peterx@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20240313213107.235067-1-peterx@redhat.com> 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: 3D29840022 X-Rspam-User: X-Stat-Signature: x9wjpgqbeqdxgqbd55gkhmaxftt6y4ut X-Rspamd-Server: rspam01 X-HE-Tag: 1710367389-520717 X-HE-Meta: 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 6xsp1QwB yTQ4Ub8pZMSMtM+t15DxqIWP35nswRFPRoZDObKzP5Jt/VpRR4MegjgcY3aga6m3y/r6EBbeUVUxyv53Jgxh3MNesb1xdPHo0R0t20/Dunge/QU/GgVlOY0XJuwHFyVs9DiFQLivDZupl/eXVapHGT71CT2491GEyPZDwrkR0bWtZK438lOkLkQuV5MaoY3KCofSPs9rqmUmW6hk= 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: List-Subscribe: List-Unsubscribe: On 13.03.24 22:31, peterx@redhat.com wrote: > From: Peter Xu > > Commit 0cf18e839f64 of large folio zap work broke uffd-wp. Now mm's uffd > unit test "wp-unpopulated" will trigger this WARN_ON_ONCE(). Good that I added the WARN_ON_ONCE() :) > > The WARN_ON_ONCE() asserts that an VMA cannot be registered with > userfaultfd-wp if it contains a !normal page, but it's actually possible. > One example is an anonymous vma, register with uffd-wp, read anything will > install a zero page. Then when zap on it, this should trigger. Are you sure? zap_install_uffd_wp_if_needed() contains right at the start: /* Zap on anonymous always means dropping everything */ if (vma_is_anonymous(vma)) return; So if that's the case the unit test triggers, I'm confused. > > What's more, removing that WARN_ON_ONCE may not be enough either, because > we should also not rely on "whether it's a normal page" to decide whether > pte marker is needed. For example, one can register wr-protect over some > DAX regions to track writes when UFFD_FEATURE_WP_ASYNC enabled, in which > case it can have page==NULL for a devmap but we may want to keep the marker > around. I thought uffd-wp was limited to specific backends only. But looks like that changed with UFFD_FEATURE_WP_ASYNC, I guess? Change itself looks, good. Not sure about the anon_vma example above. Thanks! Acked-by: David Hildenbrand > > Cc: Muhammad Usama Anjum > Cc: David Hildenbrand > Fixes: 0cf18e839f64 ("mm/memory: handle !page case in zap_present_pte() separately") > Signed-off-by: Peter Xu > --- > mm/memory.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/memory.c b/mm/memory.c > index f2bc6dd15eb8..904f70b99498 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1536,7 +1536,9 @@ static inline int zap_present_ptes(struct mmu_gather *tlb, > ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); > arch_check_zapped_pte(vma, ptent); > tlb_remove_tlb_entry(tlb, pte, addr); > - VM_WARN_ON_ONCE(userfaultfd_wp(vma)); > + if (userfaultfd_pte_wp(vma, ptent)) > + zap_install_uffd_wp_if_needed(vma, addr, pte, 1, > + details, ptent); > ksm_might_unmap_zero_page(mm, ptent); > return 1; > } -- Cheers, David / dhildenb