From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8204E1D434D for ; Thu, 5 Dec 2024 08:10:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733386233; cv=none; b=YmWgZk7B3L7Dtaw88ybC8vcYQdEoLIeI07KCvgvvGYEddz5E6J9wEsCCCR8tHVUN9I4kd1US3gpiNxpwzGSFn8y+7v64bGF5oDY0Lk7dd6vKwaLTdv9+GOaiTlL2XEpG3XT3tOfL1T9bmYoDKwLl0VM4XZJnqCJUou1rJwbUrak= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733386233; c=relaxed/simple; bh=AaejfpshI/j70/aPnw+2SbHvzHsCIkJm51PRjqn5Dyw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SmuNxtuwVi5rnxkONDIEJc/qAoaH899JHT1G/xMr3gM+B/lP5F6G15xW/zXyd47d+s5Gb9COAk/ds71TANYKr/a8Ggh8n6M/5Ah4jfUuYdcp89lsypxYQmM88FTmvduD69Z7CeOUFqqgoXVuorLcdJBm2nRoHgW+VierYHqiFOc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ImKTlVUt; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ImKTlVUt" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1733386230; 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:autocrypt:autocrypt; bh=slMPncPUFapuW6Mvq7gRKO5PZvp1ywMT4KjtePW1i3U=; b=ImKTlVUtvTStCltBm/He+82wMzeI987xhm3wdeJSz+BOWBeVwu5VKNYJwmyojIkhbZB/jH 5ugaY5v0eb40Z+iLDpOzRR/17OonEsmEvdnmZUj6YD2BIeSk+Sn5jzbySelmjTTP9LNNq3 3b1pAgBPhKluhYhS0yzkxgLVagLzutc= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-363-8zG0O0RpO6234pV7d4KHjg-1; Thu, 05 Dec 2024 03:10:27 -0500 X-MC-Unique: 8zG0O0RpO6234pV7d4KHjg-1 X-Mimecast-MFC-AGG-ID: 8zG0O0RpO6234pV7d4KHjg Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4349cbf726cso3538265e9.3 for ; Thu, 05 Dec 2024 00:10:27 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1733386226; x=1733991026; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=slMPncPUFapuW6Mvq7gRKO5PZvp1ywMT4KjtePW1i3U=; b=U26ub2dqjwdaaRVrx/pHilfnwYwJR0//ZhYjJ2ThITBYGUACXbOs7LlmKW9G1dKqWJ BQRVG7/C7rIcly9YJRXXChd1VyDhlV2o9f5exE06pEj/l6AS7I8gX+YEiLDdWKsBpLKv nNdBRA3xgjoV1AEKSMgesqfUiZYZEeH7hJJVTuBwJJQApeTX+GMvn3gNFtXO5SncDA1O PRIBzLYt5ChgqhcHmIBqLaaA8aAEqjpcVgiMMXexNpg8h73IvbRy5GEp6vfYPFLE2nxD u/s0eiuZw+H9rWv1K3empc1tfjAi1/y2RlQjWHF+gq0vB0/xZQN74iDclhUIdU5h2Fg9 IihA== X-Forwarded-Encrypted: i=1; AJvYcCUCDq/11gVE2r/NahAcPlBxiQQjeT85kYnlmL3aaf93uFFq/eeUoTH17VUNfgVkXrc0jZ6XIHVg/1Dd@vger.kernel.org X-Gm-Message-State: AOJu0Yzr3tvRSf5XRqE3J9gKs7x7uFyi92HUO9jxHaZSqDsFBI9Nqd2A uIBS+lGtlUfgiMN9PKpA0KPufrTBuDbSFS4ld3gYPYq0wz1ZZfC215XBSvCQr0N55QHcw1CP3Iy uMdzmE1iLah6EY0foaphOunjK3z+y2WTxX8wYu9Jpq2ZApHMYaljq+R4ToP4= X-Gm-Gg: ASbGncveiyzVAlpFyCmpi/q3jVsAsjBhl+Oj/CTDr1hHMyx8A5sjIj/HGYhymdBA6vK +lRREu50FUuaLT7SlTycQioAAaIn3TmlXBX2o5/cfATBEnDCTIkq/eRXJSCS3cPHC3HKwJCxvMK V/w7No/KTAzIDWmrxTqqH/nzUChLjK8cwPdJv2fq1s3cmY5EYZniike3D4kn5ewhRIKfO84gamn 2LtMX0jtZoAx805wxW/ctswFgCKLvcsoPCraHhUfvc0QPK+JCFZdnhige4RXEqiTTYUA2fhyenv PI36Tlge/umliipC3xWhaOrtO9ErR3TjsaTjAlLwuazPAIAQt6svpsMR+jcPnn28zWAtn8qoMvs /1w== X-Received: by 2002:a05:600c:46cd:b0:434:882c:f746 with SMTP id 5b1f17b1804b1-434d09c8e42mr88417065e9.17.1733386226128; Thu, 05 Dec 2024 00:10:26 -0800 (PST) X-Google-Smtp-Source: AGHT+IFM15KEQ4HWgiUco48s1ntHOFiXjyp9MApGl4OaAdjqQ9MxyTsPbAhIx+LHO/GkpFZJSxqveg== X-Received: by 2002:a05:600c:46cd:b0:434:882c:f746 with SMTP id 5b1f17b1804b1-434d09c8e42mr88416835e9.17.1733386225729; Thu, 05 Dec 2024 00:10:25 -0800 (PST) Received: from ?IPV6:2003:cb:c70f:7e00:75dc:9c40:33fa:b5f8? (p200300cbc70f7e0075dc9c4033fab5f8.dip0.t-ipconnect.de. [2003:cb:c70f:7e00:75dc:9c40:33fa:b5f8]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-434d52c0cfdsm53188135e9.33.2024.12.05.00.10.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Dec 2024 00:10:24 -0800 (PST) Message-ID: <056a2305-db07-4168-868b-164493ff8587@redhat.com> Date: Thu, 5 Dec 2024 09:10:22 +0100 Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: avoid zeroing user movable page twice with init_on_alloc=1 To: Geert Uytterhoeven , Zi Yan Cc: Matthew Wilcox , Vlastimil Babka , linux-mm@kvack.org, Andrew Morton , Miaohe Lin , Kefeng Wang , John Hubbard , "Huang, Ying" , Ryan Roberts , Alexander Potapenko , Kees Cook , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org References: <20241011150304.709590-1-ziy@nvidia.com> <9942C08D-C188-461C-B731-F08DE294CD2B@nvidia.com> <09B2AB6A-B122-4287-B97E-F800E511097E@nvidia.com> <995E365D-5B83-41B3-A46C-6493D203A761@nvidia.com> From: David Hildenbrand Content-Language: en-US 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 05.12.24 09:04, Geert Uytterhoeven wrote: > Hi Zi, > > On Wed, Dec 4, 2024 at 7:30 PM Zi Yan wrote: >> On 4 Dec 2024, at 12:33, Zi Yan wrote: >>> On 4 Dec 2024, at 11:29, Matthew Wilcox wrote: >>>> On Wed, Dec 04, 2024 at 11:16:51AM -0500, Zi Yan wrote: >>>>>> So maybe the clearing done as part of page allocator isn't enough here. >>>>>> >>>>> Basically, mips needs to flush data cache if kmap address is aliased to >>>> >>>> People use "aliased" in contronym ways. Do you mean "has a >>>> non-congruent alias" or "has a congruent alias"? >>>> >>>>> userspace address. This means when mips has THP on, the patch below >>>>> is not enough to fix the issue. >>>>> >>>>> In post_alloc_hook(), it does not make sense to pass userspace address >>>>> in to determine whether to flush dcache or not. >>>>> >>>>> One way to fix it is to add something like arch_userpage_post_alloc() >>>>> to flush dcache if kmap address is aliased to userspace address. >>>>> But my questions are that >>>>> 1) if kmap address will always be the same for two separate kmap_local() calls, >>>> >>>> No. It just takes the next address in the stack. >>> >>> Hmm, if kmap_local() gives different addresses, wouldn’t init_on_alloc be >>> causing issues before my patch? In the page allocator, the page is zeroed >>> from one kmap address without flush, then clear_user_highpage() clears >>> it again with another kmap address with flush. After returning to userspace, >>> the user application works on the page but when the cache line used by >>> init_on_alloc is written back (with 0s) at eviction, user data is corrupted. >>> Am I missing anything? Or all arch with cache aliasing never enables >>> init_on_alloc? >> >> Hi Geert, >> >> Regarding the above concern, have you ever had CONFIG_INIT_ON_ALLOC_DEFAULT_ON >> for your MIPS machine and encountered any issue? Or let me know if my reasoning >> above is flawed. >> >> To test it, I wonder if you can 1) revert my patch and 2) turn on >> CONFIG_INIT_ON_ALLOC_DEFAULT_ON for your MIPS machine and run some applications >> to see if any error happens. > > That seems to work fine... > > Kernel log confirms it's enabled: > -mem auto-init: stack:off, heap alloc:off, heap free:off > +mem auto-init: stack:off, heap alloc:on, heap free:off If I'm not wrong that's expected ... because we'll be double-zeroing that memory, clearing the cache :) I guess the question is, how *effective* is CONFIG_INIT_ON_ALLOC_DEFAULT_ON on systems to prevent exposing un-zeroed data to userspace, when it doesn't end up doing the flush we really need. -- Cheers, David / dhildenb