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 4D4A1C4829A for ; Tue, 13 Feb 2024 13:13:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C59988D000F; Tue, 13 Feb 2024 08:13:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C08558D0001; Tue, 13 Feb 2024 08:13:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A34488D000F; Tue, 13 Feb 2024 08:13:35 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 8FDB98D0001 for ; Tue, 13 Feb 2024 08:13:35 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 402AE1C1042 for ; Tue, 13 Feb 2024 13:13:35 +0000 (UTC) X-FDA: 81786822390.16.9548EB9 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf09.hostedemail.com (Postfix) with ESMTP id 9C073140005 for ; Tue, 13 Feb 2024 13:13:32 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=BxAJQrnm; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.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=1707830012; 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=1kFF1ykf7ZVkdBjo0Btu3TmyP4G76fID/w0N/BNwg7k=; b=EVG6Ur3mNWfZ1P/8kc/DO9MmN13xXTotK8clgNWM9t+mS/+cyXmgNbeDGLodLtZo/7sfLS 3iq8oI8SRG2MgxsJB6CtIIvLPFyjM79S9O7R65aSMJMLQgu/3agrOjeaMwSnguJCWQ4s+C uHxdpg5vAMCl2WgUpbnEg5ugBlAaAlI= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=BxAJQrnm; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.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=1707830012; a=rsa-sha256; cv=none; b=A+x4EFGEDEzbbcax84e+hAd1ok/95dkiWAGX4xXrIBdY2Kv8MJUB0gBqgeW/niYaVBqthU WOYWwA5O4Qsn5i8klRAcK6p6UwZIJkL71C9y/q4v9/M+l/wX+jHR4piHrHRUnyyidAd2/4 KPw/rSBfOBcJwL3FA9UcwvY/EUG4Q70= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1707830011; 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=1kFF1ykf7ZVkdBjo0Btu3TmyP4G76fID/w0N/BNwg7k=; b=BxAJQrnm3UCEGn10Z3uvbX9ovHi2eIgyzknMFmrfrhyZmYewdWUjd3BdC4S3A6I+l07rR9 YsBZgBaszjwWRFjQOW9SHm0llDRG9Ht5/N4fkk0JibHaz04711RjAULkbxkpLBK4F1Ntaf vAt2KV4hf+mnPkdx0sMDvnFmHHo/uUE= 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-547-fFSjpmOaMhu1HnA7Gxw-cw-1; Tue, 13 Feb 2024 08:13:30 -0500 X-MC-Unique: fFSjpmOaMhu1HnA7Gxw-cw-1 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-40e53200380so27215745e9.3 for ; Tue, 13 Feb 2024 05:13:30 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707830009; x=1708434809; h=content-transfer-encoding:in-reply-to:organization:autocrypt: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=1kFF1ykf7ZVkdBjo0Btu3TmyP4G76fID/w0N/BNwg7k=; b=B3t/qDWpRQ7AqQDZan0jc5S9TqYuSrIcKNc7bCo8A8UyGLqozwfjg63fJYx+9ce+WB ZnlyIuo8Z9MBOHsSYKQ++pdOO41xfZpr8uxOJECQ/aADHovYwi8FjAq7+PVVsQ9Qqho9 1dMbwx688Kg8PnosFBmzFD+ZZ21T7e59sZewExUvuRNGie6ZqBvhnGCqrIv9I2UwvwyT KsrdSPt4FjC8m4gPmTwMhctItT2EDpuTAb5GSpzo4uMvLowhw6QPWken5RmtE71dHb7A airiFvLCh1bbLKVOCzXyIT/VMUjDx2n+eoJy3gBR2aXPx2t1pWv4Tvv8fGWugsYLrojy amCA== X-Gm-Message-State: AOJu0YyzVjOAVMp2XROYcXKPT4jH7OkguHuqRzITVptfoXVp3HGcwOqp JeLv3JK68xepUMFRI5Qkw7fb8wmrI5dH5zNzdQHivbrx9PJmdfPGg0Znou3moaL3yBTqYZSR2G9 trj4bul6OIJGZvWJBjCjw97H3je+S92H1+KELZ2FRhLOrLurt X-Received: by 2002:a05:600c:4ed3:b0:410:6a8b:6937 with SMTP id g19-20020a05600c4ed300b004106a8b6937mr8292048wmq.37.1707830009329; Tue, 13 Feb 2024 05:13:29 -0800 (PST) X-Google-Smtp-Source: AGHT+IFedhg4WC2rucFpz+Xs+0+uKCKsXMaUYqZP1r94vDN7x2OvlGAfvuWQNxb8q066f90YBcu2iw== X-Received: by 2002:a05:600c:4ed3:b0:410:6a8b:6937 with SMTP id g19-20020a05600c4ed300b004106a8b6937mr8291998wmq.37.1707830008909; Tue, 13 Feb 2024 05:13:28 -0800 (PST) X-Forwarded-Encrypted: i=1; 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 Received: from ?IPV6:2003:cb:c70a:4d00:b968:9e7a:af8b:adf7? (p200300cbc70a4d00b9689e7aaf8badf7.dip0.t-ipconnect.de. [2003:cb:c70a:4d00:b968:9e7a:af8b:adf7]) by smtp.gmail.com with ESMTPSA id q18-20020a7bce92000000b00410c04e5455sm7165370wmj.20.2024.02.13.05.13.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Feb 2024 05:13:28 -0800 (PST) Message-ID: <99e2a92c-f2a2-4e1e-8ce2-08caae2cb7e4@redhat.com> Date: Tue, 13 Feb 2024 14:13:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 19/25] arm64/mm: Wire up PTE_CONT for user mappings To: Ryan Roberts , Mark Rutland Cc: Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , James Morse , Andrey Ryabinin , Andrew Morton , Matthew Wilcox , Kefeng Wang , John Hubbard , Zi Yan , Barry Song <21cnbao@gmail.com>, Alistair Popple , Yang Shi , Nicholas Piggin , Christophe Leroy , "Aneesh Kumar K.V" , "Naveen N. Rao" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240202080756.1453939-1-ryan.roberts@arm.com> <20240202080756.1453939-20-ryan.roberts@arm.com> <64395ae4-3a7d-45dd-8f1d-ea6b232829c5@arm.com> <41499621-482f-455b-9f68-b43ea8052557@redhat.com> <1d302d7a-50ab-4ab4-b049-75ed4a71a87d@arm.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: <1d302d7a-50ab-4ab4-b049-75ed4a71a87d@arm.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: 8bit X-Rspamd-Queue-Id: 9C073140005 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: pn9ug8bfxmagpuar1jsp7j4igfisp66p X-HE-Tag: 1707830012-412036 X-HE-Meta: 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 T3qIZDe7 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 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 13.02.24 14:06, Ryan Roberts wrote: > On 13/02/2024 12:19, David Hildenbrand wrote: >> On 13.02.24 13:06, Ryan Roberts wrote: >>> On 12/02/2024 20:38, Ryan Roberts wrote: >>>> [...] >>>> >>>>>>>> +static inline bool mm_is_user(struct mm_struct *mm) >>>>>>>> +{ >>>>>>>> +    /* >>>>>>>> +     * Don't attempt to apply the contig bit to kernel mappings, because >>>>>>>> +     * dynamically adding/removing the contig bit can cause page faults. >>>>>>>> +     * These racing faults are ok for user space, since they get serialized >>>>>>>> +     * on the PTL. But kernel mappings can't tolerate faults. >>>>>>>> +     */ >>>>>>>> +    return mm != &init_mm; >>>>>>>> +} >>>>>>> >>>>>>> We also have the efi_mm as a non-user mm, though I don't think we manipulate >>>>>>> that while it is live, and I'm not sure if that needs any special handling. >>>>>> >>>>>> Well we never need this function in the hot (order-0 folio) path, so I think I >>>>>> could add a check for efi_mm here with performance implication. It's probably >>>>>> safest to explicitly exclude it? What do you think? >>>>> >>>>> Oops: This should have read "I think I could add a check for efi_mm here >>>>> *without* performance implication" >>>> >>>> It turns out that efi_mm is only defined when CONFIG_EFI is enabled. I can do >>>> this: >>>> >>>> return mm != &init_mm && (!IS_ENABLED(CONFIG_EFI) || mm != &efi_mm); >>>> >>>> Is that acceptable? This is my preference, but nothing else outside of efi >>>> references this symbol currently. >>>> >>>> Or perhaps I can convince myself that its safe to treat efi_mm like userspace. >>>> There are a couple of things that need to be garanteed for it to be safe: >>>> >>>>    - The PFNs of present ptes either need to have an associated struct page or >>>>      need to have the PTE_SPECIAL bit set (either pte_mkspecial() or >>>>      pte_mkdevmap()) >>>> >>>>    - Live mappings must either be static (no changes that could cause >>>> fold/unfold >>>>      while live) or the system must be able to tolerate a temporary fault >>>> >>>> Mark suggests efi_mm is not manipulated while live, so that meets the latter >>>> requirement, but I'm not sure about the former? >>> >>> I've gone through all the efi code, and conclude that, as Mark suggests, the >>> mappings are indeed static. And additionally, the ptes are populated using only >>> the _private_ ptep API, so there is no issue here. As just discussed with Mark, >>> my prefereence is to not make any changes to code, and just add a comment >>> describing why efi_mm is safe. >>> >>> Details: >>> >>> * Registered with ptdump >>>      * ptep_get_lockless() >>> * efi_create_mapping -> create_pgd_mapping … -> init_pte: >>>      * __ptep_get() >>>      * __set_pte() >>> * efi_memattr_apply_permissions -> efi_set_mapping_permissions … -> >>> set_permissions >>>      * __ptep_get() >>>      * __set_pte() >> >> Sound good. We could add some VM_WARN_ON if we ever get the efi_mm via the >> "official" APIs. > > We could, but that would lead to the same linkage issue, which I'm trying to > avoid in the first place: > > VM_WARN_ON(IS_ENABLED(CONFIG_EFI) && mm == efi_mm); > > This creates new source code dependencies, which I would rather avoid if possible. Just a thought, you could have a is_efi_mm() function that abstracts all that. diff --git a/include/linux/efi.h b/include/linux/efi.h index c74f47711f0b..152f5fa66a2a 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -692,6 +692,15 @@ extern struct efi { extern struct mm_struct efi_mm; +static inline void is_efi_mm(struct mm_struct *mm) +{ +#ifdef CONFIG_EFI + return mm == &efi_mm; +#else + return false; +#endif +} + static inline int efi_guidcmp (efi_guid_t left, efi_guid_t right) { -- Cheers, David / dhildenb