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 724D5C4829A for ; Tue, 13 Feb 2024 13:22:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DE4838D0011; Tue, 13 Feb 2024 08:22:55 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D95378D0001; Tue, 13 Feb 2024 08:22:55 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BBF9F8D0011; Tue, 13 Feb 2024 08:22:55 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id AA0D48D0001 for ; Tue, 13 Feb 2024 08:22:55 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 4ABA91A0BB6 for ; Tue, 13 Feb 2024 13:22:55 +0000 (UTC) X-FDA: 81786845910.30.3BC72D7 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf23.hostedemail.com (Postfix) with ESMTP id 268CA14001E for ; Tue, 13 Feb 2024 13:22:52 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=buZCaCnc; spf=pass (imf23.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707830573; 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=VEC2sf7LFQqJw89DqYMmjZDJRFTDZsCnAL9w8HwRw84=; b=Qf4YjiJSk69lIqPR9fYtIlzI7MP63NrkAtyPApDVtytAxs70BgLCPHVxCm+lFer70ImG2Q W/gWkt/ZKsVp7Y/nEYj93qFgxm6/HpEBGnUbi9LkXGMNMYqQzr5dwjzo+HSAleYHt2ZTlz ns+m6ooIh8TMqJA7H6PteXlxkYh4Se8= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=buZCaCnc; spf=pass (imf23.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707830573; a=rsa-sha256; cv=none; b=x7eEZfGis+7XgkLcLzsZwCTf1rCO+N8xZUpgKoPsn4NgIDUugWBdKblOJP9ABpKFgN3a0q VBY1gC0wGqaF1C4vZ2PNLk8gUtisuFfUcVuvPw1ZhQ5vC13bslzva19qWnj8HCYlyhu+74 AO776DleAtxulqf3mpb2ycSb6J+ksDc= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1707830572; 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=VEC2sf7LFQqJw89DqYMmjZDJRFTDZsCnAL9w8HwRw84=; b=buZCaCncE1nWQqrCYuGoDXErTsRc3eU8kJBTcv7fH7AmtQGNqNrBfH5jXxjekVRqr/Ac+q Dkiqi6ED7vv15swNDdNALp84kwq+2rMsevnuazxEFDgw4BC0dOQeT0jLfDhJXL5OzUhhGb l/flfYZAXA97S2DpEvZyIjX7cEvzZC8= 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-640-nj2bTYnQMduM4dSvR9jVJA-1; Tue, 13 Feb 2024 08:22:50 -0500 X-MC-Unique: nj2bTYnQMduM4dSvR9jVJA-1 Received: by mail-wr1-f71.google.com with SMTP id ffacd0b85a97d-33cd1a98261so425761f8f.0 for ; Tue, 13 Feb 2024 05:22:50 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707830569; x=1708435369; 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=VEC2sf7LFQqJw89DqYMmjZDJRFTDZsCnAL9w8HwRw84=; b=Bh/O9fBRx7V1otI4Iinu0Y+S+x2xc4Zc9R7waoYvE8M8F5AWWnGxVqAeLvZk05WjEJ hbg1nXt5VU3LKPxI8ycxjI0iVPN0Z6XXrh8eGu7RSgeisJCUqQQZQAxpfgtHmBkbadR+ KZiJooK7A67jEljPwacwReiaRDTE7scf7Qtf5BjhdAoSSNXmtbRNom00nTk2suiSngeN HpTV4XGZG+6iS+6DmRzQSZgcswiFogvV0dr97yJu7yfmU4QS12jA3NDRY2/xYwOzx7hN I105hTrbTWtbTOxhAHVh0jUUjPzjoLW87J4rU1vrOC/LwuEl+WN437lxr5ePOZp/L6aP 6t/A== X-Forwarded-Encrypted: i=1; AJvYcCUd3Fpi0kdhPLOgm4aD2httXB+mzpPArS6cbPJXQmCnmdwAzyq9xKkBfsWyYCNan2eTCuqO0MK3niaFhe6FekUm8TE= X-Gm-Message-State: AOJu0Yx8rd7w3dizp3w/Os0G+th0SYTOCzUtMcrQ7PtQvbTRK8vRQSro uvc0kj/T6xxob+i9KJMiww06/JYWxP9uU7p8pmt71EYIY6M1LUIQu2PaAf65X5LDj4rXKXlRhKX k2M4cVbdTjTYAU2l8RE8x/JBNhQ6C4qTTCQUKI0hw80upcplp X-Received: by 2002:a05:6000:10c6:b0:33b:66c2:9735 with SMTP id b6-20020a05600010c600b0033b66c29735mr8069223wrx.18.1707830569489; Tue, 13 Feb 2024 05:22:49 -0800 (PST) X-Google-Smtp-Source: AGHT+IGL/PyU78LN2pLyFDTojnXty/hEr//ZGxzu7Mnoxcl1sF1xcoNhwzPxA9NHcxk55spVgHsUig== X-Received: by 2002:a05:6000:10c6:b0:33b:66c2:9735 with SMTP id b6-20020a05600010c600b0033b66c29735mr8069187wrx.18.1707830569065; Tue, 13 Feb 2024 05:22:49 -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 m18-20020a5d56d2000000b0033b60bad2fcsm9482744wrw.113.2024.02.13.05.22.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Feb 2024 05:22:48 -0800 (PST) Message-ID: Date: Tue, 13 Feb 2024 14:22:46 +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> <99e2a92c-f2a2-4e1e-8ce2-08caae2cb7e4@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: 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: 268CA14001E X-Rspam-User: X-Stat-Signature: nyfqgua44rfwayyimnmuwjoiu4ga7je3 X-Rspamd-Server: rspam01 X-HE-Tag: 1707830572-439030 X-HE-Meta: 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 9cEuBF2c EUkBvvQgD8DRsgtsWonPcdqdWx4mdurQtQn/oDMFTa+5g5WJ+44puDM8sOGhkpdQ2wqJcHhT9aK3/nH3EPDZGdTJbivmF49QUxT2tMVm9CYbNvFUQQrU5SIPkivNESl1KTrsJkLNfqEQiBQ+FMbkjqokGFdOvwX4oX9kcu4OV/R1Z7lOgdp5M1lSPYuMQC00NSFTv0f9vthiIs4PouixIgkIHUCp3SdipYXKydDyCUrHh9WV5IPzhbLUfiObgeq6Sl/8Tph1Yvh4nWJc+96KFkdiSBU/S1mny28jQ 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 14:20, Ryan Roberts wrote: > On 13/02/2024 13:13, David Hildenbrand wrote: >> 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) >>  { >> >> > > That would definitely work, but in that case, I might as well just check for it > in mm_is_user() (and personally I would change the name to mm_is_efi()): > > > static inline bool mm_is_user(struct mm_struct *mm) > { > return mm != &init_mm && !mm_is_efi(mm); > } > > Any objections? > Nope :) Maybe slap in an "unlikely()", because efi_mm *is* unlikely to show up. -- Cheers, David / dhildenb