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 X-Spam-Level: X-Spam-Status: No, score=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E81DC4363C for ; Wed, 7 Oct 2020 08:39:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB3EB2080A for ; Wed, 7 Oct 2020 08:39:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hx12AvDZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727909AbgJGIjO (ORCPT ); Wed, 7 Oct 2020 04:39:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:54840 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727832AbgJGIjO (ORCPT ); Wed, 7 Oct 2020 04:39:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602059951; 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=K7kkBLB4LmWktBQQQyJlNEIqp22tQV8Q0pHwxVqZhcA=; b=hx12AvDZDu1xQLTjxGuxkKCdoFaoVWlPklQekY1mmUlaCTm4FxxXdPW2WjZNbFQmfQO0FE jyNgtXc+8MjPPIAwg5yKw970jCALiO7b2g3eeW881jCLgERaIua0StN8CarioRgYU7/Rn3 zGSdbu2K00nCUvXjqPNoFeOptCJyRns= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-417-jHqr9XOfMkqnFVRZQU1K8A-1; Wed, 07 Oct 2020 04:39:08 -0400 X-MC-Unique: jHqr9XOfMkqnFVRZQU1K8A-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 09CD4803F5D; Wed, 7 Oct 2020 08:39:06 +0000 (UTC) Received: from [10.36.115.15] (ovpn-115-15.ams2.redhat.com [10.36.115.15]) by smtp.corp.redhat.com (Postfix) with ESMTP id 915F31002C2B; Wed, 7 Oct 2020 08:39:03 +0000 (UTC) Subject: Re: [PATCH] arm64/mm: Validate hotplug range before creating linear mapping To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: will@kernel.org, catalin.marinas@arm.com, Mark Rutland , Ard Biesheuvel , Steven Price , Robin Murphy , Andrew Morton , linux-kernel@vger.kernel.org, Michal Hocko References: <1600332402-30123-1-git-send-email-anshuman.khandual@arm.com> <7c39c046-b950-ea4c-fa4d-e0a5d6171147@redhat.com> <72ea7056-5289-3eb0-eca9-a8444524667e@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW 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/mWutNPt95w9wSsUyATLmtNrwccz63W5Ag0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAGJAjwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/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 GmbH Message-ID: <70a76220-9acd-06b6-e074-dc9cbb6668da@redhat.com> Date: Wed, 7 Oct 2020 10:39:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <72ea7056-5289-3eb0-eca9-a8444524667e@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> We do have __add_pages()->check_hotplug_memory_addressable() where we >> already check against MAX_PHYSMEM_BITS. > > Initially, I thought about check_hotplug_memory_addressable() but the > existing check that asserts end of hotplug wrt MAX_PHYSMEM_BITS, is > generic in nature. AFAIK the linear mapping problem is arm64 specific, > hence I was not sure whether to add an arch specific callback which > will give platform an opportunity to weigh in for these ranges. Also on s390x, the range where you can create an identity mapping depends on - early kernel setup - kasan (I assume it's the same for all archs) See arch/s390/mm/vmem.c:vmem_add_mapping(), which contains similar checks (VMEM_MAX_PHYS). > > But hold on, check_hotplug_memory_addressable() only gets called from > __add_pages() after linear mapping creation in arch_add_memory(). How > would it help ? We need some thing for add_memory(), its variants and > also possibly for memremap_pages() when it calls arch_add_memory(). > Good point. We chose that place for simplicity when adding it (I was favoring calling it at two places back then). Now, we might have good reason to move the checks further up the call chain. Most probably, struct range memhp_get_addressable_range(bool need_mapping) { ... } Would make sense, to deal with memremap_pages() without identity mappings. We have two options: 1. Generalize the checks, check early in applicable functions. Have a single way to get applicable ranges, both in callers, and inside the functions. 2. Keep the checks where they are. Add memhp_get_addressable_range() so callers can figure limits out. It's less clear what the relation between the different checks is. And it's likely if things change at one place that we miss the other place. >> struct range memhp_get_addressable_range(void) >> { >> const u64 max_phys = (1ull << (MAX_PHYSMEM_BITS + 1)) - 1; >> struct range range = arch_get_mappable_range(); > > What would you suggest as the default fallback range if a platform > does not define this callback. Just the largest possible range until we implement them. IIRC, an s390x version should be easy to add. > >> >> if (range.start > max_phys) { >> range.start = 0; >> range.end = 0; >> } >> range.end = max_t(u64, range.end, max_phys); > > min_t instead ? Yeah :) > >> >> return range; >> } >> >> >> That, we can use in check_hotplug_memory_addressable(), and also allow >> add_memory*() users to make use of it. > > So this check would happen twice during a hotplug ? Right now it's like calling a function with wrong arguments - you just don't have a clue what valid arguments are, because non-obvious errors (besides -ENOMEM, which is a temporary error) pop up deep down the call chain. For example, virito-mem would use it to detect during device initialization the usable device range, and warn the user accordingly. It currently manually checks for MAX_PHYSMEM_BITS, but that's just ugly. Failing at random add_memory() calls (permanently!) is not so nice. In case of DIMMs, we could use it to detect if adding parts of a DIMM won't work (and warn the user early). We could try to add as much as possible. -- Thanks, David / dhildenb