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 ACFA4D63954 for ; Wed, 20 Nov 2024 14:39:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2634A6B0089; Wed, 20 Nov 2024 09:39:39 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1ED4F6B008A; Wed, 20 Nov 2024 09:39:39 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 065D56B0092; Wed, 20 Nov 2024 09:39:38 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id D96366B0089 for ; Wed, 20 Nov 2024 09:39:38 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 5E213A0D37 for ; Wed, 20 Nov 2024 14:39:38 +0000 (UTC) X-FDA: 82806730398.10.8F466AB Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf08.hostedemail.com (Postfix) with ESMTP id 7B390160003 for ; Wed, 20 Nov 2024 14:39:01 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=RgQlzbgH; spf=pass (imf08.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=1732113330; 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=h3VNC3b6pyuHC0GRlERPYXF58+ZikMBaiQzrtXGN3kc=; b=gTwzH6d+v5iPARdJ5eyLL5au1Xf8Oe+N213DtPVTRbCdQLOfJw33UUvYP4d/h/+1kJnj4z 0KFyf3ZW2A4oxhk5fUnkYHUyercivqAQyYDn/qDaG+OOgYW4Ecob1he7TC8xkqnwP8vvPQ DEjlqQh9i4AZQ1+LyDKT77+dWjdzoac= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=RgQlzbgH; spf=pass (imf08.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=1732113330; a=rsa-sha256; cv=none; b=gaqwRsX0WRnRDo+5oayaQ5VxqKt7IhcCmBNmhrlWUoi4x97pbYTDEfoM03qup45kiB02vu 3M4XJQY4f1XIUMHKk/zqimcuOmMwUPo7S8xa6UCEI2gs4yHLFcfvC7RGv6ncogP4TM6wAu 2omVqwXoPhMTFI5pU2b4mhgW06izuOg= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1732113575; 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=h3VNC3b6pyuHC0GRlERPYXF58+ZikMBaiQzrtXGN3kc=; b=RgQlzbgHTUBP5Jw4rWEGtydMmx7E09dm7pxT/S1Bshb37C3wZSd3kRT6Lp8KF3C/+3WX6B F1xALe1cPvxonFDC1+34664GMdLQbD8O0mKWmb0njAOWN1U7r3Xn5xY5nW1i/mHE3mVeCW LXcXg+C2DUkvEGzm5A5Cpk5WvPe2Ezo= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-600-ZZQ0Aa8qOgOjKZZyfa-60g-1; Wed, 20 Nov 2024 09:39:31 -0500 X-MC-Unique: ZZQ0Aa8qOgOjKZZyfa-60g-1 X-Mimecast-MFC-AGG-ID: ZZQ0Aa8qOgOjKZZyfa-60g Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-38236ca50d5so1946625f8f.0 for ; Wed, 20 Nov 2024 06:39:31 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1732113570; x=1732718370; 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=h3VNC3b6pyuHC0GRlERPYXF58+ZikMBaiQzrtXGN3kc=; b=dJv8c5MDzP3cUSjp3MTZvrjf1Cco2AY7ey3HQpH5gDVvZk9Lq4ULeehFf5AmodBMiL BXY6TO6m0mxKuvrX5wThsdgo1ZTWsa19ZrndJuOnizeRGOoSb+cILWMTW9Ihsyjp4c2N np4xyUxFT8o43InfBtz8rV4yoq7LnhKIOHy65qfut/5ApUWu/Cp8gWDGA6UNYpmAy27z /Ww+92CC/1Icb4YRrXvesInpyqr9fE7q8U72oCaa4hRwuk80dprcSIA+at3mmN2OiHPI jMyL+TZ91rGON9FYUWu7oqH5rSMoFVrYibP1iXiMi7BaTSF78cWGjQmlZKkiy18ilsNR WgFg== X-Forwarded-Encrypted: i=1; AJvYcCWpZD/diNDZWVe4QdGrpi6suTOfhVDFE0UHG78CErphyKTq0UgaeiHFMsolTPpPeC5rZoExUPv6Nw==@kvack.org X-Gm-Message-State: AOJu0Yy9bsnyWrZgSg87rmHqlLCeiCZ7BmtEkdTpPwhWfI5zpmG2TsPc g8UggpLYyYiXpytBOSJOjbXXeRSurVIVgQScd1yRGPIZiPl8J47ZDo7VjgNinjTQEX4w5W1ztmc UGbINNx+lRguKKmsQzWZFtVKjmvcfkkQBFapb4WAcN8KUQMW2 X-Received: by 2002:a05:6000:2d01:b0:382:5284:995 with SMTP id ffacd0b85a97d-38254af52edmr1741464f8f.16.1732113570637; Wed, 20 Nov 2024 06:39:30 -0800 (PST) X-Google-Smtp-Source: AGHT+IF3PCfqnU0zEBWkF3nAGnG0ftAq5fWrullBMMZxuX6xEoDVnbaIbozVyZf2Yd0u6zKlmX8E6w== X-Received: by 2002:a05:6000:2d01:b0:382:5284:995 with SMTP id ffacd0b85a97d-38254af52edmr1741442f8f.16.1732113570280; Wed, 20 Nov 2024 06:39:30 -0800 (PST) Received: from ?IPV6:2003:cb:c705:4200:ce79:acf6:d832:60df? (p200300cbc7054200ce79acf6d83260df.dip0.t-ipconnect.de. [2003:cb:c705:4200:ce79:acf6:d832:60df]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-433b45d4c68sm21058255e9.22.2024.11.20.06.39.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Nov 2024 06:39:29 -0800 (PST) Message-ID: <3ed18ba1-e4b1-461e-a3a7-5de2df59ca60@redhat.com> Date: Wed, 20 Nov 2024 15:39:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 07/11] fs/proc/vmcore: introduce PROC_VMCORE_DEVICE_RAM to detect device RAM ranges in 2nd kernel To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, virtualization@lists.linux.dev, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, kexec@lists.infradead.org, Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Vivek Goyal , Dave Young , Thomas Huth , Cornelia Huck , Janosch Frank , Claudio Imbrenda , Eric Farman , Andrew Morton References: <20241025151134.1275575-1-david@redhat.com> <20241025151134.1275575-8-david@redhat.com> <4b07a3eb-aad6-4436-9591-289c6504bb92@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-MFC-PROC-ID: DhMIM_Ay7eY0Pm27QTfS1rvI9sSDC2VblMIRpZqfPHc_1732113571 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7B390160003 X-Stat-Signature: t5xs8q3rodi6sdum4aebhq5cuznxe493 X-Rspam-User: X-HE-Tag: 1732113541-151586 X-HE-Meta: U2FsdGVkX19B4VEXTX7W1c58aH9LiWbebiUokHdkOwlI2v+PM6s7KaneKJJ1AoWIR1lYX3znQoTg+3nPN/MW62JYej+KiQ3O8JNhae+ajRh3K1QxzkiwOP3ucsYli0bwIEc1eb5/QAjDX932xSp711Q1flo8qfhcy2fSPgGaqs5yIJ5luSvos2Fzu+2LvdXCLrSulMdvRWI+ijzGzqKjk08UYGRfATrTWaBzENnkKG7zkDH6ndoAvR/vYroTAeEXmLxESOjERkAFKtBD+gE+1B99Dm4KEVRutKfyAuLig0L+wSxmlaXEA+8sUw/HL0R+Tmzcrbq4WPqUUzAHxWnoX84sUdWg3+IeKa0sWwf+L6NbwTgjjM0Nfn7fTUckd3sbTQG+hR/XJllM0ZHvCfR4TGXXSNxU6IDfacd59PJzEDmkLgLQDJCYnkl5s8MjEeqyVEGcjBgLC7sh6JG3Tmm83xW1PKdtihGKxlS88UCnHjf2tP0rhCjfvXnxxITTST4LAxtaRoJihzM0IOlqjqweN231UNqpZ3WssAV0jKA8NTNc2Uyf6/EcG4ymQ5qTkcDLQ5z013PmG8qUIMPQqoqavPBo5Tkh/OzGcKdo4XR2p4djPZERd3ZAYJ3Mc3ZlOVZwZnFRXyRyhGrdBEo9n6nCKjXbiICuBx47/sWq+D6XEGGtAEzqUsLPrnfe+64QGsXjtBynZOyQGHDe9BX19DYiT2PUqY6qSv9i9xgUIysDZkkwjKq3CWOAQG607fCCbcHrcKXWG7J41mI5IGdYkKDFEhU7GKeXMuImwcWdSilQiI/YvG6F3sGfJoqn7QinRdWNXY3M9bn2NOgAd5rG0UIgNYVxwlFEutLujR6DP3jZnPDm7hhE1fY07mA5b42ahhP/kRUNqWWrS12wIjM/Re5AeAs2MI4DYHTDkpbsKP2tQn83ac40tSYKVX7kVtA2mYC56ImyhDDgSDIFc2kRaQV 42qIT8L2 e1wnn/P6dx4gCwAQEyuNrvSwaqBJRnyimio4mpwYCricS8BDhnSBkKzpr1hjhWO82VpsEvCB62kjz/A5tELT8B32tBuuLFk2qIsVfvXDu2EwqwPpFnnjDkpbaEnoqdpVw3ULfKad7TXHIzifQRv5osifEs9A3d+QXfMYXkEuDzwCDPofGKqHFSKXWSSfKs5VzEfN4AImWQqjS7ZVr+bNHxQQI3WDunDF9B2FoOYf4tDc2WbOsjKfaAg/YxVySWqsmPhzhYVSCp8VWI0L+ZT5XOixkKqRDpHuDvzxCf03yHzB7jh9yru7JIyVbJIB8gjF6z21wnaiKrafJvQDhRPC5JaaRedYCDXVZCxepZl5QoDfxvVlPJNodVeOksUSPXFErm4vFkZDgbFOT3a4TK8eJ3XdFGCq1JGRDx7s/6zLwWS4oHs/yhGBpNwv/5UelaoAoNqeYeVN8YpISFQS2Cty77rdHhA== 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 20.11.24 15:05, Baoquan He wrote: > On 11/20/24 at 11:48am, David Hildenbrand wrote: >> On 20.11.24 11:13, Baoquan He wrote: >>> On 10/25/24 at 05:11pm, David Hildenbrand wrote: >>>> s390 allocates+prepares the elfcore hdr in the dump (2nd) kernel, not in >>>> the crashed kernel. >>>> >>>> RAM provided by memory devices such as virtio-mem can only be detected >>>> using the device driver; when vmcore_init() is called, these device >>>> drivers are usually not loaded yet, or the devices did not get probed >>>> yet. Consequently, on s390 these RAM ranges will not be included in >>>> the crash dump, which makes the dump partially corrupt and is >>>> unfortunate. >>>> >>>> Instead of deferring the vmcore_init() call, to an (unclear?) later point, >>>> let's reuse the vmcore_cb infrastructure to obtain device RAM ranges as >>>> the device drivers probe the device and get access to this information. >>>> >>>> Then, we'll add these ranges to the vmcore, adding more PT_LOAD >>>> entries and updating the offsets+vmcore size. >>>> >>>> Use Kconfig tricks to include this code automatically only if (a) there is >>>> a device driver compiled that implements the callback >>>> (PROVIDE_PROC_VMCORE_DEVICE_RAM) and; (b) the architecture actually needs >>>> this information (NEED_PROC_VMCORE_DEVICE_RAM). >>>> >>>> The current target use case is s390, which only creates an elf64 >>>> elfcore, so focusing on elf64 is sufficient. >>>> >>>> Signed-off-by: David Hildenbrand >>>> --- >>>> fs/proc/Kconfig | 25 ++++++ >>>> fs/proc/vmcore.c | 156 +++++++++++++++++++++++++++++++++++++ >>>> include/linux/crash_dump.h | 9 +++ >>>> 3 files changed, 190 insertions(+) >>>> >>>> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig >>>> index d80a1431ef7b..1e11de5f9380 100644 >>>> --- a/fs/proc/Kconfig >>>> +++ b/fs/proc/Kconfig >>>> @@ -61,6 +61,31 @@ config PROC_VMCORE_DEVICE_DUMP >>>> as ELF notes to /proc/vmcore. You can still disable device >>>> dump using the kernel command line option 'novmcoredd'. >>>> +config PROVIDE_PROC_VMCORE_DEVICE_RAM >>>> + def_bool n >>>> + >>>> +config NEED_PROC_VMCORE_DEVICE_RAM >>>> + def_bool n >>>> + >>>> +config PROC_VMCORE_DEVICE_RAM >>>> + def_bool y >>>> + depends on PROC_VMCORE >>>> + depends on NEED_PROC_VMCORE_DEVICE_RAM >>>> + depends on PROVIDE_PROC_VMCORE_DEVICE_RAM >>> >>> Kconfig item is always a thing I need learn to master. >> >> Yes, it's usually a struggle to get it right. It took me a couple of >> iterations to get to this point :) >> >>> When I checked >>> this part, I have to write them down to deliberate. I am wondering if >>> below 'simple version' works too and more understandable. Please help >>> point out what I have missed. >>> >>> ===========simple version====== >>> config PROC_VMCORE_DEVICE_RAM >>> def_bool y >>> depends on PROC_VMCORE && VIRTIO_MEM >>> depends on NEED_PROC_VMCORE_DEVICE_RAM >>> >>> config S390 >>> select NEED_PROC_VMCORE_DEVICE_RAM >>> ============ > > Sorry, things written down didn't correctly reflect them in my mind. > > ===========simple version====== > fs/proc/Kconfig: > config PROC_VMCORE_DEVICE_RAM > def_bool y > depends on PROC_VMCORE && VIRTIO_MEM > depends on NEED_PROC_VMCORE_DEVICE_RAM > > arch/s390/Kconfig: > config NEED_PROC_VMCORE_DEVICE_RAM > def y > ================================== That would work, but I don't completely like it. (a) I want s390x to select NEED_PROC_VMCORE_DEVICE_RAM instead. Staring at a bunch of similar cases (git grep "config NEED" | grep Kconfig, git grep "config ARCH_WANTS" | grep Kconfig), "select" is the common way to do it. So unless there is a pretty good reason, I'll keep NEED_PROC_VMCORE_DEVICE_RAM as is. (b) In the context of this patch, "depends on VIRTIO_MEM" does not make sense. We could have an intermediate: config PROC_VMCORE_DEVICE_RAM def_bool n depends on PROC_VMCORE depends on NEED_PROC_VMCORE_DEVICE_RAM And change that with VIRTIO_MEM support in the relevant patch. I faintly remember that we try avoiding such dependencies and prefer selecting Kconfigs instead. Just look at the SPLIT_PTE_PTLOCKS mess we still have to clean up. But as we don't expect that many providers for now, I don't care. Thanks! -- Cheers, David / dhildenb