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 E08C1C4345F for ; Tue, 16 Apr 2024 13:41:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3FBE76B0082; Tue, 16 Apr 2024 09:41:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3AB156B0083; Tue, 16 Apr 2024 09:41:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 24C066B0085; Tue, 16 Apr 2024 09:41:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 06C776B0082 for ; Tue, 16 Apr 2024 09:41:32 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 87D72408B6 for ; Tue, 16 Apr 2024 13:41:31 +0000 (UTC) X-FDA: 82015507182.01.1D5E148 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf26.hostedemail.com (Postfix) with ESMTP id 392DA14000F for ; Tue, 16 Apr 2024 13:41:29 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VP1zk27Y; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf26.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 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=1713274889; 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=Dr11CEnQo6o/6WX8/bz57IHiwW8Fb6G/zTIFdQaHNpo=; b=VoSOrNxmChce+nMJ5vF7vfaA/o2lUAQI+u6ENMYNfXaRKMAUo4aAIjW5V1/dxxpTW4Ifgi vymdHOBA+8BrLq6wnVdLlPYeGOI1TxsJXKo7RJ165zMZ0YLfT07kmvY+ES7YbBXL0xWD1C H1MSK1JxmJSjxysDP7yhHSLJ1uLg0pg= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VP1zk27Y; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf26.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1713274889; a=rsa-sha256; cv=none; b=AOB1rTAuxV9jdXXeuQGxFh6mEp3HyzZAP+QZuV3upoAJCS8omjh7W1UzotQhDr+RG1Rbxd w277lf8FzITF9KlTjZxCjS0p1AyjzpCntRw6V0kI++O5uFalP6hfWJdN3EXXwPMBM3vN2o RHxxifbDTkgFosnl4EbVIAJaMWn0b/8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1713274888; 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=Dr11CEnQo6o/6WX8/bz57IHiwW8Fb6G/zTIFdQaHNpo=; b=VP1zk27YAwtJM2dXmXHBeLxEaBa0xkhTRHa8cSEq+zopO3krM1nsyngqJVZDo9jDFY387f hVmtxa2HZDkGvOvqO0+WOrPSaT2wcV60kGG1cV7ZXPD0mFkAcDnVuCQmPykfL6Bixt1CPQ Si3rnLP+12Sx40y2e5i2hgkFxwOtPgg= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-522-lcqmQylIOUin7qPAKmZW5w-1; Tue, 16 Apr 2024 09:41:24 -0400 X-MC-Unique: lcqmQylIOUin7qPAKmZW5w-1 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-343e46df264so2296723f8f.1 for ; Tue, 16 Apr 2024 06:41:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713274883; x=1713879683; 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=Dr11CEnQo6o/6WX8/bz57IHiwW8Fb6G/zTIFdQaHNpo=; b=p6xstFlVCYQ3ldT/hfUvhZkrKEX1nIYD0eLD3iKbftG2AOnW9zHFYXSWJBt6nyrdrl yMwwph9Vd/4xRuWSiGV2vNDkP1z/9TOyC5FgkCRSplAIclt1b53YgKoYm1iH8ZGkqgYe BP10QS2c4ovBs9vp52i6TfY9OtC/fF6fgud1nDahtOSgeMoooOxBstLexNibX0V2l4wf NI9l+A62hXeQSMBjzfxRnvMDUmALzwbTb+fviEBFlDW6loT/0DLzpVTv36y06THkpLby G2SUx1VPpgHdgbXTC3D3M6VdJA6okx8A2d4t9KZLxBVBf8xGBnnbMW7uhclZshjUhx/C jL+Q== X-Forwarded-Encrypted: i=1; AJvYcCXFAJ0Xl0gD+whfjSb8B0uIaCYKRApQEuGNQDqiWLij31UfXWbAlymUQ4yQS7cZAVBuHvLttJGScL/LP/vE724ARww= X-Gm-Message-State: AOJu0Yyf6V5R/Qc06nE1WBhkhke6bLiWbK3r8jaaJt47xJxbPnmDASLO rqwbp36qWdFbZcavOXMonsL2zvYvC8sbxsqrf0VpmGTwv4f05vB+Zuqfm/7UxJsbb6EZ0ThqsCR urtv5QGHFdcULclTGOVbmx+Dmev6VzOIWygwWVpwaywiigCN+ X-Received: by 2002:a05:6000:402c:b0:346:1ab6:dbd5 with SMTP id cp44-20020a056000402c00b003461ab6dbd5mr11590286wrb.20.1713274883588; Tue, 16 Apr 2024 06:41:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH0jglEtIQZrQU4VrAnm9UUOQbxIDrqeVHpWbaKbj+NgBBw4aE4d2eyNf/fl5AEwN4YQPjSIg== X-Received: by 2002:a05:6000:402c:b0:346:1ab6:dbd5 with SMTP id cp44-20020a056000402c00b003461ab6dbd5mr11590249wrb.20.1713274883090; Tue, 16 Apr 2024 06:41:23 -0700 (PDT) Received: from ?IPV6:2003:cb:c718:6400:7621:b88a:e99e:2fa8? (p200300cbc71864007621b88ae99e2fa8.dip0.t-ipconnect.de. [2003:cb:c718:6400:7621:b88a:e99e:2fa8]) by smtp.gmail.com with ESMTPSA id m4-20020adff384000000b0033e7de97214sm14871567wro.40.2024.04.16.06.41.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 Apr 2024 06:41:22 -0700 (PDT) Message-ID: Date: Tue, 16 Apr 2024 15:41:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] s390/mm: re-enable the shared zeropage for !PV and !skeys KVM guests To: Christian Borntraeger , Alexander Gordeev Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Janosch Frank , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Andrew Morton , Peter Xu , Sven Schnelle , Gerald Schaefer , Andrea Arcangeli , kvm@vger.kernel.org, linux-s390@vger.kernel.org References: <20240411161441.910170-1-david@redhat.com> <20240411161441.910170-3-david@redhat.com> <8533cb18-42ff-42bc-b9e5-b0537aa51b21@redhat.com> <20d1d8c5-70e9-4b00-965b-918f275cfae7@linux.ibm.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: <20d1d8c5-70e9-4b00-965b-918f275cfae7@linux.ibm.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: 7bit X-Rspam-User: X-Stat-Signature: jxne9cyp9ka94m1udtprwo798hpu67qz X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 392DA14000F X-HE-Tag: 1713274889-801775 X-HE-Meta: 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 AiIjhdi0 kjBI7GnzhEW9CtjOeLTsadv4aSDpsqGVbc0Q2DHWStbKipu7lspEytMgwJtPdI0Gf6N7PDwiOHae+mFGQyuySKNNCcofIlUvH6Lpwnqg7T7fdOix8e12wzxVcQe/tFfaZmj5X1sedr5aucf8a3GiGKzIQusD75hzxwPn6Oyh64ALd/gKou4Lh3gu7Aaq/BV/V+eJQpND1ebstix0tFkQgr0bA9evd0E4u5DOs5QdO1A0Gat9htd30F7F48BxIT/id2pmMWUcWO/yan7ze8O233LUVKC832K6jSFZxv5vBa1WXbPS8br17ImwVJRBr6zDrclcjc3y7Ou1inHWPNkJcX9Fe+gAhnmS3jRGBihVlSOoDsSKH1d95Fv/vJXcOR8+hHo5YOuKi2w8GtNUGSGEE/Tt8VaY5fFeUXO1SMz1KFD5eYKJsW5v85U+bBfjRahI6VjJETvxVoO2T42BXyDyDOPNGnw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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 16.04.24 14:02, Christian Borntraeger wrote: > > > Am 16.04.24 um 08:37 schrieb Alexander Gordeev: > >>> We could piggy-back on vm_fault_to_errno(). We could use >>> vm_fault_to_errno(rc, FOLL_HWPOISON), and only continue (retry) if the rc is 0 or >>> -EFAULT, otherwise fail with the returned error. >>> >>> But I'd do that as a follow up, and also use it in break_ksm() in the same fashion. >> >> @Christian, do you agree with this suggestion? > > I would need to look into that more closely to give a proper answer. In general I am ok > with this but I prefer to have more eyes on that. > From what I can tell we should cover all the normal cases with our CI as soon as it hits > next. But maybe we should try to create/change a selftest to trigger these error cases? If we find a shared zeropage we expect the next unsharing fault to succeed except: (1) OOM, in which case we translate to -ENOMEM. (2) Some obscure race with MADV_DONTNEED paired with concurrent truncate(), in which case we get an error, but if we look again, we will find the shared zeropage no longer mapped. (this is what break_ksm() describes) (3) MCE while copying the page, which doesn't quite apply here. For the time being, we only get shared zeropages in (a) anon mappings (b) MAP_PRIVATE shmem mappings via UFFDIO_ZEROPAGE. So (2) is hard or even impossible to trigger. (1) is hard to test as well, and (3) ... No easy way to extend selftests that I can see. If we repeatedly find a shared zeropage in a COW mapping and get an error from the unsharing fault, something else would be deeply flawed. So I'm not really worried about that, but I agree that having a more centralized check will make sense. -- Cheers, David / dhildenb