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 008B6C282C6 for ; Mon, 3 Mar 2025 11:52:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 86AAB280003; Mon, 3 Mar 2025 06:52:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 81B18280001; Mon, 3 Mar 2025 06:52:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6946F280003; Mon, 3 Mar 2025 06:52:41 -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 4AAC2280001 for ; Mon, 3 Mar 2025 06:52:41 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id C99C01607F8 for ; Mon, 3 Mar 2025 11:52:40 +0000 (UTC) X-FDA: 83180077680.02.5C22750 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 6E197160008 for ; Mon, 3 Mar 2025 11:52:38 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bMascYiT; 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=1741002758; 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=WCQNb4Zwl01zkLUWNEjK6UzQKXJ+OotwjxENzLzaBD0=; b=lofJ312pf/8+Eq3gzYTRazhDzVzaBYgEszsz+eklDoAVnDfXCkSGN1ctzgMitOvFKJEUC1 mI71WXZPEKCKOpGN+8QlpYYF2+0bMTc3nENNxtXz4TBaOZKTYG2IitXqfX50JUp1N7jQCk B1TZ/unsW+r9t3iIxW7RmayW0fEaKH4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1741002758; a=rsa-sha256; cv=none; b=xOJV4xFcVGKD5qFFogzu/K5VO5UhkazXdgl/ufqzRy4i3BUQ2AM0+8R65uOSnWLzwXNOTx /AVVqUOXw7wVwkM153cMy5Ax0daRZzIYYtS4PS8wEDJFMlpgmtD+QAmT2Io8tpYIDvYyCX PAEXW1sKXLG900ivVDRC8uE1wJYXlUI= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bMascYiT; 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 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741002757; 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=WCQNb4Zwl01zkLUWNEjK6UzQKXJ+OotwjxENzLzaBD0=; b=bMascYiT2wgL/inxHfi4qt/Pm30DaaKgGh6EQ7YtHHw1PoKlrLC6OZooGH+8QvmTu1Dkre sTqdtAj2JS8Gp6dvzH3aL9Xmd+lOzknwaES5sFseNUbDwQgD2dTu8T4AlR49Lw/uZZEtlT c0VceWPh0XWMdpdnI+D6cLgS3/sevY0= 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-54-a9Mo44WsPRGILDsHuSfHPg-1; Mon, 03 Mar 2025 06:52:36 -0500 X-MC-Unique: a9Mo44WsPRGILDsHuSfHPg-1 X-Mimecast-MFC-AGG-ID: a9Mo44WsPRGILDsHuSfHPg_1741002755 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4399a5afc72so19195755e9.3 for ; Mon, 03 Mar 2025 03:52:36 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1741002755; x=1741607555; 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=WCQNb4Zwl01zkLUWNEjK6UzQKXJ+OotwjxENzLzaBD0=; b=Z0+zMhS6bsZQWGpwlzMO9vmd0+oHpXFwc5CA+i27MwFKv2gfoQzobnMEnD2osKFbeg Ty9iccuF3m9mmCDmjEY04vqwmnBywmv6VmajrJPZ4H8c1IK8smuXiBxpKcx1qET+cEWt LVrALexyIk5Br+M8eTzCLN6AIQx45zi3HYn7JOe+W/b0JLhANEVrzTPzm1kqr9iOVHYk 62HAudtSuCD1fwU974VreFrABaMApk45oM8eq0Eg0O/HW3rjVP6MZSvHdiW0iQpUECXu OoamyliF/+MTkqKrXsoIKq6/d/GaShDlT7HdY++EKAGwFWD0Y6JJS65xoCw6YwyYZCbP E4MA== X-Gm-Message-State: AOJu0Yz7/aoqbp7zFgnIotqibNQ/oVN+y8Gmz+1VRt0E8+C+rT9A7m9N 3S03zrzcb0MDac8UpXfHi5Sm+xvoikBFUFlRb3kngLXA7tjmSAZDm46ChJDm0Tr3/qpPJMv/wDE NYBzHsT5NpN/cFmr+U48Jat1CE7o6olYWLdFKtHcZLZRmU0XU X-Gm-Gg: ASbGncuv4kUt1GrFpk3vH6V8y5q8gqCCgcCITu7OW3CIPJStkz6VDNBBFT5seIRDDsd yQfr4yDji0G68iu9R+6FckYNMGe0hd8sqcIViSrYPt0FvxXkuS4WuN1jJhHgEVTSRSeG5+cIgC+ DELUP/9SxS0aQebuOci2aFaFK429xaqdCaPll+Nm/4hqzf2qXIdCM1H0raGeX/1PYK7G/4lY3ZN miwNTYsh29xMT5NzEm2/w924+VKXan4fwTfmXhIOTlOFyp2RH98Jy7iySOyVd5zUvryKwvVCE3L nztjtvGNg12mklLmY/zyKgbEOHk36tjZMLCyfx9d923AHVHa7fyxFXUCrdWV7lqj4bE1PXtpBPo bb3KfmBb9OTDiD3DHBxZXGBaan07dh0KnHSUMeJPFaBk= X-Received: by 2002:a05:600c:3ca8:b0:439:a88f:8523 with SMTP id 5b1f17b1804b1-43ba6760622mr91900315e9.21.1741002755404; Mon, 03 Mar 2025 03:52:35 -0800 (PST) X-Google-Smtp-Source: AGHT+IFTSfsUTkoO/or2iqdtsglYhk9ASXd3bpPBU2UgU+xONmgHuMQAHjbX/a34a1saMfjcf6uKjg== X-Received: by 2002:a05:600c:3ca8:b0:439:a88f:8523 with SMTP id 5b1f17b1804b1-43ba6760622mr91900045e9.21.1741002755055; Mon, 03 Mar 2025 03:52:35 -0800 (PST) Received: from ?IPV6:2003:cb:c734:9600:af27:4326:a216:2bfb? (p200300cbc7349600af274326a2162bfb.dip0.t-ipconnect.de. [2003:cb:c734:9600:af27:4326:a216:2bfb]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43aba5711fcsm193432675e9.28.2025.03.03.03.52.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 Mar 2025 03:52:34 -0800 (PST) Message-ID: <75031fe1-50d7-48d0-87bb-9c5c88f3b41c@redhat.com> Date: Mon, 3 Mar 2025 12:52:33 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 4/4] Revert "x86/xen: allow nesting of same lazy mode" To: Ryan Roberts , Andrew Morton , "David S. Miller" , Andreas Larsson , Juergen Gross , Boris Ostrovsky , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , "Matthew Wilcox (Oracle)" , Catalin Marinas Cc: linux-mm@kvack.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org References: <20250302145555.3236789-1-ryan.roberts@arm.com> <20250302145555.3236789-5-ryan.roberts@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: <20250302145555.3236789-5-ryan.roberts@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: K_BuzmLYJ6o7Jk25bVGghHdgiGgQBjnt79cfOD8dHT0_1741002755 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: rspam02 X-Stat-Signature: 11j3d6rgb5bo5kekmtkc3u9mug86doym X-Rspamd-Queue-Id: 6E197160008 X-Rspam-User: X-HE-Tag: 1741002758-91938 X-HE-Meta: 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 BijmuJCt LgkkxAFIGcMjbQvMiNq313Hrc64F432T36z1NJLnvtJdfQ1o9QsthWdm66HoIQqgekQJJCiS3zL7WWsNwgAhWEUBxKS6xVkklwwm5N6EpOjnQZjKyNhDvHO55F3vgAOjp0FbsWEggJoN0p71pfo5/+R83DF5y8Ml8XMlvkr8ah9mV5bvTt8rQI54/uf4mUmLbgOFLyKf1ldOqeGNe05qJFA2v3y0mex+EWHxw50cNzGwWg0Uq5gOWC25MTZYKRRUSxjicK0w5NHBIgpmQi1P7x58OD1vZ2njcqUrk+a1BREXk1HM0Solqu296edH+zr1s60YdGPtonwV2tWlBV+eytf1a3PEFvHHD7jgokkxdZ2b+5L4Kudj/rytgltfZ4JeKVEaxEkaDQkY+uZrrzC0e/83v5B+w9acgktS7lvH4vB4d1nr5EVO8kwDp1wMlv+1mLwz8OxwpjV47LtsV1G0bqknOTCAOIsCb0H6F 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 02.03.25 15:55, Ryan Roberts wrote: > Commit 49147beb0ccb ("x86/xen: allow nesting of same lazy mode") was > added as a solution for a core-mm code change where > arch_[enter|leave]_lazy_mmu_mode() started to be called in a nested > manner; see commit bcc6cc832573 ("mm: add default definition of > set_ptes()"). > > However, now that we have fixed the API to avoid nesting, we no longer > need this capability in the x86 implementation. > > Additionally, from code review, I don't believe the fix was ever robust > in the case of preemption occurring while in the nested lazy mode. The > implementation usually deals with preemption by calling > arch_leave_lazy_mmu_mode() from xen_start_context_switch() for the > outgoing task if we are in the lazy mmu mode. Then in > xen_end_context_switch(), it restarts the lazy mode by calling > arch_enter_lazy_mmu_mode() for an incoming task that was in the lazy > mode when it was switched out. But arch_leave_lazy_mmu_mode() will only > unwind a single level of nesting. If we are in the double nest, then > it's not fully unwound and per-cpu variables are left in a bad state. > > So the correct solution is to remove the possibility of nesting from the > higher level (which has now been done) and remove this x86-specific > solution. > > Fixes: 49147beb0ccb ("x86/xen: allow nesting of same lazy mode") Does this patch here deserve this tag? IIUC, it's rather a cleanup now that it was properly fixed elsewhere. > Signed-off-by: Ryan Roberts Acked-by: David Hildenbrand -- Cheers, David / dhildenb