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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 39FC3CAC587 for ; Tue, 9 Sep 2025 09:57:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8E2176B00AC; Tue, 9 Sep 2025 05:56:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 88BAF8E0017; Tue, 9 Sep 2025 05:56:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 72D818E0001; Tue, 9 Sep 2025 05:56:59 -0400 (EDT) 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 5B8E16B00AC for ; Tue, 9 Sep 2025 05:56:59 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 27AA81A03C2 for ; Tue, 9 Sep 2025 09:56:59 +0000 (UTC) X-FDA: 83869258158.02.ECE787A Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf11.hostedemail.com (Postfix) with ESMTP id D406440003 for ; Tue, 9 Sep 2025 09:56:56 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Tzu7Ddkv; spf=pass (imf11.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1757411816; 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=v9v9HEY+peb6y/djARujyPjanSQs6bY1lozPYtVGaPg=; b=ZJF3A5YlpayAmhBPusDDV8g25SjGHSuSH44ZRvwwJn0LaxPiDrSOj5yhayw/w7mBE0/pvE Sm2T9tWISTH3M/VUsgi3fGKXNl3zswAo2Rzyxm/cN1qMedZcV85jfk1jym3qES0nMWDgD6 W+FoE0PC9BjMJrDs+zAHIeBPV3widng= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Tzu7Ddkv; spf=pass (imf11.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1757411816; a=rsa-sha256; cv=none; b=qyxC1h2YawnCKXzf/Bc8Ki1Ahm5DGDwFJQt9RqtsB6kBlXuY1E9gjWc8bf8DmUgZN3z6Km RqSZKikbEWphjtJpHI6pXwlNHbMK1l1bJVVgUh9WRrdnslD8tCh5jkZfQ4/W7qvBF8/9Q5 X8qpBIyuhUe47I8HBc8pIFhAQLcK6rQ= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757411816; 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=v9v9HEY+peb6y/djARujyPjanSQs6bY1lozPYtVGaPg=; b=Tzu7DdkvQzs7M1WEFk9+yZ2wOjVaifo7TX98jxaeX/rSaERnI2FL3cQ/eEyudYaLMHNbo4 zp06tZLvLJEYPrqheo7YjReLalxFlvyPABOUVR310KyBUFZH+rgTLO+ROhjD7p0uWyJ9VA aFZyY6Hy5lOSV+WbwReHvZRAKJRQBpU= 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-693-Aj_yua9pOsynZ43Ar328yw-1; Tue, 09 Sep 2025 05:56:53 -0400 X-MC-Unique: Aj_yua9pOsynZ43Ar328yw-1 X-Mimecast-MFC-AGG-ID: Aj_yua9pOsynZ43Ar328yw_1757411812 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-45dde353979so18108785e9.3 for ; Tue, 09 Sep 2025 02:56:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757411812; x=1758016612; h=content-transfer-encoding:in-reply-to: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=v9v9HEY+peb6y/djARujyPjanSQs6bY1lozPYtVGaPg=; b=OBjNA2LGCEQzyUKKM8l0/tkwgfQ0JhVOrhFpVZdD4qxrOD+9e3SteKcJXu9xIVB8oG aU00oZe5k8xyV7eZ2OfiFOP1OujW6eXLWf+azTQHqgVLZtz+wq7RquoswUuZS6SzNS+N mZop0GBodzFSspeHs1mVQWh5XKfTYhMQ6aSAFTjUI5DN6m5ufyVnOYVZ1vd4+PWahoc8 dC6WwOgsOR2r9kcAGNEa2//cXEpYUz6EYrcAbRKUhuOk2iu59GUhG551E5FdGZ4f1k0H w+4mK7mYcenXxfWh2PT7VLh8O1s83GBtMxNCl8ww58dWHYJ3UwP3fCNpCDEQBaM1O7Fy Wqjg== X-Forwarded-Encrypted: i=1; AJvYcCWihHfMKo36Mk8sldCZFunVdOB8k2Z+rjXIdYZjqB4AjAwr0lpN5zPaBW62yYGb4IFC8lDQN9fvmw==@kvack.org X-Gm-Message-State: AOJu0Ywl1aGC6XLS5fZVwbPDGWzUM6g6z1v/B/8dxzTatgN9SstjI9VH sjveqf59Deb5eFiVY007CaYANkqGwDviMzsRkP+KXxQ+EaSVDTnOifu9YjRKzq/0NcFL77x09O5 /DYbfLfSF1/+SRQzK2SNmpIdxD12odHswyZY/Dk3GTDJpnxp9VMlW X-Gm-Gg: ASbGncuufMu1g3PuJnC44PWFUlVM9k+xKic127DnxL2VY4Y9R272mVcTQ1GtAbj6fmS syQyE8/PRNFrwUNdYG6wsStRuhJuw4ZjI9kS+1Iwh/xE+rThFlaMMbQGIq1MEus503oJAydJJO8 /1uFEYaaq6Iqr/INI/sD6tMjYFyuuR3Ni2YdqGcrJ9wG+59AJyPBVMbmAx0vWafOxF4kI9dI+l+ Qp39bRrW7xN/T+mXVuPWrIQmceQN1zPk3rxWQ2fTg9fHz7gVYu1p/lx4tsGiFgwF4gmZKJ5AojY CCX+Ib0u1RjveJFiajE4lLbNFaMXch2UJNeyP53bmEExt4IMWgIUk5CLv0kdqwBXdQjUKWY9ihK U7crseT1GkoJlp7hBo1NGRUIzG7nsw37dLldChhvkiyrnCROpvhMy1EQH+U5YG8O9JNc= X-Received: by 2002:a05:600c:3b83:b0:450:6b55:cf91 with SMTP id 5b1f17b1804b1-45de3c20088mr82989945e9.6.1757411811938; Tue, 09 Sep 2025 02:56:51 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHxA/lg+jOMLOS5VKnviegUlnV1FAVtarDrgFAYvQcjN5JtjPJvVcivfNI/KeNLfzLwRHX8LA== X-Received: by 2002:a05:600c:3b83:b0:450:6b55:cf91 with SMTP id 5b1f17b1804b1-45de3c20088mr82989315e9.6.1757411811384; Tue, 09 Sep 2025 02:56:51 -0700 (PDT) Received: from ?IPV6:2003:d8:2f23:9c00:d1f6:f7fe:8f14:7e34? (p200300d82f239c00d1f6f7fe8f147e34.dip0.t-ipconnect.de. [2003:d8:2f23:9c00:d1f6:f7fe:8f14:7e34]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45df16b2971sm5934435e9.7.2025.09.09.02.56.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Sep 2025 02:56:50 -0700 (PDT) Message-ID: <57f49b72-2126-48f0-a4ef-4b138bd0bead@redhat.com> Date: Tue, 9 Sep 2025 11:56:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/7] x86/xen: support nested lazy_mmu sections (again) To: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= , Kevin Brodsky , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Alexander Gordeev , Andreas Larsson , Andrew Morton , Boris Ostrovsky , Borislav Petkov , Catalin Marinas , Christophe Leroy , Dave Hansen , "David S. Miller" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , "Liam R. Howlett" , Lorenzo Stoakes , Madhavan Srinivasan , Michael Ellerman , Michal Hocko , Mike Rapoport , Nicholas Piggin , Peter Zijlstra , Ryan Roberts , Suren Baghdasaryan , Thomas Gleixner , Vlastimil Babka , Will Deacon , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org References: <20250908073931.4159362-1-kevin.brodsky@arm.com> <20250908073931.4159362-5-kevin.brodsky@arm.com> <360712fa-f7a0-4674-acc4-76f79141fe4f@suse.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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <360712fa-f7a0-4674-acc4-76f79141fe4f@suse.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: uJ1x5bwSKArvWQ-lXztUPiS0ZcxTjfzhWz6vD4NsWYQ_1757411812 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: D406440003 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: r1wktzgig6wpr5fho95saqdn7r3oojbo X-HE-Tag: 1757411816-714505 X-HE-Meta: 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 /X9YAumG wwiPnNhD9uXsCyZWGp4Dlcy4tf3IUvQ1IvhK6SsFX31zn5RhGrgEFkxMA4XFFB6tG6ATVyd33G4Z/bzPJxxuhfRPU1YSkWiCeqPC30E6v/V3tuF7yNySzMRxhBLc5hzZgHbPctdSgQ55ZO+Jv5sbgxrf0m+f3WqVx2cdK4A0DUjCZJdCF0aC4G1wqAkeVyx3e4XG5byZLWeVvAnVUC82Yr0BYc17JsvFLO97hTtIutIPPITVHmmq40bMCZ7JpHIsOw6w6aNWohE54vOoyROxdZGoezlDyLpVOVaZ0agc0eG8hB4FoonGt7HLL9LDqeCU1EEE5xyRstNV/LHh1drA5qYyjl6AYprkZJZF6jgDdhsa8tOXyChbXPTh+YDF0BBRaQjhxRGBsRLWbPyX15y5BhCfWSTqiqdD6LIF/Y0ZZKi5hINOS9hZs823vwCqVnMjijw37HifsTSKDQ4p1d8nOQSfjJLBaFuWVKCoaW5DyuohhXzdpe6hoFSma72XNfh6ecV0U19SfF0KQlc/D2SD3BteKfp2b2N6orK66B2j9hN3vdfEdG7lt59qtCg== 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 09.09.25 11:37, Jürgen Groß wrote: > On 09.09.25 11:13, David Hildenbrand wrote: >> On 08.09.25 09:39, Kevin Brodsky wrote: >>> Commit 49147beb0ccb ("x86/xen: allow nesting of same lazy mode") >>> originally introduced support for nested lazy sections (LAZY_MMU and >>> LAZY_CPU). It later got reverted by commit c36549ff8d84 as its >>> implementation turned out to be intolerant to preemption. >>> >>> Now that the lazy_mmu API allows enter() to pass through a state to >>> the matching leave() call, we can support nesting again for the >>> LAZY_MMU mode in a preemption-safe manner. If xen_enter_lazy_mmu() is >>> called inside an active lazy_mmu section, xen_lazy_mode will already >>> be set to XEN_LAZY_MMU and we can then return LAZY_MMU_NESTED to >>> instruct the matching xen_leave_lazy_mmu() call to leave >>> xen_lazy_mode unchanged. >>> >>> The only effect of this patch is to ensure that xen_lazy_mode >>> remains set to XEN_LAZY_MMU until the outermost lazy_mmu section >>> ends. xen_leave_lazy_mmu() still calls xen_mc_flush() >>> unconditionally. >>> >>> Signed-off-by: Kevin Brodsky >>> --- >>>   arch/x86/include/asm/paravirt.h       |  6 ++---- >>>   arch/x86/include/asm/paravirt_types.h |  4 ++-- >>>   arch/x86/xen/mmu_pv.c                 | 11 ++++++++--- >>>   3 files changed, 12 insertions(+), 9 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h >>> index 65a0d394fba1..4ecd3a6b1dea 100644 >>> --- a/arch/x86/include/asm/paravirt.h >>> +++ b/arch/x86/include/asm/paravirt.h >>> @@ -529,14 +529,12 @@ static inline void arch_end_context_switch(struct >>> task_struct *next) >>>   #define  __HAVE_ARCH_ENTER_LAZY_MMU_MODE >>>   static inline lazy_mmu_state_t arch_enter_lazy_mmu_mode(void) >>>   { >>> -    PVOP_VCALL0(mmu.lazy_mode.enter); >>> - >>> -    return LAZY_MMU_DEFAULT; >>> +    return PVOP_CALL0(lazy_mmu_state_t, mmu.lazy_mode.enter); >>>   } >>>   static inline void arch_leave_lazy_mmu_mode(lazy_mmu_state_t state) >>>   { >>> -    PVOP_VCALL0(mmu.lazy_mode.leave); >>> +    PVOP_VCALL1(mmu.lazy_mode.leave, state); >>>   } >>>   static inline void arch_flush_lazy_mmu_mode(void) >>> diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/ >>> paravirt_types.h >>> index bc1af86868a3..b7c567ccbf32 100644 >>> --- a/arch/x86/include/asm/paravirt_types.h >>> +++ b/arch/x86/include/asm/paravirt_types.h >>> @@ -45,8 +45,8 @@ typedef int lazy_mmu_state_t; >>>   struct pv_lazy_ops { >>>       /* Set deferred update mode, used for batching operations. */ >>> -    void (*enter)(void); >>> -    void (*leave)(void); >>> +    lazy_mmu_state_t (*enter)(void); >>> +    void (*leave)(lazy_mmu_state_t); >>>       void (*flush)(void); >>>   } __no_randomize_layout; >>>   #endif >>> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c >>> index 2039d5132ca3..6e5390ff06a5 100644 >>> --- a/arch/x86/xen/mmu_pv.c >>> +++ b/arch/x86/xen/mmu_pv.c >>> @@ -2130,9 +2130,13 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t >>> phys, pgprot_t prot) >>>   #endif >>>   } >>> -static void xen_enter_lazy_mmu(void) >>> +static lazy_mmu_state_t xen_enter_lazy_mmu(void) >>>   { >>> +    if (this_cpu_read(xen_lazy_mode) == XEN_LAZY_MMU) >>> +        return LAZY_MMU_NESTED; >>> + >> >> You mention above "preemption-safe manner" above, so I am wondering, >> what if we get preempted immediately after doing the this_cpu_read() and get >> scheduled on another CPU? >> > > This should still be correct: preemption needs a context switch to happen, > so xen_start_context_switch() and xen_end_context_switch() are involved. > Those are dealing with this problem by doing the right thing in the old > and the new context. Thanks, that makes sense. Would be valuable to add that detail to the patch description. -- Cheers David / dhildenb