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(p200300d82f239c00d1f6f7fe8f147e34.dip0.t-ipconnect.de. [2003:d8:2f23:9c00:d1f6:f7fe:8f14:7e34]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45b98e77231sm303120095e9.12.2025.09.09.02.21.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Sep 2025 02:21:56 -0700 (PDT) Message-ID: Date: Tue, 9 Sep 2025 11:21:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/7] Nesting support for lazy MMU mode To: Andrew Morton , Kevin Brodsky Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alexander Gordeev , Andreas Larsson , Boris Ostrovsky , Borislav Petkov , Catalin Marinas , Christophe Leroy , Dave Hansen , "David S. Miller" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Juergen Gross , "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> <20250908191602.61160a7990b9ea418de758c7@linux-foundation.org> 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: <20250908191602.61160a7990b9ea418de758c7@linux-foundation.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xKZBug1IFDELyMXg7yiLHP8j5Bxde46Z7Zhl3mv4Sq4_1757409718 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 9D1B140008 X-Rspamd-Server: rspam05 X-Stat-Signature: jnubkue11pf1xs49csi6jz33w4w7b5xy X-Rspam-User: X-HE-Tag: 1757409720-36687 X-HE-Meta: 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 q7IofIHI rn2ythJtElJ5s+1iWzM/MJT57zMfh+DTWxfPS7yL13XAmIHHQ0rqqX7PaPQgcEsgW3NibkWdyyr+cI5eNaOJQva9Ahngg7mBjH7E+qAPljC8FEYOyZhA8d2vfhcKMlp2swMaF0WIvFU9aOH/Lb9o3BwrsrBpGaEARTYrYO6SEEaGyyGKFeAh5iXCRdhqjEPOaTIqnUf3X/llXVUGLHyPXl63oNwmdjlaogK4PiY+Fo3LnMR5lGL+3+TTqixHzCOBfu4Jzg4PyGtafIotefpP0BsDp7XkX/L6ypIgyNc+an4Ds0B7Bjf3Ep7zKpPZ0idQJeuAfPSgQ0zm1XdKxlXa/eTEU9Pk0OU+DxT8zYRYfoaur7Z6wMJYXlirH/vTEgn0cngEBPPQ20gzAOIQRSgRA7YUyeDL79Qsi5x21bB67MqXaggkLKZU++uryGqNxS2TXMw9SXC3gJ+ReafJ2dHez62hdsE3cLUhqmicRVpcjl9j1Qg8= 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 04:16, Andrew Morton wrote: > On Mon, 8 Sep 2025 08:39:24 +0100 Kevin Brodsky wrote: > >> The main change enabling nesting is patch 2, following the approach >> suggested by Catalin Marinas [4]: have enter() return some state and >> the matching leave() take that state. > > This is so totally the correct way. Thanks. Staring at this, I wonder if we could alternatively handle it like pagefault_disable()/pagefault_enable(), having something like current->lazy_mmu_enabled. We wouldn't have to worry about preemption in that case I guess (unless the arch has special requirements). Not sure if that was already discussed, just a thought. -- Cheers David / dhildenb