From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 281F42C11FA; Fri, 26 Jun 2026 19:50:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782503426; cv=none; b=PrqWgalOV9yGqQGwBZ7F2Ut+gUbohh+MWEJqBYieZD4ejzxAKqOp7VdGpP6uJDAVKkX/gDUJHGpUlzOHSPfn8dbBpfff4OhxrkiBH2ZE9+zisRtYRPoE/vkcpg87Ds/IPt1XTu9FIyzRiCYJ8uW0Y3+5/pgqZRLSqtteGwy7QkY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782503426; c=relaxed/simple; bh=lT+J7ntDQg5Nr3PwVJjTputY3hGSGGM5pFtpG1JUg1c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TZXSYvDVoZ5BpQZAcRLgTeqlH5CCjDg6PmDQMEghaS2ocyRGACfVGOCY6+wXVmiD9SvpmIIqRCg5U5RBdy5/p2NpP64FDS1Is4gICopQTJPJtVBYYGfjM30hHfj6b6S3TlKgjBNmftiuoLRHcoYpj1CwinyxK5kcRvrHCM856ig= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NTtUQXvN; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NTtUQXvN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4CBF11F00A3A; Fri, 26 Jun 2026 19:50:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782503425; bh=+t6TSyTiAKLXeeEOFDCg8Jg8JM8h6Pi7hm6oO1fXx5k=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=NTtUQXvNaFQOhqaf/UXBVWk/qgdqvRJGRJ5OMmFK0PyEFVD0EjAckGe/PeB2YGYTG gMLdSTptFE77czP2kttaaXC500/s9w2v5s/Tz9O5h6YfuqqvliR2Z3B9B7/H7LYsDB rjknYXL073VAy+GQv1nZF7cmRWpzSaomG2OWMmrrqH13r45SFX6+yjAFKOT0GBGtvE Mn8/vUXVtEDvs4OG1WwLh+QtLdH6R2eAjvBuA+SDIy7YznR7BKW3EizmqH6VN+MsxB uxey41YMpJnvhKKyc8zjy45BNFj8ocAEVyyrFUWdoJ1l37rTWYq3qzubhJCLfNAH3S ox6lS2KEQz/6g== Message-ID: Date: Fri, 26 Jun 2026 21:50:11 +0200 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH splitout] mm: memory-failure: serialize TestSetPageHWPoison with zone->lock To: "Michael S. Tsirkin" Cc: Miaohe Lin , Zi Yan , Andrew Morton , linux-kernel@vger.kernel.org, Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Muchun Song , Oscar Salvador , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli , Naoya Horiguchi References: <14537566-94d9-eac5-2636-35f925a9d159@huawei.com> <20260611013644-mutt-send-email-mst@kernel.org> <1b5676ab-0dc5-ef33-9d79-a2bd6090a62d@huawei.com> <984d9775-e17c-0231-b021-126b13a9aa42@huawei.com> <438389f2-332d-2f70-cad4-784d7f54af9f@huawei.com> <20260616161353-mutt-send-email-mst@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: <20260616161353-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/16/26 23:35, Michael S. Tsirkin wrote: > On Tue, Jun 16, 2026 at 02:18:57PM +0200, David Hildenbrand (Arm) wrote: >> On 6/16/26 13:40, Miaohe Lin wrote: >>> >>> I scanned the code and found rcu_read_unlock_special might be called in some cases. >>> Some expensive ops, e.g. irq_work_queue_on, might be called in some corner cases. >>> So the overhead of rcu read lock might be fluctuating. >> >> Right. Usually rcu_read_lock+unlock is supposed to be very lightweight, but that >> might not be completely the case with that PREEMPT_RCU thingy ... >> >>> >>> >>> Sure. We can do that if needed. >>> >>> >>> Right. hypervisor could make the issue easier to trigger... >>> >>> >>> I think your proposal, although there are still some issues to be resolved, is >>> nevertheless a good solution. We could also wait and see if anyone comes up with >>> a better one. >> >> I wouldn't call it "good" ... it's the only thing I was easily able to come up >> with :) >> >> The only alternative would be moving the hwpoison bit out of page->flags, >> storing it in a sparse bitmap or sth. like that. It would be a bigger rework and >> I am sure there are issues with that as well. >> >> -- >> Cheers, >> >> David > > > I had a vague feeling using static keys should be possible somehow, > but could not come up with anything robust. I skimmed over it, but concluded that it's worse than what I envisioned. (e.g., two rcu read lock+unlock over consecutive updates). It's also doesn't address the mf_mutex implications and the x86 thingies I mentioned. The rcu_is_watching() optimization is interesting, wonder though if that is really relevant in practice. I'll either take care of that myself or find someone that can work on this with attention to all details. -- Cheers, David