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 C30CBC43458 for ; Wed, 1 Jul 2026 08:26:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9C9706B00A6; Wed, 1 Jul 2026 04:26:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 97A496B00A8; Wed, 1 Jul 2026 04:26:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 841C46B00A9; Wed, 1 Jul 2026 04:26:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 5A4F46B00A6 for ; Wed, 1 Jul 2026 04:26:38 -0400 (EDT) Received: from smtpin19.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id E1C1D1A02AA for ; Wed, 1 Jul 2026 08:26:37 +0000 (UTC) X-FDA: 84939526434.19.29F2477 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf22.hostedemail.com (Postfix) with ESMTP id 0E481C000B for ; Wed, 1 Jul 2026 08:26:35 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=O3Z7BMXD; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf22.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782894396; b=cF+1ClDvOm/+bN8lKxFa/VJx03SjiO+rRXMCjUhkbE5StG5sGOpe+RrDPe2jrOEnbDdnzN zNX+/KH2mX2jGjUOd4nJyE3q0uxoywVAHqSGZm+6zMJ7v9B2uh09PW5is4MZCus/gxQ0Df +FR1IAHt3Ezr3zjTeRH56I2WgPaIyfI= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782894396; 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=+T+6J6rF16tlV8s9JGhRswkVJRz4ywliNTiQ4lmmWRg=; b=zAf9ofY3bF9U7xG0B2jQ5u9ylwGxIYpJ4r6UBQJ9VXRx9pW9gLfFro7z/jcR9zq9AM2+py xz6CP1sO0Ff2afDhrJnyXOfM6gWbpEYB7TjFd0Q1ycL9k1X50p6n0HD/SvSnDkHn9vzSgn Bxw6M9syvLQJ9QjfT4/fWpPwreMc60U= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=O3Z7BMXD; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf22.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 38D4643356; Wed, 1 Jul 2026 08:26:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8569F1F00A3D; Wed, 1 Jul 2026 08:26:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782894395; bh=+T+6J6rF16tlV8s9JGhRswkVJRz4ywliNTiQ4lmmWRg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=O3Z7BMXD/3eyk+k/b4yeYELZ1QysIsroVxIbhrZy8ce8eHAFukhtRLDsgY2+iPhy2 Fwhrf5+Cpin6juYgi7dSgn5vPHWFXIq8NmZOOeGOR8XkuWJChLFiNjG+8xtb/bpuit cZ/O39SiQykRMytVEDFPLz6LBZLoKYhB59d8FOgLY8TdAi9vLnWIC/sqqZVNT5DuIe PiVhwssdVaT7lfDToXrHQW2KbU0rge7a1y//tJtWiFGxGlPQU31sW4fDOQt3AX46XJ lkmeS1LpVJWaWSXro1KZXp7c1OqEHtqKB8ImYlY3YDgV9TFXCevaxMIe5bPL440PQi VsFRQVqZUeGZw== Message-ID: Date: Wed, 1 Jul 2026 10:26:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] mm: memory-failure: fix HWPoison flag race with non-atomic page flag ops To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Miaohe Lin , Naoya Horiguchi , Andrew Morton , Oscar Salvador , Andi Kleen , Hidehiro Kawai , Rik van Riel , Vlastimil Babka , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Hao Li , Kiryl Shutsemau , Byungchul Park , linux-mm@kvack.org, linux-cxl@vger.kernel.org References: <0b5f8b4b-d7dc-4b79-9555-a5b36265f3a9@kernel.org> <20260629030657-mutt-send-email-mst@kernel.org> <4f5ba5d6-246c-4430-9737-e8dd8e4c5142@kernel.org> <20260629092856-mutt-send-email-mst@kernel.org> <54c8cbee-9b26-458c-93ba-5aa594f5d1e8@kernel.org> <20260629174225-mutt-send-email-mst@kernel.org> <20260630174852-mutt-send-email-mst@kernel.org> <2f884bfa-3cd5-4fba-8aa4-c2e68890ab64@kernel.org> <20260701041112-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: <20260701041112-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0E481C000B X-Stat-Signature: fg1qqc6pu5yc7s8fbete9utmmfoysbe7 X-HE-Tag: 1782894395-93397 X-HE-Meta: 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 tnlEOQgw xS+2XzjT5PX1O6h/EkAmXp1ykvPzycdkaozbT7ojSWuLmykrV3lFihSLIMyP5sIC1Hc4yNkHvvjCeQKRDcX8Ievfoky4WUAEbMODh79LchtKnWmbhuPl/+OLASlviEdf+HHE5QS49g8DdJ8bvYVe4OLL3Mbc3SfRALhImE2YT94aXgjP9x7LZxH5gRKu11LD+qMgOudzagcTwq7m1F3hJ/ze2cV9P/DmqE9C6iF0T7D1sdaU8HRVKlFXi+OPjQ9vRCZBU5Qo6tToLh/LotpUc/UeoSibD12LdTLAhxY5M2JosUrmvy9H2pJWpSJeu+8uWrgD5Go908bb/SkOrHDwaGlLlrg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/1/26 10:18, Michael S. Tsirkin wrote: > On Wed, Jul 01, 2026 at 10:08:45AM +0200, David Hildenbrand (Arm) wrote: >>> >>> Yay. I did that + dropped the extra lock/unlock and now it's in the noise in >>> my testing. needs much more testing of course. >> >> Cool. I'd expect that latency-sensitive workloads (PREEMPT_RT) would not want to >> have hwpoison handling either way, so using the no_resched variants at these >> places might be doable. >> >>> >>> If you want me to post (including addressing your other feedback) let me >>> know. >>> >> >> Let's first discuss the options. We essentially have the following one so far: >> >> 1) Ignore the problem >> >> It's been there forever ... but I am not quite happy about that. >> >> 2) Use atomics everywhere >> >> The easiest+cleanest, but as measured, the performance hit is real. >> >> 3) Keep retrying for a couple of times >> >> The big problem is "how long". A CPU in a hypervisor might be stalled for quite >> a while (20s? can be longer). > > So on this idea. It might not matter. What I had in mind is: > 1. run the current logic > 2. add page to a list of pages to check, then invoke e.g. call_rcu_tasks > (or call_rcu_tasks_rude) maybe > 3. in the callback, recheck and if poison cleared, go back to 1 > 4. otherwise everyone will see the bit set, remove from list we are done > > it seems to not regress anything, and for the rare race, we set > the bit eventually. > So test-and-set (and friends) would also have to check the data structure that remembers bit to set/clear (and possibly update the data structure). That does seem doable. Do you have a prototype? -- Cheers, David