From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 4C4AD33CE9B for ; Thu, 16 Oct 2025 10:47:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760611624; cv=none; b=hD4p+v+BV+kJwjn45YiKLZSrKsQcXnkfVwMSdy6b29Wm261vNQXjirUVQRHHwaqRuLUZBZKjFBVy0Q/9N0Q4EL9O2ZDEP7M8tcGQ5tfUdWisLT9Fy4XxTHNhXE1nSMxtItG8k8FvJG18yR6LCpPo7n3fpKAIzv+7gKu0BU7mnFs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760611624; c=relaxed/simple; bh=a5BbmQEbWc8yZ4ZNc6ZCQ4vjuI1iaJYdkMNyGW0QmU0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NibUwqRmuiPRBdScddcT2IfxHRnSSLWgWNhcHwfPTnB8AhhX/6bduqX7ZoyJlyhxFPtumwPRp3NsqHmgiSE0AtgcznDxYusXwvykTTBPhLAePOrF0Gq4LT68zAmfWOT/80Koy6kZxtTy+Fx0xF6BnZwizPCcMVfR24b1a625omM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=TuTasb8Z; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TuTasb8Z" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760611620; 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=PWC1fBf3NN4ANTq+x7IzYDPSJqt6PESsXElpj8+2ZTI=; b=TuTasb8ZzDAF0hIjcvb9DNbX5DUpgnVlahqExJwqoUFui31Y3t0J2tQmewy07JOgX8DdRf tsQV2+K1AA3eLyfKrybAe2HYCKVKjLfkHwY7Cgbn5Y2vxWmwUBjac3X/2wMv7iYJoV+7gc GJv9nnIbRq6lOm9JHVjVqygVm+7lk00= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-245-2NbW9JvmNG2Y58U1KurFng-1; Thu, 16 Oct 2025 06:46:58 -0400 X-MC-Unique: 2NbW9JvmNG2Y58U1KurFng-1 X-Mimecast-MFC-AGG-ID: 2NbW9JvmNG2Y58U1KurFng_1760611618 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-471168953bdso217145e9.1 for ; Thu, 16 Oct 2025 03:46:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760611617; x=1761216417; 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=PWC1fBf3NN4ANTq+x7IzYDPSJqt6PESsXElpj8+2ZTI=; b=qbvOYDxa3fwYjd4MNAB5UHIdHvGCX3EnPjCa0UrmconPUQGNEuDFVXlOkHxZ8GBeXM Ess/K4zwK6SwTalmikDLPBTfESAt6hWwtM/yRaRmnZyTV2WJXD1hIo7ctzWtgzEa8wBs IjGbMsfGfC0KJxINbnN3q6LzlqbqjzBFqx1tEAmOhiXQVXHoKqHWMx4v0Cqmz7sCiO7G PraiXvdnK+oJosYhgBmeUJVrOARH73wReH2FEawmg9dOtUF2+8RSM/1mGsykAfgvrljM Yfxqmov29asWoyyVqJdAsJs62cHs1C0WDWjnYT6vmVfModEVYKtroWp5YVXpMuUK82v9 dIdA== X-Forwarded-Encrypted: i=1; AJvYcCV71kF0fIshm3o7unibpD2rf0Lm23xsGUWLOdEhZK4mMIPwZiIk+kJbju9/YAQo5od44iDevsJy/EnQ6rI=@vger.kernel.org X-Gm-Message-State: AOJu0YxrwmXzv1dQZxqDhfGDE5Gkv+h9F79TGY79uKS7I76yXRcAwfE/ zXfW9jo5iCM6y4E5FJOsF4h4nwjuO2QA8OyMvrpCrrYWbwxiF3qOyoGoF2eP0oYA64FbHglQlHE Bi6B9S7qGt+HzgTkfiGjOKutIqgVxiHH2sZprIzr6XoXWQqmtt5c3KLcttLuvwStrZA== X-Gm-Gg: ASbGnctXV9zspabcjdpUjyxcNrUo7P7GlDfwtIhInp1WppUnF51+4setrL91cdmB2+B TNDQ0OSvbi17BBchkoHCGe0UoK59HH6Wn/EfEsIPbtVlrtt7UIxtZMkKed5jdcIR4LTqhJHf1MI 6rHLxVXVMbqyRFJi9XQo2w/vsMyATSCo+K7lV4C0+HGqQmSSaITCQ3C/pVJ8D+sX4tvjD45lmOv iT1pewQ3NiayVVJMZfT3j1hwaq7Htin2NwXurDOD36LhWsnEnDmg5/Za+GsYADgH6vERet5mNPt IjPYJsQYs/m/pQFwy+qaLSCoRkbdyyoMFytFbbvk+UtxOgSGM0QMyCQpJxLH3tOvfI7bhS3f52X oCqZrBM2Ty3jWyr/ovBEa7W0nF7tLVNBRZ9BsryQTwq+G3pwJJsy5JxfAIYS/Ya+sNIN2o3w9is 6Vt/UNHVn/JaEMCYpId0dU7Od2hBI= X-Received: by 2002:a05:600c:64ce:b0:46d:1a9b:6d35 with SMTP id 5b1f17b1804b1-47109b2838emr22729075e9.14.1760611617504; Thu, 16 Oct 2025 03:46:57 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEeVBgV9jTy2rMK7hSPUVLMGqdGDRZexkRhARKgF/fANx4xtmRQVfCaL0Mp8w2hsw9kLHDcCw== X-Received: by 2002:a05:600c:64ce:b0:46d:1a9b:6d35 with SMTP id 5b1f17b1804b1-47109b2838emr22728865e9.14.1760611617023; Thu, 16 Oct 2025 03:46:57 -0700 (PDT) Received: from ?IPV6:2003:d8:2f0c:c200:fa4a:c4ff:1b32:21ce? (p200300d82f0cc200fa4ac4ff1b3221ce.dip0.t-ipconnect.de. [2003:d8:2f0c:c200:fa4a:c4ff:1b32:21ce]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-471144b5c29sm18829355e9.12.2025.10.16.03.46.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Oct 2025 03:46:56 -0700 (PDT) Message-ID: <7e533422-1707-4fea-9350-0e832cf24a83@redhat.com> Date: Thu, 16 Oct 2025 12:46:55 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/1] mm/ksm: recover from memory failure on KSM page by migrating to healthy duplicate To: Longlong Xia , linmiaohe@huawei.com, lance.yang@linux.dev Cc: markus.elfring@web.de, nao.horiguchi@gmail.com, akpm@linux-foundation.org, wangkefeng.wang@huawei.com, qiuxu.zhuo@intel.com, xu.xin16@zte.com.cn, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20251016101813.484565-1-xialonglong2025@163.com> From: David Hildenbrand Content-Language: en-US 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: <20251016101813.484565-1-xialonglong2025@163.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 16.10.25 12:18, Longlong Xia wrote: > When a hardware memory error occurs on a KSM page, the current > behavior is to kill all processes mapping that page. This can > be overly aggressive when KSM has multiple duplicate pages in > a chain where other duplicates are still healthy. > > This patch introduces a recovery mechanism that attempts to > migrate mappings from the failing KSM page to a newly > allocated KSM page or another healthy duplicate already > present in the same chain, before falling back to the > process-killing procedure. > > The recovery process works as follows: > 1. Identify if the failing KSM page belongs to a stable node chain. > 2. Locate a healthy duplicate KSM page within the same chain. > 3. For each process mapping the failing page: > a. Attempt to allocate a new KSM page copy from healthy duplicate > KSM page. If successful, migrate the mapping to this new KSM page. > b. If allocation fails, migrate the mapping to the existing healthy > duplicate KSM page. > 4. If all migrations succeed, remove the failing KSM page from the chain. > 5. Only if recovery fails (e.g., no healthy duplicate found or migration > error) does the kernel fall back to killing the affected processes. > > The original idea came from Naoya Horiguchi. > https://lore.kernel.org/all/20230331054243.GB1435482@hori.linux.bs1.fc.nec.co.jp/ > > I test it with einj in physical machine x86_64 CPU Intel(R) Xeon(R) Gold 6430. > > test shell script > modprobe einj 2>/dev/null > echo 0x10 > /sys/kernel/debug/apei/einj/error_type > echo $ADDRESS > /sys/kernel/debug/apei/einj/param1 > echo 0xfffffffffffff000 > /sys/kernel/debug/apei/einj/param2 > echo 1 > /sys/kernel/debug/apei/einj/error_inject > > FIRST WAY: allocate a new KSM page copy from healthy duplicate > 1. alloc 1024 page with same content and enable KSM to merge > after merge (same phy_addr only print once) > virtual addr = 0x71582be00000 phy_addr =0x124802000 > virtual addr = 0x71582bf2c000 phy_addr =0x124902000 > virtual addr = 0x71582c026000 phy_addr =0x125402000 > virtual addr = 0x71582c120000 phy_addr =0x125502000 > > > 2. echo 0x124802000 > /sys/kernel/debug/apei/einj/param1 > virtual addr = 0x71582be00000 phy_addr =0x1363b1000 (new allocated) > virtual addr = 0x71582bf2c000 phy_addr =0x124902000 > virtual addr = 0x71582c026000 phy_addr =0x125402000 > virtual addr = 0x71582c120000 phy_addr =0x125502000 > > > 3. echo 0x124902000 > /sys/kernel/debug/apei/einj/param1 > virtual addr = 0x71582be00000 phy_addr =0x1363b1000 > virtual addr = 0x71582bf2c000 phy_addr =0x13099a000 (new allocated) > virtual addr = 0x71582c026000 phy_addr =0x125402000 > virtual addr = 0x71582c120000 phy_addr =0x125502000 > > kernel-log: > mce: [Hardware Error]: Machine check events logged > ksm: recovery successful, no need to kill processes > Memory failure: 0x124802: recovery action for dirty LRU page: Recovered > Memory failure: 0x124802: recovery action for already poisoned page: Failed > ksm: recovery successful, no need to kill processes > Memory failure: 0x124902: recovery action for dirty LRU page: Recovered > Memory failure: 0x124902: recovery action for already poisoned page: Failed > > > SECOND WAY: Migrate the mapping to the existing healthy duplicate KSM page > 1. alloc 1024 page with same content and enable KSM to merge > after merge (same phy_addr only print once) > virtual addr = 0x79a172000000 phy_addr =0x141802000 > virtual addr = 0x79a17212c000 phy_addr =0x141902000 > virtual addr = 0x79a172226000 phy_addr =0x13cc02000 > virtual addr = 0x79a172320000 phy_addr =0x13cd02000 > > 2 echo 0x141802000 > /sys/kernel/debug/apei/einj/param1 > a.virtual addr = 0x79a172000000 phy_addr =0x13cd02000 > b.virtual addr = 0x79a17212c000 phy_addr =0x141902000 > c.virtual addr = 0x79a172226000 phy_addr =0x13cc02000 > d.virtual addr = 0x79a172320000 phy_addr =0x13cd02000 (share with a) > > 3.echo 0x141902000 > /sys/kernel/debug/apei/einj/param1 > a.virtual addr = 0x79a172000000 phy_addr =0x13cd02000 > b.virtual addr = 0x79a172032000 phy_addr =0x13cd02000 (share with a) > c.virtual addr = 0x79a172226000 phy_addr =0x13cc02000 > d.virtual addr = 0x79a172320000 phy_addr =0x13cd02000 (share with a) > > 4. echo 0x13cd02000 > /sys/kernel/debug/apei/einj/param1 > a.virtual addr = 0x79a172000000 phy_addr =0x13cc02000 > b.virtual addr = 0x79a172032000 phy_addr =0x13cc02000 (share with a) > c.virtual addr = 0x79a172226000 phy_addr =0x13cc02000 (share with a) > d.virtual addr = 0x79a172320000 phy_addr =0x13cc02000 (share with a) > > 5. echo 0x13cc02000 > /sys/kernel/debug/apei/einj/param1 > Bus error (core dumped) > > kernel-log: > mce: [Hardware Error]: Machine check events logged > ksm: recovery successful, no need to kill processes > Memory failure: 0x141802: recovery action for dirty LRU page: Recovered > Memory failure: 0x141802: recovery action for already poisoned page: Failed > ksm: recovery successful, no need to kill processes > Memory failure: 0x141902: recovery action for dirty LRU page: Recovered > Memory failure: 0x141902: recovery action for already poisoned page: Failed > ksm: recovery successful, no need to kill processes > Memory failure: 0x13cd02: recovery action for dirty LRU page: Recovered > Memory failure: 0x13cd02: recovery action for already poisoned page: Failed > Memory failure: 0x13cc02: recovery action for dirty LRU page: Recovered > Memory failure: 0x13cc02: recovery action for already poisoned page: Failed > MCE: Killing ksm_addr:5221 due to hardware memory corruption fault at 79a172000000 > > ZERO PAGE TEST: > when I test in physical machine x86_64 CPU Intel(R) Xeon(R) Gold 6430 > [shell]# ./einj.sh 0x193f908000 > ./einj.sh: line 25: echo: write error: Address already in use > > when I test in qemu-x86_64. > Injecting memory failure at pfn 0x3a9d0c > Memory failure: 0x3a9d0c: unhandlable page. > Memory failure: 0x3a9d0c: recovery action for get hwpoison page: Ignored > > It seems return early before enter this patch's functions. > > Thanks for review and comments! > > Changes in v2: > > - Implemented a two-tier recovery strategy: preferring newly allocated > pages over existing duplicates to avoid concentrating mappings on a > single page suggested by David Hildenbrand I also asked how relevant this is in practice [1] " But how realistic do we consider that in practice? We need quite a bunch of processes to dedup the same page to end up getting duplicates in the chain IIRC. So isn't this rather an improvement only for less likely scenarios in practice? " In particular for your test "alloc 1024 page with same content". It certainly adds complexity, so we should clarify if this is really worth it. [1] https://lore.kernel.org/all/8c4d8ebe-885e-40f0-a10e-7290067c7b96@redhat.com/ -- Cheers David / dhildenb