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Tue, 4 Nov 2025 21:31:30 +0800 (CST) Received: from kwepemj100009.china.huawei.com (unknown [7.202.194.3]) by mail.maildlp.com (Postfix) with ESMTPS id 703D41402F2; Tue, 4 Nov 2025 21:32:59 +0800 (CST) Received: from DESKTOP-A37P9LK.huawei.com (10.67.109.17) by kwepemj100009.china.huawei.com (7.202.194.3) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 4 Nov 2025 21:32:58 +0800 From: Xie Yuanbin To: , , , , , , , , , , , , , , , , , , CC: , , , , , , , Xie Yuanbin Subject: Re: [PATCH v2 0/2] x86/mm: support memory-failure on 32-bits with SPARSEMEM Date: Tue, 4 Nov 2025 21:32:54 +0800 Message-ID: <20251104133254.145660-1-xieyuanbin1@huawei.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <1b316667-470b-4e1a-9c18-e42571e4769c@kernel.org> References: <1b316667-470b-4e1a-9c18-e42571e4769c@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.67.109.17] X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemj100009.china.huawei.com (7.202.194.3) X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: BE8198000C X-Stat-Signature: y37ohfsm6yoe4pemunebw4i8yegbo5rs X-Rspam-User: X-HE-Tag: 1762263186-707286 X-HE-Meta: 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 ZykD1k3H dvsr6AspNM1vBQhTBrYPVhsu4bgSKc9anGYgQk6RzFgprPUPyBN4tZSNcTrFpcjWA9gLTUqAIQ/tJUyfW7ptqELyv2NDyvJdPzxX0b35VBsBtt7aGP00tP9ncWF/5uxYb5DUeC+WVUsB6SFCcu3P6LErRn4mFC9wtMBWKd8Ou/fNLTGYn11oyV7k0U2M7Vwrkvo5DAke1LJko6zonB1a1imWm/+q4Pte3e/Y82Qfx95NHXPaHgUHuyxDiCKwooz1gKFSwjMRoQUSgyjzcNBxw8yTtjgwSWEJnrAFpyNGV8vyHgBCfx4deMYx9URli9fiYWDQPxsBVg00Vl3TKEY3bTofdgg== 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: The previous email was corrupted; please ignore it. I'm very sorry about this. On Tue, 4 Nov 2025 10:33:39 +0100, David Hildenbrand wrote: > This is a pretty generic description of MCEs. > > I think what we are missing is: who runs 32bit OSes on MCE-capable > hardware (or VMs?) and needs this to work. > > What's the use case? I did indeed miss this part in my description, and I apologize for that. Since the memory-failure feature was introduced, from commit 6a46079cf57a7f7758e8 ("HWPOISON: The high level memory error handler in the VM v7"), it can be enabled on x86_32, submitting these patches only because MEMORY_FAILURE cannot be enabled together with SPARSEMEM on x86_32. The memory-failure was introduced in 2009, when 64-bit hardware was not even very popular yet, and the first caller of `memory_failure()` is from x86's MCE. Even in latest version, with default i386_defconfig, MEMORY_FAILURE can be enabled directly on x86_32, because i386_defconfig does not enable SPARSEMEM by default. Therefore, I did not consider the need to explain why MEMORY_FAILURE needs to be enabled on the x86_32. Now, let me try to explain it. From what I understand, it mainly comes from two aspects: 1. Although almost all new CPUs are 64-bit, there are still many existing 32-bit x86 devices in uses. 2. On some embedded devices, in order to save memory overhead, even with 64-bit CPU hardware, a 32-bit kernel may still be used. You might wonder why embedded devices need SPARSEMEM. This is because the MEMORY_HOTPLUG feature depends on SPARSEMEM, not necessarily SPARSEMEM itself. All of the above devices, the memory-failure feature may be used to provide reliable memory errors handling, and to minimize service interruptions as much as possible. > Cheers > > David Thanks! Xie Yuanbin