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]) by smtp.lore.kernel.org (Postfix) with ESMTP id BB280C87FC9 for ; Tue, 29 Jul 2025 06:23:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 358426B007B; Tue, 29 Jul 2025 02:23:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 309C56B0089; Tue, 29 Jul 2025 02:23:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 21EC46B008A; Tue, 29 Jul 2025 02:23:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 12D096B007B for ; Tue, 29 Jul 2025 02:23:00 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 86A5659386 for ; Tue, 29 Jul 2025 06:22:59 +0000 (UTC) X-FDA: 83716309278.21.E441167 Received: from out30-111.freemail.mail.aliyun.com (out30-111.freemail.mail.aliyun.com [115.124.30.111]) by imf24.hostedemail.com (Postfix) with ESMTP id 67470180006 for ; Tue, 29 Jul 2025 06:22:56 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=PCDwXUNu; dmarc=pass (policy=none) header.from=linux.alibaba.com; spf=pass (imf24.hostedemail.com: domain of ying.huang@linux.alibaba.com designates 115.124.30.111 as permitted sender) smtp.mailfrom=ying.huang@linux.alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1753770177; a=rsa-sha256; cv=none; b=d/K0LrziQ3JVfHjUdlGsUgu0FoEREOc1dytCmhLgjCWmE5aP9XXSoXkUY00cjySduxzTqI DrncbvMo6JfcqKuvX/fZTMTGXdgA1XPyNvn1br60dsHS9Wp2rQfwTTMcaUvjkAVcytsDFR 5+zTJ+KqFHao62NfoiMljEVuqNzbll8= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=PCDwXUNu; dmarc=pass (policy=none) header.from=linux.alibaba.com; spf=pass (imf24.hostedemail.com: domain of ying.huang@linux.alibaba.com designates 115.124.30.111 as permitted sender) smtp.mailfrom=ying.huang@linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1753770177; 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:in-reply-to: references:dkim-signature; bh=F2yOpyt/YqjoKcmqvqIBEL8aDBHvJPFc1AXuZ7tPAYg=; b=L+2UvjraI9OILIiHUE8fymidvkrD2cjcnP4+5ve4vNqZ+5EGS27rfD4irYtVxpqD6RfN1b bbOnnSOCAIq6wVSVHnv8Z6DKQ3Lr3ZMB14v6DImVpiKnhRPuob5lLl5rPilx59Guz8bL07 EoS28Y42y59Kf59+ltJrxKxIocEsgt4= DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1753770173; h=From:To:Subject:Date:Message-ID:MIME-Version:Content-Type; bh=F2yOpyt/YqjoKcmqvqIBEL8aDBHvJPFc1AXuZ7tPAYg=; b=PCDwXUNuJ5Nw2d50dCN8NkikB1hqrah/VJ1DXFkXpbh+BpoNXdnkzluxCjqLyWw0pvHKvTUDXhgMSwKFplEiyLmW/Y2wwPD41olbONx5fz1h6ACRBw3rgvlY0jZYp1jTsZ3RRecQFGoGMlROymFhH/UkXWjQnp2XV1nOS8WH7dA= Received: from DESKTOP-5N7EMDA(mailfrom:ying.huang@linux.alibaba.com fp:SMTPD_---0WkP.haK_1753770170 cluster:ay36) by smtp.aliyun-inc.com; Tue, 29 Jul 2025 14:22:51 +0800 From: "Huang, Ying" To: Anshuman Khandual Cc: David Hildenbrand , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org Subject: Why prevent boot memory to be hot-removed on arm64? Date: Tue, 29 Jul 2025 14:22:50 +0800 Message-ID: <87cy9j1pol.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 67470180006 X-Stat-Signature: 6aqnn9wxdbrroacy3hw99qguoa7mf9xw X-Rspam-User: X-HE-Tag: 1753770176-434221 X-HE-Meta: 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 nUn9RWW6 c+FGFuHs3uhqft2swpBaSDtg8AcPs4jijBc4eatZENuaWZkLUEPnFlLl+tkdmN8+PQmJDv380Xj+1P+KeRp+ck+l9NID+hBH2BaPRpE4lHEKQZHcuUkkpemcOZQfkXcv77TyWBieuda+asPGLvRnYOo89tMx9zDT7ZOOJuV1gtJEI+a+3YUct2LwjeZvgSEtS1ZAck+oqX9jDL0ENQI1ugZ0TYz59G2BlcrN2m4/kU7+4z1FXsPBvOTe8B6aVa5EbYMrgw3Ssle/ffOv18oZFT7KCLqQuYBHeXSJiIgBymoyWiWq1rLl4WwZMoA== 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: Hi, Anshuman, When I read memory hotplug code on arm64, I found that a memory notifier (prevent_bootmem_remove_notifier()) is used to prevent the boot memory to be hot-removed on arm64. I understand that some memory (for example the boot memory) shouldn't be hot-removed on some platforms. However, after checking the code, I found that the memory can only be hot-removed via ACPI (acpi_memory_device_remove()), CXL/NVDIMM (dev_dax_kmem_remove()), or virtio mem (virtio_mem_remove_memory). IIUC, CXL/NVDIMM or virtio mem shouldn't be boot memory, and ACPI memory hot-remove shouldn't be setup by the firmware if some memory ranges shouldn't be hot-removed. If so, the boot memory cannot be hot-removed accidentally, prevent_bootmem_remove_notifier() just makes the boot memory can not be offlined. Or I missed something? --- Best Regards, Huang, Ying