From: "Huang, Ying" <ying.huang@linux.alibaba.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: David Hildenbrand <david@redhat.com>,
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 [thread overview]
Message-ID: <87cy9j1pol.fsf@DESKTOP-5N7EMDA> (raw)
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
reply other threads:[~2025-07-29 6:25 UTC|newest]
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