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Memory sections are combined into "memory block" chunks. These chunks are the units upon which memory can be added and removed. On x86, the new memory may be added after the end of the boot memory, therefore, if block size does not align with end of boot memory, memory hot-plugging/hot-removing can be broken. Memory sections are combined into "memory block" chunks. These chunks are the units upon which memory can be added and removed. On x86 the new memory may be added after the end of the boot memory, therefore, if block size does not align with end of boot memory, memory hotplugging/hotremoving can be broken. Currently, whenever machine is booted with more than 64G the block size is unconditionally increased to 2G from the base 128M. This is done in order to reduce number of memory device files in sysfs: /sys/devices/system/memory/memoryXXX We must use the largest allowed block size that aligns to the next address to be able to hotplug the next block of memory. So, when memory is larger or equal to 64G, we check the end address and find the largest block size that is still power of two but smaller or equal to 2G. Before, the fix: Run qemu with: -m 64G,slots=2,maxmem=66G -object memory-backend-ram,id=mem1,size=2G (qemu) device_add pc-dimm,id=dimm1,memdev=mem1 Block size [0x80000000] unaligned hotplug range: start 0x1040000000, size 0x80000000 acpi PNP0C80:00: add_memory failed acpi PNP0C80:00: acpi_memory_enable_device() error acpi PNP0C80:00: Enumeration failure With the fix memory is added successfully as the block size is set to 1G, and therefore aligns with start address 0x1040000000. [pasha.tatashin@oracle.com: v4] Link: http://lkml.kernel.org/r/20180215165920.8570-3-pasha.tatashin@oracle.com Link: http://lkml.kernel.org/r/20180213193159.14606-3-pasha.tatashin@oracle.com Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Sistare <steven.sistare@oracle.com> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@suse.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Bharata B Rao <bharata@linux.vnet.ibm.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Baoquan He <bhe@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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