Messages in this thread | | | Date | Wed, 21 Nov 2012 10:25:58 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86, smpboot: allow manual hotplug of CPUs |
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On 11/21/2012 10:22 AM, Sasha Levin wrote: > So far CPU hotplug was ignored for mptable implementations which support it by > having the hotpluggable CPUs marked as disabled during boot. > > The current kernel code detects that behaviour and actually deals with it > properly: > > [ 0.000000] Intel MultiProcessor Specification v1.4 > [ 0.000000] MPTABLE: OEM ID: KVMCPU00 > [ 0.000000] MPTABLE: Product ID: 0.1 > [ 0.000000] MPTABLE: APIC at: 0xFEE00000 > [ 0.000000] Processor #0 (Bootup-CPU) > [ 0.000000] Processor #1 > [ 0.000000] Processor #2 > [ 0.000000] IOAPIC[0]: apic_id 4, version 17, address 0xfec00000, GSI 0-23 > [ 0.000000] Processors: 3 > [ 0.000000] smpboot: Allowing 3 CPUs, 1 hotplug CPUs > > The problem begins when a user might actually want to online such CPU; there > is no interface for him to tell the kernel that the CPU is now present and > can be used. > > Luckily, the kernel provides a generic interface in the form of 'probe' and > 'release' sysfs files which are used on different architectures exactly for > that - to probe and release CPUs. On x86 however this was unimplemented > until now. > > This patch adds code into the x86 implementation of probe and release to allow > adding and removing CPUs. This allows machines that use mptable to hotplug > CPUs: >
Reading between the lines, this sounds like would cause a user-visible difference between mptable platforms and ACPI platforms? If so, that is totally unacceptable. If not, the description is confusing.
-hpa
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