diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-07-14 13:43:24 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-07-14 13:43:24 -0700 |
| commit | a3da5bf84a97d48cfaf66c6842470fc403da5121 (patch) | |
| tree | cdf66c0cff8c61eedd60601fc9dffdd1ed39b880 /Documentation/x86/x86_64/cpu-hotplug-spec | |
| parent | 3b23e665b68387f5ee7b21f7b75ceea4d9acae4a (diff) | |
| parent | d59fdcf2ac501de99c3dfb452af5e254d4342886 (diff) | |
Merge branch 'x86/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'x86/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (821 commits)
x86: make 64bit hpet_set_mapping to use ioremap too, v2
x86: get x86_phys_bits early
x86: max_low_pfn_mapped fix #4
x86: change _node_to_cpumask_ptr to return const ptr
x86: I/O APIC: remove an IRQ2-mask hack
x86: fix numaq_tsc_disable calling
x86, e820: remove end_user_pfn
x86: max_low_pfn_mapped fix, #3
x86: max_low_pfn_mapped fix, #2
x86: max_low_pfn_mapped fix, #1
x86_64: fix delayed signals
x86: remove conflicting nx6325 and nx6125 quirks
x86: Recover timer_ack lost in the merge of the NMI watchdog
x86: I/O APIC: Never configure IRQ2
x86: L-APIC: Always fully configure IRQ0
x86: L-APIC: Set IRQ0 as edge-triggered
x86: merge dwarf2 headers
x86: use AS_CFI instead of UNWIND_INFO
x86: use ignore macro instead of hash comment
x86: use matching CFI_ENDPROC
...
Diffstat (limited to 'Documentation/x86/x86_64/cpu-hotplug-spec')
| -rw-r--r-- | Documentation/x86/x86_64/cpu-hotplug-spec | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/x86/x86_64/cpu-hotplug-spec b/Documentation/x86/x86_64/cpu-hotplug-spec new file mode 100644 index 000000000000..3c23e0587db3 --- /dev/null +++ b/Documentation/x86/x86_64/cpu-hotplug-spec @@ -0,0 +1,21 @@ +Firmware support for CPU hotplug under Linux/x86-64 +--------------------------------------------------- + +Linux/x86-64 supports CPU hotplug now. For various reasons Linux wants to +know in advance of boot time the maximum number of CPUs that could be plugged +into the system. ACPI 3.0 currently has no official way to supply +this information from the firmware to the operating system. + +In ACPI each CPU needs an LAPIC object in the MADT table (5.2.11.5 in the +ACPI 3.0 specification). ACPI already has the concept of disabled LAPIC +objects by setting the Enabled bit in the LAPIC object to zero. + +For CPU hotplug Linux/x86-64 expects now that any possible future hotpluggable +CPU is already available in the MADT. If the CPU is not available yet +it should have its LAPIC Enabled bit set to 0. Linux will use the number +of disabled LAPICs to compute the maximum number of future CPUs. + +In the worst case the user can overwrite this choice using a command line +option (additional_cpus=...), but it is recommended to supply the correct +number (or a reasonable approximation of it, with erring towards more not less) +in the MADT to avoid manual configuration. |