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author | Ben Dooks <ben-linux@fluff.org> | 2008-07-15 20:19:14 +0100 |
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committer | Ben Dooks <ben-linux@fluff.org> | 2008-07-15 20:19:14 +0100 |
commit | 0c17e4ceedd35c78b1c7413dbd16279a350be6bc (patch) | |
tree | 313b3b9ca04727f3704464e01d8dd97da1dd534b /Documentation/x86/x86_64/cpu-hotplug-spec | |
parent | 19c1d6a34abf73d0baf8e325d018c920fa78dddc (diff) | |
parent | b9d2252c1e44fa83a4e65fdc9eb93db6297c55af (diff) | |
download | kernel_samsung_smdk4412-0c17e4ceedd35c78b1c7413dbd16279a350be6bc.zip kernel_samsung_smdk4412-0c17e4ceedd35c78b1c7413dbd16279a350be6bc.tar.gz kernel_samsung_smdk4412-0c17e4ceedd35c78b1c7413dbd16279a350be6bc.tar.bz2 |
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 into for-rmk
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 0000000..3c23e05 --- /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. |