view Documentation/x86_64/cpu-hotplug-spec @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
line source
1 Firmware support for CPU hotplug under Linux/x86-64
2 ---------------------------------------------------
4 Linux/x86-64 supports CPU hotplug now. For various reasons Linux wants to
5 know in advance boot time the maximum number of CPUs that could be plugged
6 into the system. ACPI 3.0 currently has no official way to supply
7 this information from the firmware to the operating system.
9 In ACPI each CPU needs an LAPIC object in the MADT table ( in the
10 ACPI 3.0 specification). ACPI already has the concept of disabled LAPIC
11 objects by setting the Enabled bit in the LAPIC object to zero.
13 For CPU hotplug Linux/x86-64 expects now that any possible future hotpluggable
14 CPU is already available in the MADT. If the CPU is not available yet
15 it should have its LAPIC Enabled bit set to 0. Linux will use the number
16 of disabled LAPICs to compute the maximum number of future CPUs.
18 In the worst case the user can overwrite this choice using a command line
19 option (additional_cpus=...), but it is recommended to supply the correct
20 number (or a reasonable approximation of it, with erring towards more not less)
21 in the MADT to avoid manual configuration.