summaryrefslogtreecommitdiffstats
path: root/docs/specs/acpi_cpu_hotplug.txt
blob: 5dec0c50102537a897898545cf8f03ec697034c4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
QEMU<->ACPI BIOS CPU hotplug interface
--------------------------------------

QEMU supports CPU hotplug via ACPI. This document
describes the interface between QEMU and the ACPI BIOS.

ACPI GPE block (IO ports 0xafe0-0xafe3, byte access):
-----------------------------------------

Generic ACPI GPE block. Bit 2 (GPE.2) used to notify CPU
hot-add/remove event to ACPI BIOS, via SCI interrupt.

CPU present bitmap (IO port 0xaf00-0xae1f, 1-byte access):
---------------------------------------------------------------
One bit per CPU. Bit position reflects corresponding CPU APIC ID.
Read-only.

CPU hot-add/remove notification:
-----------------------------------------------------
QEMU sets/clears corresponding CPU bit on hot-add/remove event.
CPU present map read by ACPI BIOS GPE.2 handler to notify OS of CPU
hot-(un)plug events.
OpenPOWER on IntegriCloud