docs/specs/acpi_cpu_hotplug.rst

1 QEMU<->ACPI BIOS CPU hotplug interface
7 ACPI BIOS GPE.2 handler is dedicated for notifying OS about CPU hot-add
8 and hot-remove events.
12 -------------------------------------------
16 - ICH9-LPC (IO port 0x0cd8-0xcf7, 1-byte access)
17 - PIIX-PM  (IO port 0xaf00-0xaf1f, 1-byte access)
18 - One bit per CPU. Bit position reflects corresponding CPU APIC ID. Read-only.
19 - The first DWORD in bitmap is used in write mode to switch from legacy
22 QEMU sets corresponding CPU bit on hot-add event and issues SCI
23 with GPE.2 event set. CPU present map is read by ACPI BIOS GPE.2 handler
24 to notify OS about CPU hot-add events. CPU hot-remove isn't supported.
28 -------------------------------------------
32 - ICH9-LPC IO port 0x0cd8
33 - PIIX-PM  IO port 0xaf00
37 - ACPI_CPU_HOTPLUG_REG_LEN = 12
39 All accesses to registers described below, imply little-endian byte order.
43 - write accesses are ignored
44 - read accesses return all bits set to 0.
48 - reads from any register return 0
49 - writes to any other register are ignored until valid value is stored into it
57 offset [0x0-0x3]
65     upper 32 bits of architecture specific CPU ID value
77     Device insert event, used to distinguish device for which
78     no device check event to OSPM was issued.
81     Device remove event, used to distinguish device for which
88   5-7:
91 offset [0x5-0x7]
100     contains 'CPU selector' value of a CPU with pending event[s]
102     lower 32 bits of architecture specific CPU ID value
110 offset [0x0-0x3]
125     if set to 1 clears device insert event, set by OSPM
126     after it has emitted device check event for the
129     if set to 1 clears device remove event, set by OSPM
142   5-7:
155     change and corresponding insert/remove event flags are not modified.
158     following writes to 'Command data' register set OST event
165     architecture specific CPU ID value for currently selected CPU.
169 offset [0x6-0x7]
178     stores value into OST event register
181     ACPI_DEVICE_OST QMP event from QEMU to external applications
182     with current values of OST event and status registers.
187 ----------------
207 Get a cpu with pending event
214    with a pending event and selected CPU remains unchanged.
216    selector of the CPU with the pending event (which is already selected).