@@ -4,21 +4,85 @@ 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.
+ACPI BIOS GPE.2 handler is dedicated for notifying OS about CPU hot-add
+and hot-remove events.
+============================================
+Legacy ACPI CPU hotplug interface registers:
+--------------------------------------------
CPU present bitmap for:
+ One bit per CPU. Bit position reflects corresponding CPU APIC ID. Read-only.
ICH9-LPC (IO port 0x0cd8-0xcf7, 1-byte access)
PIIX-PM (IO port 0xaf00-0xaf1f, 1-byte access)
---------------------------------------------------------------
-One bit per CPU. Bit position reflects corresponding CPU APIC ID.
-Read-only.
+QEMU sets corresponding CPU bit on hot-add event and issues SCI
+with GPE.2 event set. CPU present map read by ACPI BIOS GPE.2 handler
+to notify OS about CPU hot-add events. CPU hot-remove isn't supported.
+
+=====================================
+ACPI CPU hotplug interface registers:
+-------------------------------------
+Register block base address:
+ ICH9-LPC IO port 0x0cd8
+ PIIX-PM IO port 0xaf00
+Register block size:
+ ACPI_CPU_HOTPLUG_REG_LEN = 12
+
+read access:
+ offset:
+ [0x0-0x3] reserved
+ [0x4] CPU device status fields: (1 byte access)
+ bits:
+ 0: Device is enabled and may be used by guest
+ 1: Device insert event, used to distinguish device for which
+ no device check event to OSPM was issued.
+ It's valid only when bit 0 is set.
+ 2: Device remove event, used to distinguish device for which
+ no device eject request to OSPM was issued.
+ 3-7: reserved and should be ignored by OSPM
+ [0x5-0x7] reserved
+ [0x8] Command data: (DWORD access)
+ in case of error or unsupported command reads is 0xFFFFFFFF
+ current 'Command field' value:
+ 0: returns PXM value corresponding to device
+
+write access:
+ offset:
+ [0x0-0x3] CPU selector: (DWORD access)
+ selects active CPU device. All following accesses to other
+ registers will read/store data from/to selected CPU.
+ [0x4] CPU device control fields: (1 byte access)
+ bits:
+ 0: reserved, OSPM must clear it before writing to register.
+ 1: if set to 1 clears device insert event, set by OSPM
+ after it has emitted device check event for the
+ selected CPU device
+ 2: if set to 1 clears device remove event, set by OSPM
+ after it has emitted device eject request for the
+ selected CPU device
+ 3: if set to 1 initiates device eject, set by OSPM when it
+ triggers CPU device removal and calls _EJ0 method
+ 4-7: reserved, OSPM must clear them before writing to register
+ [0x5] Command field: (1 byte access)
+ value:
+ 0: following reads from 'Command data' register returns PXM
+ value of device
+ 1: following writes to 'Command data' register set OST event
+ register in QEMU
+ 2: following writes to 'Command data' register set OST status
+ register in QEMU
+ other values: reserved
+ [0x6-0x7] reserved
+ [0x8] Command data: (DWORD access)
+ current 'Command field' value:
+ 1: stores value into OST event register
+ 2: stores value into OST status register, triggers
+ ACPI_DEVICE_OST QMP event from QEMU to external applications
+ with current values of OST event and status registers.
+ other values: reserved
-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.
+Selecting CPU device beyond possible range has no effect on platform:
+ - write accesses to CPU hot-plug registers not documented above are
+ ignored
+ - read accesses to CPU hot-plug registers not documented above return
+ all bits set to 1.
Signed-off-by: Igor Mammedov <imammedo@redhat.com> --- docs/specs/acpi_cpu_hotplug.txt | 88 +++++++++++++++++++++++++++++++++++------ 1 file changed, 76 insertions(+), 12 deletions(-)