qemu-e2k/docs/specs/acpi_pci_hotplug.txt
Alex Williamson ba737541ed acpi_piix4: Disallow write to up/down PCI hotplug registers
The write side of these registers is never used and actually can't be
used as defined because any read/modify/write sequence from the guest
potentially races with qemu.  Drop the write support and define these
as read-only registers.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2012-04-15 12:17:22 +03:00

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QEMU<->ACPI BIOS PCI hotplug interface
--------------------------------------
QEMU supports PCI hotplug via ACPI, for PCI bus 0. 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 1 (GPE.1) used to notify PCI hotplug/eject
event to ACPI BIOS, via SCI interrupt.
PCI slot injection notification pending (IO port 0xae00-0xae03, 4-byte access):
---------------------------------------------------------------
Slot injection notification pending. One bit per slot.
Read by ACPI BIOS GPE.1 handler to notify OS of injection
events. Read-only.
PCI slot removal notification (IO port 0xae04-0xae07, 4-byte access):
-----------------------------------------------------
Slot removal notification pending. One bit per slot.
Read by ACPI BIOS GPE.1 handler to notify OS of removal
events. Read-only.
PCI device eject (IO port 0xae08-0xae0b, 4-byte access):
----------------------------------------
Used by ACPI BIOS _EJ0 method to request device removal. One bit per slot.
Reads return 0.
PCI removability status (IO port 0xae0c-0xae0f, 4-byte access):
-----------------------------------------------
Used by ACPI BIOS _RMV method to indicate removability status to OS. One
bit per slot.