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>
diff --git a/docs/specs/acpi_pci_hotplug.txt b/docs/specs/acpi_pci_hotplug.txt
index f0f74a7..1e2c8a2 100644
--- a/docs/specs/acpi_pci_hotplug.txt
+++ b/docs/specs/acpi_pci_hotplug.txt
@@ -15,14 +15,14 @@
Slot injection notification pending. One bit per slot.
Read by ACPI BIOS GPE.1 handler to notify OS of injection
-events.
+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.
+events. Read-only.
PCI device eject (IO port 0xae08-0xae0b, 4-byte access):
----------------------------------------
