doc: update 'enable_ivshmem'
Add notification (doorbell) usage for ivshmem devices.
@@ -66,6 +66,32 @@ enable it using the :ref:`acrn_configuration_tool` with these steps:
- Build the XML configuration, refer to :ref:`getting-started-building`
+ivshmem notification mechanism
+******************************
+
+Notification (doorbell) of ivshmem device allows VMs with ivshmem
+devices enabled to notify (interrupt) each other following this flow:
+
+Notification Sender (VM):
+ VM triggers the notification to target VM by writing target Peer ID
+ (Equals to VM ID of target VM) and vector index to doorbell register of
+ ivshmem device, the layout of doorbell register is described in
+ :ref:`ivshmem-hld`.
+
+Hypervisor:
+ When doorbell register is programmed, hypervisor will search the
+ target VM by target Peer ID and inject MSI interrupt to the target VM.
+
+Notification Receiver (VM):
+ VM receives MSI interrupt and forward it to related application.
+
+ACRN supports up to 8 (MSI-X) interrupt vectors for ivshmem device.
+Guest VMs shall implement their own mechanism to forward MSI interrupts
+to applications.
+
+.. note:: Notification is supported only for HV-land ivshmem devices. (Future
+ support may include notification for DM-land ivshmem devices.)
+
Inter-VM Communication Examples
*******************************
