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doc: update 'enable_ivshmem'

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Add notification (doorbell) usage for ivshmem devices.

Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>
Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
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Yonghua Huang 2020-12-01 23:09:04 +08:00 committed by David Kinder
parent a95e019045
commit eb4f335dab
1 changed files with 35 additions and 9 deletions
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doc/tutorials/enable_ivshmem.rst
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@ -50,22 +50,48 @@ enable it using the :ref:`acrn_configuration_tool` with these steps:
communication VMs in ACRN scenario XML configuration. The ``IVSHMEM_REGION`` communication VMs in ACRN scenario XML configuration. The ``IVSHMEM_REGION``
format is ``shm_name,shm_size,VM IDs``: format is ``shm_name,shm_size,VM IDs``:
- ``shm_name`` - Specify a shared memory name. The name needs to start - ``shm_name`` - Specify a shared memory name. The name needs to start
with the ``hv:/`` prefix. For example, ``hv:/shm_region_0`` with the ``hv:/`` prefix. For example, ``hv:/shm_region_0``
- ``shm_size`` - Specify a shared memory size. The unit is megabyte. The - ``shm_size`` - Specify a shared memory size. The unit is megabyte. The
size ranges from 2 megabytes to 512 megabytes and must be a power of 2 megabytes. size ranges from 2 megabytes to 512 megabytes and must be a power of 2 megabytes.
For example, to set up a shared memory of 2 megabytes, use ``2`` For example, to set up a shared memory of 2 megabytes, use ``2``
instead of ``shm_size``. instead of ``shm_size``.
- ``VM IDs`` - Specify the VM IDs to use the same shared memory - ``VM IDs`` - Specify the VM IDs to use the same shared memory
communication and separate it with ``:``. For example, the communication and separate it with ``:``. For example, the
communication between VM0 and VM2, it can be written as ``0:2`` communication between VM0 and VM2, it can be written as ``0:2``
.. note:: You can define up to eight ``ivshmem`` hv-land shared regions. .. note:: You can define up to eight ``ivshmem`` hv-land shared regions.
- Build the XML configuration, refer to :ref:`getting-started-building` - 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 Inter-VM Communication Examples
******************************* *******************************