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doc: update the 'ivshmem' HLD

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Update the 'ivshmem' document to clarify the existence of two similar
mechanisms to expose this device to User VMs. One is implemented in the ACRN
Device Model and another (future) is implemented in the hypervisor.

Signed-off-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>
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Geoffroy Van Cutsem 2020-06-10 15:46:16 +02:00 committed by deb-intel
parent 7c7bf767f6
commit 5d08f2518f
3 changed files with 16 additions and 9 deletions
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doc/developer-guides/hld/ivshmem-hld.rst
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@ -4,14 +4,14 @@ ACRN Shared Memory Based Inter-VM Communication
############################################### ###############################################
ACRN supports inter-virtual machine communication based on a shared ACRN supports inter-virtual machine communication based on a shared
memory mechanism, The ACRN device model and hypervisor emulate a virtual memory mechanism. The ACRN device model or hypervisor emulate a virtual
PCI device (called an ``ivshmem`` device) to expose the base address and PCI device (called an ``ivshmem`` device) to expose the base address and
size of this shared memory. size of this shared memory.
Inter-VM Communication Overview Inter-VM Communication Overview
******************************* *******************************
.. figure:: images/ivshmem-image1.png .. figure:: images/ivshmem-architecture.png
:align: center :align: center
:name: ivshmem-architecture-overview :name: ivshmem-architecture-overview
@ -27,15 +27,19 @@ VMs.
memory regions reserved in the hypervisor's memory space. This solution memory regions reserved in the hypervisor's memory space. This solution
would work for both pre-launched and post-launched VMs. would work for both pre-launched and post-launched VMs.
ivshmem hv: ivshmem hv:
The ivshmem device model implements register virtualization The **ivshmem hv** implements register virtualization
and shared memory mapping in the hypervisor (not the acrn-dm). and shared memory mapping in the ACRN hypervisor.
Will support notification/interrupt mechanism in the future. It will support notification/interrupt mechanism in the future.
ivshmem dm:
The **ivshmem dm** implements register virtualization
and shared memory mapping in the ACRN Device Model (``acrn-dm``).
It will support notification/interrupt mechanism in the future.
ivshmem server: ivshmem server:
A daemon for inter-VM notification capability, A daemon for inter-VM notification capability, that will work with **ivshmem
This is currently **not implemented**, so the inter-VM communication dm**. This is currently **not implemented**, so the inter-VM communication
doesn't support a notification mechanism. doesn't support a notification mechanism.
Ivshmem Device Introduction Ivshmem Device Introduction
@ -96,7 +100,7 @@ Usage
***** *****
To support two post-launched VMs communicating via an ``ivshmem`` device, To support two post-launched VMs communicating via an ``ivshmem`` device,
add this line as an acrn-dm boot parameter:: add this line as an ``acrn-dm`` boot parameter::
-s slot,ivshmem,shm_name,shm_size -s slot,ivshmem,shm_name,shm_size
@ -112,6 +116,7 @@ where
- ``shm_size`` - Specify a shared memory size. The two communicating - ``shm_size`` - Specify a shared memory size. The two communicating
VMs must define the same size. VMs must define the same size.
.. note:: This device can be used with Real-Time VM (RTVM) as well.
Inter-VM Communication Example Inter-VM Communication Example
****************************** ******************************
@ -119,6 +124,8 @@ Inter-VM Communication Example
The following example uses inter-vm communication between two Linux-based post-launched VMs (VM1 and The following example uses inter-vm communication between two Linux-based post-launched VMs (VM1 and
VM2). VM2).
.. note:: An ``ivshmem`` Windows driver exists and can be found `here <https://github.com/virtio-win/kvm-guest-drivers-windows/tree/master/ivshmem>`_
1. Add a new virtual PCI device for both VMs: the device type is 1. Add a new virtual PCI device for both VMs: the device type is
``ivshmem``, shared memory name is ``test`` and shared memory size is ``ivshmem``, shared memory name is ``test`` and shared memory size is
4096 bytes. Both VMs must have the same shared memory name and size: 4096 bytes. Both VMs must have the same shared memory name and size: