f6a4217a88
Migrated existing driver samples to use the new code-sample directive and role. Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
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1.9 KiB
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58 lines
1.9 KiB
ReStructuredText
.. _ivshmem_driver:
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Inter-VM Shared Memory
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######################
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.. contents::
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:local:
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:depth: 2
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Overview
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********
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As Zephyr is enabled to run as a guest OS on Qemu and
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`ACRN <https://projectacrn.github.io/latest/tutorials/using_zephyr_as_uos.html>`_
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it might be necessary to make VMs aware of each other, or aware of the host.
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This is made possible by exposing a shared memory among parties via a feature
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called ivshmem, which stands for inter-VM Shared Memory.
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The two types are supported: a plain shared memory (ivshmem-plain) or a shared
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memory with the ability for a VM to generate an interruption on another, and
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thus to be interrupted as well itself (ivshmem-doorbell).
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Please refer to the official `Qemu ivshmem documentation
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<https://www.qemu.org/docs/master/system/devices/ivshmem.html>`_ for more information.
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Support
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*******
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Zephyr supports both versions: plain and doorbell. Ivshmem driver can be built
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by enabling :kconfig:option:`CONFIG_IVSHMEM`. By default, this will expose the plain
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version. :kconfig:option:`CONFIG_IVSHMEM_DOORBELL` needs to be enabled to get the
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doorbell version.
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Because the doorbell version uses MSI-X vectors to support notification vectors,
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the :kconfig:option:`CONFIG_IVSHMEM_MSI_X_VECTORS` has to be tweaked to the number of
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vectors that will be needed.
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Note that a tiny shell module can be exposed to test the ivshmem feature by
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enabling :kconfig:option:`CONFIG_IVSHMEM_SHELL`.
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ivshmem-v2
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**********
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Zephyr also supports ivshmem-v2:
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https://github.com/siemens/jailhouse/blob/master/Documentation/ivshmem-v2-specification.md
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This is primarily used for IPC in the Jailhouse hypervisor
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(e.g. :zephyr:code-sample:`eth-ivshmem`). It is also possible to use ivshmem-v2 without
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Jailhouse by building the Siemens fork of QEMU, and modifying the QEMU launch flags:
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https://github.com/siemens/qemu/tree/wip/ivshmem2
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API Reference
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*************
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.. doxygengroup:: ivshmem
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