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67 lines
2.2 KiB
ReStructuredText
67 lines
2.2 KiB
ReStructuredText
:orphan:
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.. _ivshmem_shm:
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IVSHMEM with standard shared memory
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###################################
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This method is here for those that can not use the KVMFR kernel module. Please
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be aware that as a result you will not be able to take advantage of your GPUs
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ability to access memory via it's hardware DMA engine if you use this method.
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Add the following to your libvirt machine configuration inside the
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'devices' section by running ``virsh edit <VM>`` where ``<VM>`` is the name of
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your virtual machine.
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.. code:: xml
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<shmem name='looking-glass'>
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<model type='ivshmem-plain'/>
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<size unit='M'>32</size>
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</shmem>
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.. note::
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If you are using QEMU directly without libvirt the following arguments are
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required instead.
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Add the following to the commands to your QEMU command line, adjusting
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the ``bus`` parameter to suit your particular configuration:
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.. code:: bash
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-device ivshmem-plain,memdev=ivshmem,bus=pcie.0 \
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-object memory-backend-file,id=ivshmem,share=on,mem-path=/dev/shm/looking-glass,size=32M
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The memory size (show as 32 in the example above) may need to be
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adjusted as per the :ref:`Determining memory <libvirt_determining_memory>`
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section.
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.. warning::
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If you change the size of this after starting your virtual machine you may
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need to remove the file `/dev/shm/looking-glass` to allow QEMU to re-create
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it with the correct size. If you do this the permissions of the file may be
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incorrect for your user to be able to access it and you will need to correct
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this. See :ref:`libvirt_shmfile_permissions`
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.. _libvirt_shmfile_permissions:
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Permissions
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~~~~~~~~~~~
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The shared memory file used by IVSHMEM is found in ``/dev/shm/looking-glass``.
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By default, it is owned by QEMU, and does not give read/write permissions to
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your user, which are required for Looking Glass to run properly.
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You can use ``systemd-tmpfiles`` to create the file before running your VM,
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granting the necessary permissions which allow Looking Glass to use the file
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properly.
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Create a new file ``/etc/tmpfiles.d/10-looking-glass.conf``, and populate it
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with the following::
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# Type Path Mode UID GID Age Argument
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f /dev/shm/looking-glass 0660 user kvm -
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Change ``UID`` to the user name you will run Looking Glass with, usually your
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own.
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