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[docs] guide: document current Looking Glass features

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Geoffrey McRae
2026-08-11 19:18:17 +10:00
parent 45429681a0
commit 33bdc611d8
36 changed files with 2356 additions and 1328 deletions
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27
doc/ivshmem_kvmfr.rst
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@@ -4,8 +4,8 @@
IVSHMEM with the KVMFR module (Recommended)
###########################################
The kernel module implements a basic interface to the IVSHMEM device
for Looking Glass allowing DMA GPU transfers.
The kernel module exposes IVSHMEM to Looking Glass and can export its frame
buffers for direct GPU import.
.. _ivshmem_kvmfr_prereq:
@@ -47,14 +47,14 @@ Using the value you should have already calculated as per
.. code:: bash
modprobe kvmfr static_size_mb=32
modprobe kvmfr static_size_mb=64
Alternatively you can make this setting permanent by creating the file
``/etc/modprobe.d/kvmfr.conf`` with the following content.
.. code:: text
options kvmfr static_size_mb=32
options kvmfr static_size_mb=64
After this has been done, simply running ``modprobe kvmfr`` is all that is
required.
@@ -102,9 +102,11 @@ You should now also have the character device ``/dev/kvmfr0``
If you start the VM prior to loading the module, QEMU will create the file
``/dev/kvmfr0`` as a regular file. You can confirm if this has happened by
running ``ls -l /dev/kvmfr0`` and checking if the file size is greater then
running ``ls -l /dev/kvmfr0`` and checking if the file size is greater than
zero, or the permissions do not start with ``c``. If this has occurred, you
must delete the file and reload the module.
must stop the VM before deleting the regular file. Load the KVMFR module,
confirm that it recreated ``/dev/kvmfr0`` as a character device whose
permissions start with ``c``, then start the VM again.
.. _ivhsmem_kvmfr_permissions:
@@ -165,7 +167,7 @@ should use this XML block to configure their VM for kvmfr:
<qemu:arg value="-device"/>
<qemu:arg value="{'driver':'ivshmem-plain','id':'shmem0','memdev':'looking-glass'}"/>
<qemu:arg value="-object"/>
<qemu:arg value="{'qom-type':'memory-backend-file','id':'looking-glass','mem-path':'/dev/kvmfr0','size':33554432,'share':true}"/>
<qemu:arg value="{'qom-type':'memory-backend-file','id':'looking-glass','mem-path':'/dev/kvmfr0','size':67108864,'share':true}"/>
</qemu:commandline>
.. note::
@@ -186,7 +188,7 @@ legacy syntax for IVSHMEM setup:
<qemu:arg value="-device"/>
<qemu:arg value="ivshmem-plain,id=shmem0,memdev=looking-glass"/>
<qemu:arg value="-object"/>
<qemu:arg value="memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=32M,share=yes"/>
<qemu:arg value="memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=64M,share=yes"/>
</qemu:commandline>
.. note::
@@ -218,9 +220,9 @@ and add the following:
cgroups
^^^^^^^
Edit the file ``/etc/libvirt/qemu.conf`` and uncomment the ``cgroup_device_acl``
block, adding ``/dev/kvmfr0`` to the list. To make this change active you then
must restart ``libvirtd``
Edit the file ``/etc/libvirt/qemu.conf`` and uncomment the
``cgroup_device_acl`` block, adding ``/dev/kvmfr0`` to the list. Restart
``libvirtd`` to apply it:
.. code:: bash
@@ -235,10 +237,9 @@ If you are using QEMU directly without libvirt, add the following arguments to y
``qemu`` command line::
-device ivshmem-plain,id=shmem0,memdev=looking-glass
-object memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=32M,share=yes
-object memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=64M,share=yes
.. note::
The ``size`` argument must be the same size you passed
to the ``static_size_mb`` argument when loading the kernel module.