[doc] module: Touchups

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Jonathan Rubenstein 2021-07-05 13:24:30 -04:00 committed by Geoffrey McRae
parent 6f5e5aa0c2
commit acac8b40cb

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@ -1,50 +1,84 @@
.. _kernel_module:
Kernel Module
#############
This kernel module implements a basic interface to the IVSHMEM device
for LookingGlass when using LookingGlass in VM->VM mode.
for Looking Glass in VM->VM mode.
Additionally, in VM->host mode, it can be used to generate a shared
Additionally in VM->host mode, it can be used to generate a shared
memory device on the host machine that supports dmabuf.
Compiling (Manual)
------------------
Prerequisites
-------------
Make sure you have your kernel headers installed first, on Debian/Ubuntu
use the following command::
The linux kernel headers for your kernel version are required for building.
Install them with ``apt-get``
.. code:: bash
apt-get install linux-headers-$(uname -r)
Then simply run ``make`` and you're done.
Then switch to the ``module/`` directory
.. code:: bash
cd module/
.. _module_manual:
Compiling & Loading (Manual)
----------------------------
To compile the module manually, run ``make`` in the module directory.
.. _module_manual_loading:
Loading
~~~~~~~
For VM->VM mode, simply run::
For VM->VM mode, run:
.. code:: bash
insmod kvmfr.ko
For VM->host mode with dmabuf, instead of creating a shared memory file,
load this module with the parameter ``static_size_mb``. For example, a
128 MB shared memory device can be created with::
32 MB shared memory device can be created with:
insmod kvmfr.ko static_size_mb=128
.. code:: bash
insmod kvmfr.ko static_size_mb=32
Multiple devices can be created by separating the sizes with commas. For
example, ``static_size_mb=128,64`` would create two kvmfr devices:
``kvmfr0`` would be 128 MB and ``kvmfr1`` would be 64 MB.
.. _compiling--installing-dkms:
.. _module_dkms:
Compiling & Installing (DKMS)
-----------------------------
Using DKMS
----------
You can install this module into DKMS so that it persists across kernel
upgrades. Simply run::
You can use the kernel's DKMS feature to keep the module across upgrades.
``dkms`` must be installed.
.. code:: bash
apt-get install dkms
.. _module_dkms_install:
Installing
~~~~~~~~~~
To install the module into DKMS, run
.. code:: bash
dkms install .
.. _loading-1:
.. _module_dkms_loading:
Loading
~~~~~~~
@ -54,31 +88,40 @@ For VM->VM, simply modprobe the module::
modprobe kvmfr
For VM->host with dmabuf, modprobe with the parameter
``static_size_mb``::
``static_size_mb``:
modprobe kvmfr static_size_mb=128
.. code:: bash
modprobe kvmfr static_size_mb=32
Just like above, multiple devices can be created by separating the sizes
with commas.
.. _module_usage:
Usage
-----
This will create the ``/dev/kvmfr0`` node that represents the KVMFR
interface. To use the interface you need permission to access it by
either creating a udev rule to ensure your user can read and write to
it, or simply change its ownership manually, ie::
The module will create the ``/dev/kvmfr0`` node, which represents the KVMFR
interface. To use the interface, you need permission to access it by
either: creating a udev rule to ensure your user can read and write to
it, or simply change its ownership manually, ie:
.. code:: bash
sudo chown user:user /dev/kvmfr0
An example udev rule, which you can put in
``/etc/udev/rules.d/99-kvmfr.rules``, is (replace ``user`` with your
username)::
As an example, you can create a new file in ``/etc/udev/rules.d/99-kvmfr.rules``
with the following contents::
SUBSYSTEM=="kvmfr", OWNER="user", GROUP="kvm", MODE="0660"
Usage with looking glass is simple, you only need to specify the path to
the device node, for example::
(replace ``user`` with your username)
Usage with Looking Glass is simple, you only need to specify the path to
the device node, for example:
.. code:: bash
./looking-glass-client -f /dev/kvmfr0
@ -90,23 +133,30 @@ You may also use a config file: ``~/.looking-glass-client.ini``, or
[app]
shmFile=/dev/kvmfr0
.. _module_vm_to_host:
VM->Host
~~~~~~~~
In VM->host mode, use this device in place of the shared memory file.
For example, with ``qemu``, you would use the following arguments::
QEMU
^^^^
Add the following arguments to your ``qemu`` command line::
-device ivshmem-plain,id=shmem0,memdev=looking-glass
-object memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=128M,share=yes
-object memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=32M,share=yes
Note that the ``size`` argument must be the same size as what you passed
to ``static_size_mb`` argument for the kernel module.
.. note::
``libvirt``
^^^^^^^^^^^
The ``size`` argument must be the same size you passed
to the ``static_size_mb`` argument when loading the kernel module.
With ``libvirt``, you can use the following XML block:
libvirt
^^^^^^^
Create the following XML block in your domain:
.. code:: xml
@ -114,25 +164,29 @@ With ``libvirt``, you can use the following XML block:
<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=128M,share=yes'/>
<qemu:arg value='memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=32M,share=yes'/>
</qemu:commandline>
Remember to add
``xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'`` to the
``<domain>``.
.. note::
On certain distros, running libvirt this way poses issues with apparmor
and cgroups.
Remember to add ``xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'``
to the ``<domain>`` tag.
For apparmor, create ``/etc/apparmor.d/local/abstractions/libvirt-qemu`` if
Running libvirt this way violates AppArmor and cgroups policies, which will
block the VM from running. These policies must be amended to allow the VM
to start.
For AppArmor, create ``/etc/apparmor.d/local/abstractions/libvirt-qemu`` if
it doesn't exist, and add the following::
# Looking Glass
/dev/kvmfr0 rw,
For cgroups, in ``/etc/libvirt/qemu.conf``, uncomment the
``cgroup_device_acl`` block and add ``/dev/kvmfr0`` to the list. Then
restart ``libvirtd``::
For cgroups, edit ``/etc/libvirt/qemu.conf``, uncomment the
``cgroup_device_acl`` block, and add ``/dev/kvmfr0`` to the list.
Then restart ``libvirtd``:
.. code:: bash
sudo systemctl restart libvirtd.service
@ -144,7 +198,7 @@ systemd-modules-load
For convenience, you may load the KVMFR module when starting your computer.
We can use the ``systemd-modules-load.service(8)`` service for this task.
Create a file as ``/etc/modules-load.d/kvmfr.conf`` with the following
Create the file ``/etc/modules-load.d/kvmfr.conf`` with the following
contents::
#KVMFR Looking Glass module
@ -152,9 +206,13 @@ contents::
This will now run the next time you start your machine.
If you are running in VM->host mode, you must additionally add another file in
If you are running in VM->host mode, you must additionally create another file
``/etc/modprobe.d/kvmfr.conf`` to properly set the size. It should have the
following contents, while adjusting ``static_size_mb`` to your needs::
following contents::
#KVMFR Looking Glass module
options kvmfr static_size_mb=128
options kvmfr static_size_mb=32
.. note::
Don't forget to adjust ``static_size_mb`` to your needs.