LookingGlass/module/README.md

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This kernel module implements a basic interface to the IVSHMEM device for
LookingGlass when using LookingGlass in VM->VM mode.
Additionally, in VM->host mode, it can be used to generate a shared memory
device on the host machine that supports dmabuf.
## Compiling (Manual)
Make sure you have your kernel headers installed first, on Debian/Ubuntu use
the following command.
apt-get install linux-headers-$(uname -r)
Then simply run `make` and you're done.
### Loading
For VM->VM mode, simply run:
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:
insmod kvmfr.ko static_size_mb=128
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)
You can install this module into DKMS so that it persists across kernel
upgrades. Simply run:
dkms install .
### Loading
For VM->VM, simply modprobe the module:
modprobe kvmfr
For VM->host with dmabuf, modprobe with the parameter `static_size_mb`:
modprobe kvmfr static_size_mb=128
Just like above, multiple devices can be created by separating the sizes
with commas.
## 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:
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):
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:
./looking-glass-client -f /dev/kvmfr0
### 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:
-device ivshmem-plain,id=shmem0,memdev=looking-glass
-object memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=128M,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.
#### `libvirt`
With `libvirt`, you can use the following XML block:
```xml
<qemu:commandline>
<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:commandline>
```
Remember to add `xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'` to
the `<domain>`.
On certain distros, running libvirt this way poses issues with apparmor
and cgroups.
For apparmor, in `/etc/apparmor.d/abstractions/libvirt-qemu`, append:
# 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`:
sudo systemctl restart libvirtd.service