Ruakij/Looking-glass-kvmfr-setup-Arch.md

## Looking-glass-kvmfr-setup-Arch.md

      
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              Looking-glass-kvmfr-setup-Arch.md
            
          
    Looking-glass kvmfr setup Arch

More in-depth setup-guide for usage of kvmfr (see https://looking-glass.io/docs/B6/module/)
This setup was done on EndeavourOs (Arch) on Kernel 6.1.12-arch1-1. 

QEMU-version 7.2 and libvirt version 9.0.0 . 

Running cGroups Policy (if you have AppArmor, some things are different)
Check respective sections in looking-glass docs for other versions (specifcally QEMU <6.2 and libvirt <7.9)


1. Prerequisites

1.1. VM

You need a VM which is fully set-up with graphics-driver and the looking-glass host-program.
Documentation about that can be found here: https://looking-glass.io/docs/B6/install/


1.2. Packages

You need the following packages

sudo (or do things as root)
git
dkms
linux-headers (same version as kernel, probably already installed)


1.3. MEM-size

This guide uses the default 32MB size, which is fine for 1080p.
For 1440p or 2160p you need to use 64MB.
See this section to determine how much you need.


Formula
pixel size for SDR is 4
pixel size for HDR is 8

width x height x pixel size x 2 = frame bytes
frame bytes / 1024 / 1024 = frame megabytes
frame megabytes + 10 MiB = total megabytes

Round up to nearest power of 2. (32, 64, 128, ..)


2. Setup

2.1. kvmfr

Clone repository and enter module folder
git clone https://github.com/gnif/LookingGlass
cd LookingGlass/module
Compile and install module with dmks
sudo dkms install "."
Setup udev-rule for module to set permissions

Deviate from docs to make user-independent
sudo cat > /etc/udev/rules.d/99-kvmfr.rules <<EOF
SUBSYSTEM=="kvmfr", OWNER="libvirt-qemu", GROUP="kvm", MODE="0666"
EOF
Setup auto-load of module
sudo cat > /etc/modules-load.d/kvmfr.conf <<EOF
# 3. KVMFR Looking Glass module
kvmfr
EOF

sudo cat > /etc/modprobe.d/kvmfr.conf <<EOF
#KVMFR Looking Glass module
options kvmfr static_size_mb=32
EOF


3.1. libvirt-qemu

3.1.1. Setup cgroups-policy to allow qemu access to device


Open /etc/libvirt/qemu.conf
Find cgroup_device_acl
Uncomment everything in that block and add "/dev/kvmfr0"

Looks something like this:
# 4. This is the basic set of devices allowed / required by
# 5. all virtual machines.
#
# 6. As well as this, any configured block backed disks,
# 7. all sound device, and all PTY devices are allowed.
#                                                                                                          
# 1. This will only need setting if newer QEMU suddenly
# 2. wants some device we don't already know about.
#
cgroup_device_acl = [
    "/dev/null", "/dev/full", "/dev/zero",
    "/dev/random", "/dev/urandom",
    "/dev/ptmx", "/dev/kvm",
    "/dev/kvmfr0"
]

Save file and restart libvirtd 

sudo systemctl restart libvirtd


2.0.1. Setup VM to use MEM-device


Open virtual machine manager


Your VM -> Details -> XML


First line has to be


<domain xmlns:qemu="http://libvirt.org/schemas/domain/qemu/1.0" type="kvm">

Go to the bottom and add this block

<qemu:commandline>
  <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:commandline>
size is your MEM-size in bytes (looking-glass docs)

Formula: MEM-size x 1024 x 1024


Save and check if everything is still there

libvirt might replace " with &quot;, thats fine


2.1. Looking-Glass Client

You might not have to specify the mem-device as it already detects the correct one
Feels free to add a config-file or manually add the -f Option if not


3. Testing


Load module manually

sudo modprobe kvmfr static_size_mb=32

Check kernel-log for output of module

sudo dmesg | grep kvmfr
Should return this:

kvmfr: creating 1 static devices


Check created node and permissions

ls -la /dev/kvmfr*
Should return this:

crw-rw-rw- 1 libvirt-qemu kvm 510, 0 23. Feb 10:00 /dev/kvmfr0


Now try to start the VM and then looking-glass