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111 lines
3.2 KiB
Markdown
111 lines
3.2 KiB
Markdown
This kernel module implements a basic interface to the IVSHMEM device for
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LookingGlass when using LookingGlass in VM->VM mode.
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Additionally, in VM->host mode, it can be used to generate a shared memory
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device on the host machine that supports dmabuf.
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## Compiling (Manual)
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Make sure you have your kernel headers installed first, on Debian/Ubuntu use
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the following command.
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apt-get install linux-headers-$(uname -r)
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Then simply run `make` and you're done.
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### Loading
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For VM->VM mode, simply run:
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insmod kvmfr.ko
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For VM->host mode with dmabuf, instead of creating a shared memory file, load
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this module with the parameter `static_size_mb`. For example, a 128 MB shared
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memory device can be created with:
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insmod kvmfr.ko static_size_mb=128
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Multiple devices can be created by separating the sizes with commas. For
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example, `static_size_mb=128,64` would create two kvmfr devices: `kvmfr0`
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would be 128 MB and `kvmfr1` would be 64 MB.
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## Compiling & Installing (DKMS)
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You can install this module into DKMS so that it persists across kernel
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upgrades. Simply run:
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dkms install .
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### Loading
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For VM->VM, simply modprobe the module:
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modprobe kvmfr
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For VM->host with dmabuf, modprobe with the parameter `static_size_mb`:
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modprobe kvmfr static_size_mb=128
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Just like above, multiple devices can be created by separating the sizes
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with commas.
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## Usage
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This will create the `/dev/kvmfr0` node that represents the KVMFR interface.
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To use the interface you need permission to access it by either creating a
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udev rule to ensure your user can read and write to it, or simply change its
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ownership manually, ie:
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sudo chown user:user /dev/kvmfr0
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An example udev rule, which you can put in `/etc/udev/rules.d/99-kvmfr.rules`,
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is (replace `user` with your username):
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SUBSYSTEM=="kvmfr", OWNER="user", GROUP="kvm", MODE="0660"
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Usage with looking glass is simple, you only need to specify the path to the
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device node, for example:
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./looking-glass-client -f /dev/kvmfr0
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### VM->Host
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In VM->host mode, use this device in place of the shared memory file.
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For example, with `qemu`, you would use the following arguments:
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-device ivshmem-plain,id=shmem0,memdev=looking-glass
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-object memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=128M,share=yes
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Note that the `size` argument must be the same size as what you passed
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to `static_size_mb` argument for the kernel module.
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#### `libvirt`
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With `libvirt`, you can use the following XML block:
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```xml
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<qemu:commandline>
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<qemu:arg value='-device'/>
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<qemu:arg value='ivshmem-plain,id=shmem0,memdev=looking-glass'/>
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<qemu:arg value='-object'/>
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<qemu:arg value='memory-backend-file,id=looking-glass,mem-path=/dev/kvmfr0,size=128M,share=yes'/>
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</qemu:commandline>
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```
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Remember to add `xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'` to
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the `<domain>`.
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On certain distros, running libvirt this way poses issues with apparmor
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and cgroups.
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For apparmor, in `/etc/apparmor.d/abstractions/libvirt-qemu`, append:
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# Looking Glass
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/dev/kvmfr0 rw,
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For cgroups, in `/etc/libvirt/qemu.conf`, uncomment the `cgroup_device_acl`
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block and add `/dev/kvmfr0` to the list. Then restart `libvirtd`:
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sudo systemctl restart libvirtd.service
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