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Virtualization.adoc

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General rules of thumb

  1. Anytime files under /etc/modprobe.d are created or modified, run mkinitcpio -P after done.

  2. If you want to share a mouse, keyboard, clipboard, and use the same display, use https://looking-glass.io/docs/B6/install

Mouse and Keyboard ultra low-latency, with a virtual KVM switch (evdev method)

  1. Get what will be your input device, for example: # cat /dev/input/by-id/usb-IDOBAO_ID87-event-kbd

    • event-kbd for Keyboards, event-mouse for Mice.

    • You want to see output when you interact with that keyboard or mice, that’s how you tell it is the correct choice.

  2. Put it into your libvirt XML, such as:

<qemu:commandline>
    <qemu:arg value='-object'/>
    <qemu:arg value='input-linux,id=mouse1,evdev=/dev/input/by-id/usb-Xtrfy_Xtrfy_Wireless_Receiver-event-mouse'/>
    <qemu:arg value='-object'/>
    <qemu:arg value='input-linux,id=kbd1,evdev=/dev/input/by-id/usb-IDOBAO_ID87-event-kbd,grab_all=on,repeat=on'/>
</qemu:commandline>

  1. Run gpasswd -a libvirt-qemu input to give the required 'input' permissions.

What I do in my VM config

  1. Increasing performance, meant only for single VM use cases:

    • Memory locking, and CPU Power Management increase performance; these are set via qemu:commandline.

    • Turning off CPU migratable: <cpu mode="host-passthrough" check="none" migratable="off">

    • Turning off Memory Ballooning: <memballoon model="none"/> → inside <devices> block.

    • Enabling hyper-threading: <feature policy="require" name="topoext"/> → <cpu> block

    • <nosharepages/> and <locked/> → <memoryBacking> block.

  2. Workarounds:

    • <maxphysaddr mode="passthrough" limit="39"/>: the VM will crash without this on an Intel 12700k CPU, given a Looking Glass 'shmem' device is used.

CPU core/thread automatic isolation, for performance stability

  1. Open lstopo to verify that the cores on the host are now locked to what you set.