Brett T. Warden bwarden

Tracing QEMU-KVM Interactions

But default in linux you can figure out how many times and for what reasons there is a VM Exit from a VM into the kvm kernel module. However given the ubiquity of vhost and the ability of kvm to emulate most device models directly in the kernel, most of those VM exits do not result in a transition from host kernel into the QEMU. The transitions from VM -> kvm -> QEMU are typically the most expensive.

Here we try to figure out how many of the VM Exits result in the invocation of QEMU.

Tracking VM-KVM Interactions

This can be done very simply with perf

	#!/bin/bash

	# Remove existing "nameserver" lines from /etc/resolv.conf
	sed -i '/nameserver/d' /etc/resolv.conf

	# Run the PowerShell command to generate "nameserver" lines and append to /etc/resolv.conf
	# we use full path here to support boot command with root user
	/mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe -Command '(Get-DnsClientServerAddress -AddressFamily IPv4).ServerAddresses \| ForEach-Object { "nameserver $_" }' \| tr -d '\r'\| tee -a /etc/resolv.conf > /dev/null

	#!/usr/bin/env bash

	set -o errexit
	set -o pipefail
	set -o nounset
	# set -o xtrace

	PWD="$(pwd)"

	die () {

	VOLUME UP:
	One line: FFA25D:NEC:32
	uint16_t rawData[67] = {8980,4486, 544,572, 542,574, 542,572, 542,574, 542,572, 544,572, 542,572, 544,578, 542,1654, 542,1654, 542,1652, 544,1654, 542,1652, 542,1652, 544,1652, 542,1636, 564,1652, 544,572, 544,1652, 542,550, 566,572, 544,572, 542,1652, 542,578, 542,572, 544,1652, 542,572, 542,1654, 542,1652, 544,1652, 544,572, 542,1654, 542}; // NEC FFA25D
	uint32_t address = 0x0;
	uint32_t command = 0x45;
	uint64_t data = 0xFFA25D;

	VOLUME DOWN:
	One line: FF827D:NEC:32
	uint16_t rawData[67] = {8980,4486, 542,572, 544,572, 544,546, 568,572, 544,572, 542,572, 542,572, 544,556, 564,1652, 544,1654, 542,1654, 542,1652, 544,1652, 542,1652, 544,1652, 544,1658, 542,1652, 544,572, 542,572, 544,572, 616,498, 544,572, 544,1654, 542,578, 542,574, 542,1652, 544,1654, 542,1654, 542,1652, 542,1652, 544,572, 544,1634, 564}; // NEC FF827D

	To make Pageant automatically run and load keys at startup:

	- Find the location of pageant.exe

	- Windows key + R to open the 'run' dialog box

	- Type: 'shell:startup' in the dialog box

	- Create a shortcut to the pageant.exe and put into this startup folder.