From cc8bd94960bb23e23e7494e726a3e7bb09d0a085 Mon Sep 17 00:00:00 2001
From: Ian Campbell <ijc@docker.com>
Date: Thu, 13 Jul 2017 15:23:14 +0100
Subject: [PATCH] qemu: allow kvm and containerized options to be overridden by
 the environment

This is useful in the case where Moby is shelling out to LinuxKit for certain
image types (currently raw and qcow2). Currently to experiment with different
options (e.g. when comparing performance to CI) you have to edit either the
moby or linuxkit tool to change the options used.

The environment variables take precedence over any explict command line options
given.

Signed-off-by: Ian Campbell <ijc@docker.com>
---
 src/cmd/linuxkit/run_qemu.go | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/cmd/linuxkit/run_qemu.go b/src/cmd/linuxkit/run_qemu.go
index 354e1bdae..c1e5b9892 100644
--- a/src/cmd/linuxkit/run_qemu.go
+++ b/src/cmd/linuxkit/run_qemu.go
@@ -42,6 +42,19 @@ func haveKVM() bool {
 	return !os.IsNotExist(err)
 }
 
+func envOverrideBool(env string, b *bool) {
+	val := os.Getenv(env)
+	if val == "" {
+		return
+	}
+
+	var err error
+	*b, err = strconv.ParseBool(val)
+	if err != nil {
+		log.Fatal("Unable to parse %q=%q as a boolean", env, val)
+	}
+}
+
 func runQemu(args []string) {
 	invoked := filepath.Base(os.Args[0])
 	flags := flag.NewFlagSet("qemu", flag.ExitOnError)
@@ -89,6 +102,11 @@ func runQemu(args []string) {
 	}
 	remArgs := flags.Args()
 
+	// These envvars override the corresponding command line
+	// options. So this must remain after the `flags.Parse` above.
+	envOverrideBool("LINUXKIT_QEMU_KVM", enableKVM)
+	envOverrideBool("LINUXKIT_QEMU_CONTAINERIZED", qemuContainerized)
+
 	if len(remArgs) == 0 {
 		fmt.Println("Please specify the path to the image to boot")
 		flags.Usage()