diff --git a/log/log.go b/log/log.go
index ce82b1e..85d05f6 100644
--- a/log/log.go
+++ b/log/log.go
@@ -4,13 +4,22 @@ import (
 	"bytes"
 	"fmt"
 	"os"
-	"sync"
 
 	"github.com/icexin/eggos/console"
 	"github.com/icexin/eggos/drivers/uart"
 	"github.com/icexin/eggos/kernel/sys"
 )
 
+type LogLevel int8
+
+const (
+	LoglvlDebug LogLevel = iota
+	LoglvlInfo
+	LoglvlWarn
+	LoglvlError
+	LoglvlNone
+)
+
 const (
 	loglvlEnv      = "EGGOS_LOGLVL"
 	loglvlEnvDebug = "debug"
@@ -19,39 +28,43 @@ const (
 	loglvlEnvError = "error"
 	loglvlEnvNone  = "none"
 
-	loglvlDebug = iota
-	loglvlInfo
-	loglvlWarn
-	loglvlError
-	loglvlNone
-
-	defaultLoglvl = loglvlError
+	defaultLoglvl = LoglvlError
 )
 
 var (
-	loglvl     int
-	loglvlonce sync.Once
+	Level LogLevel
+
+	ErrInvalidLogLevel = fmt.Errorf("invalid log level")
 )
 
-func setLoglvl() {
+func init() {
 	lvl := os.Getenv("EGGOS_LOGLVL")
 	switch lvl {
 	case loglvlEnvDebug:
-		loglvl = loglvlDebug
+		Level = LoglvlDebug
 	case loglvlEnvInfo:
-		loglvl = loglvlInfo
+		Level = LoglvlInfo
 	case loglvlEnvWarn:
-		loglvl = loglvlWarn
+		Level = LoglvlWarn
 	case loglvlEnvError:
-		loglvl = loglvlError
+		Level = LoglvlError
 	default:
-		loglvl = defaultLoglvl
+		Level = defaultLoglvl
 	}
 }
 
-func logf(lvl int, fmtstr string, args ...interface{}) {
-	loglvlonce.Do(setLoglvl)
-	if lvl < loglvl {
+func SetLevel(l LogLevel) error {
+	if l < LoglvlDebug || l > LoglvlNone {
+		return ErrInvalidLogLevel
+	}
+
+	Level = l
+
+	return nil
+}
+
+func logf(lvl LogLevel, fmtstr string, args ...interface{}) {
+	if lvl < Level {
 		return
 	}
 
@@ -62,19 +75,19 @@ func logf(lvl int, fmtstr string, args ...interface{}) {
 }
 
 func Debugf(fmtstr string, args ...interface{}) {
-	logf(loglvlDebug, fmtstr, args...)
+	logf(LoglvlDebug, fmtstr, args...)
 }
 
 func Infof(fmtstr string, args ...interface{}) {
-	logf(loglvlInfo, fmtstr, args...)
+	logf(LoglvlInfo, fmtstr, args...)
 }
 
 func Warnf(fmtstr string, args ...interface{}) {
-	logf(loglvlWarn, fmtstr, args...)
+	logf(LoglvlWarn, fmtstr, args...)
 }
 
 func Errorf(fmtstr string, args ...interface{}) {
-	logf(loglvlError, fmtstr, args...)
+	logf(LoglvlError, fmtstr, args...)
 }
 
 //go:nosplit
diff --git a/log/log_test.go b/log/log_test.go
new file mode 100644
index 0000000..7e0a3de
--- /dev/null
+++ b/log/log_test.go
@@ -0,0 +1,48 @@
+package log_test
+
+import (
+	"testing"
+
+	"github.com/icexin/eggos/log"
+)
+
+func ExampleSetLogLevel() {
+	// Set the log level to Debug
+	log.Level = log.LoglvlDebug
+}
+
+func TestLog_SetLevel(t *testing.T) {
+	for _, test := range []struct {
+		name        string
+		l           log.LogLevel
+		expectError bool
+	}{
+		// These two cases require users to do something pretty explcitly
+		// wrong to hit, but they're worth catching
+		{"log level is too low", log.LogLevel(-1), true},
+		{"log level is too high", log.LogLevel(6), true},
+
+		// Included log levels
+		{"log.LoglvlDebug is valid", log.LoglvlDebug, false},
+		{"log.LoglvlInfo is valid", log.LoglvlInfo, false},
+		{"log.LoglvlWarn is valid", log.LoglvlWarn, false},
+		{"log.LoglvlError is valid", log.LoglvlError, false},
+		{"log.LoglvlNone is valid", log.LoglvlNone, false},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			err := log.SetLevel(test.l)
+
+			if err == nil && test.expectError {
+				t.Error("expected error, received none")
+			} else if err != nil && !test.expectError {
+				t.Errorf("unexpected error: %#v", err)
+			}
+
+			if !test.expectError {
+				if log.Level != test.l {
+					t.Errorf("log.Level should be %#v, received %#v", log.Level, test.l)
+				}
+			}
+		})
+	}
+}