Owing to his constant knowledge of everything is he called Sarva. Krishna is established on truth and truth is established on him.
सर्वस्य च सदा ज्ञानात् सर्वमेतं प्रचक्षते। सत्ये प्रतिष्ठितः कृष्णः सत्यपत्र प्रतिष्ठितम्॥