diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 583f71abbe98..7c6a0a41676f 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -76,7 +76,8 @@ alternative_else_nop_endif
 #ifdef CONFIG_VMAP_STACK
 	/*
 	 * Test whether the SP has overflowed, without corrupting a GPR.
-	 * Task and IRQ stacks are aligned to (1 << THREAD_SHIFT).
+	 * Task and IRQ stacks are aligned so that SP & (1 << THREAD_SHIFT)
+	 * should always be zero.
 	 */
 	add	sp, sp, x0			// sp' = sp + x0
 	sub	x0, sp, x0			// x0' = sp' - x0 = (sp + x0) - x0 = sp