diff --git a/sys/arm64/arm64/genassym.c b/sys/arm64/arm64/genassym.c
--- a/sys/arm64/arm64/genassym.c
+++ b/sys/arm64/arm64/genassym.c
@@ -29,6 +29,7 @@
 #include <sys/param.h>
 #include <sys/assym.h>
 #include <sys/bus.h>
+#include <sys/msan.h>
 #include <sys/pcpu.h>
 #include <sys/proc.h>
 
@@ -38,6 +39,8 @@
 #include <machine/machdep.h>
 #include <machine/pcb.h>
 
+#include <dev/psci/smccc.h>
+
 /* Sizeof arm64_bootparams, rounded to keep stack alignment */
 ASSYM(BOOTPARAMS_SIZE, roundup2(sizeof(struct arm64_bootparams),
     STACKALIGNBYTES + 1));
@@ -88,3 +91,8 @@
 
 ASSYM(INTR_ROOT_IRQ, INTR_ROOT_IRQ);
 ASSYM(INTR_ROOT_FIQ, INTR_ROOT_FIQ);
+
+ASSYM(ARM_SMCCC_RES_SIZE, sizeof(struct arm_smccc_res));
+ASSYM(ARM_SMCCC_1_2_REGS_SIZE, sizeof(struct arm_smccc_1_2_regs));
+
+ASSYM(KMSAN_STATE_INITED, KMSAN_STATE_INITED);
diff --git a/sys/dev/psci/smccc_arm64.S b/sys/dev/psci/smccc_arm64.S
--- a/sys/dev/psci/smccc_arm64.S
+++ b/sys/dev/psci/smccc_arm64.S
@@ -34,6 +34,8 @@
 
 #include <machine/asm.h>
 
+#include "assym.inc"
+
 .macro arm_smccc_1_0	insn
 ENTRY(arm_smccc_\insn)
 	\insn	#0
@@ -41,6 +43,17 @@
 	cbz	x4, 1f
 	stp	x0, x1, [x4, #16 * 0]
 	stp	x2, x3, [x4, #16 * 1]
+#ifdef KMSAN
+	stp	x29, x30, [sp, #-32]!
+	str	x0, [sp, #16]
+	mov	x29, sp
+	mov	x0, x4
+	mov	x1, #(ARM_SMCCC_RES_SIZE)
+	mov	x2, #(KMSAN_STATE_INITED)
+	bl	kmsan_mark
+	ldr	x0, [sp, #16]
+	ldp	x29, x30, [sp], #32
+#endif
 1:	ret
 END(arm_smccc_\insn)
 .endm
@@ -55,8 +68,15 @@
 
 .macro arm_smccc_1_2	insn
 ENTRY(arm_smccc_1_2_\insn)
-	stp	x1, x19, [sp, #-16]!
+	stp	x29, x30, [sp, #-32]!
+	stp	x1, x19, [sp, #16]
+	mov	x29, sp
 	mov	x19, x0
+#ifdef KMSAN
+	mov	x1, #(ARM_SMCCC_1_2_REGS_SIZE)
+	adr	x2, .Lfunc_name_\insn
+	bl	kmsan_check
+#endif
 	ldp	x0, x1, [x19, #16 * 0]
 	ldp	x2, x3, [x19, #16 * 1]
 	ldp	x4, x5, [x19, #16 * 2]
@@ -67,7 +87,7 @@
 	ldp	x14, x15, [x19, #16 * 7]
 	ldp	x16, x17, [x19, #16 * 8]
 	\insn	#0
-	ldr	x19, [sp]
+	ldr	x19, [sp, #16]
 	cbz	x19, 1f
 	stp	x0, x1, [x19, #16 * 0]
 	stp	x2, x3, [x19, #16 * 1]
@@ -78,8 +98,22 @@
 	stp	x12, x13, [x19, #16 * 6]
 	stp	x14, x15, [x19, #16 * 7]
 	stp	x16, x17, [x19, #16 * 8]
-1:	ldp	xzr, x19, [sp], #16
+#ifdef KMSAN
+	mov	x0, x19
+	mov	x1, #(ARM_SMCCC_1_2_REGS_SIZE)
+	mov	x2, #(KMSAN_STATE_INITED)
+	bl	kmsan_mark
+	/* Restore x0 as the return value */
+	ldr	x0, [x19]
+#endif
+1:
+	ldr	     x19, [sp, #24]
+	ldp	x29, x30, [sp], #32
 	ret
+#ifdef KMSAN
+.Lfunc_name_\insn:
+	.asciz	"arm_smccc_1_2_\insn"
+#endif
 END(arm_smccc_1_2_\insn)
 .endm
 /* int arm_smccc_1_2_*(const struct arm_smccc_1_2_regs *args,