diff --git a/include/sbi/riscv_encoding.h b/include/sbi/riscv_encoding.h
index 3c1d5256..18f7b4a7 100644
--- a/include/sbi/riscv_encoding.h
+++ b/include/sbi/riscv_encoding.h
@@ -215,6 +215,10 @@
 
 #endif
 
+#define MNSTATUS_NMIE			(_UL(0x8))
+#define MNSTATUS_MNPV			(_UL(0x80))
+#define MNSTATUS_MNPP			(_UL(0x1800))
+
 #define MHPMEVENT_SSCOF_MASK		_ULL(0xFF00000000000000)
 
 #define ENVCFG_STCE			(_ULL(1) << 63)
@@ -830,6 +834,12 @@
 #define CSR_CUSTOM10_M_RO_BASE		0xFC0
 #define CSR_CUSTOM10_M_RO_COUNT		0x040
 
+/* Smrnmi extension registers */
+#define CSR_MNSCRATCH				0x740
+#define CSR_MNEPC					0x741
+#define CSR_MNCAUSE					0x742
+#define CSR_MNSTATUS				0x744
+
 /* ===== Trap/Exception Causes ===== */
 
 #define CAUSE_MISALIGNED_FETCH		0x0
diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index a788b34c..937cdf29 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -87,6 +87,8 @@ enum sbi_hart_extensions {
 	SBI_HART_EXT_XSIFIVE_CFLUSH_D_L1,
 	/** Hart has Xsfcease extension */
 	SBI_HART_EXT_XSIFIVE_CEASE,
+	/** Hart has Smrnmi extension */
+	SBI_HART_EXT_SMRNMI,
 
 	/** Maximum index of Hart extension */
 	SBI_HART_EXT_MAX,
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 99e13990..4aefb759 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -396,6 +396,7 @@ const struct sbi_hart_ext_data sbi_hart_ext[] = {
 	__SBI_HART_EXT_DATA(ssstateen, SBI_HART_EXT_SSSTATEEN),
 	__SBI_HART_EXT_DATA(xsfcflushdlone, SBI_HART_EXT_XSIFIVE_CFLUSH_D_L1),
 	__SBI_HART_EXT_DATA(xsfcease, SBI_HART_EXT_XSIFIVE_CEASE),
+	__SBI_HART_EXT_DATA(smrnmi, SBI_HART_EXT_SMRNMI),
 };
 
 _Static_assert(SBI_HART_EXT_MAX == array_size(sbi_hart_ext),