diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
index 61a4100..c97f09d 100644
--- a/lib/utils/fdt/fdt_helper.c
+++ b/lib/utils/fdt/fdt_helper.c
@@ -314,54 +314,14 @@ int fdt_parse_timebase_frequency(void *fdt, unsigned long *freq)
 	return 0;
 }
 
-static int fdt_get_isa_string(void *fdt, unsigned int hartid,
-			const char **isa_string)
-{
-	int err, cpu_offset, cpus_offset, len;
-	u32 c_hartid;
-	const fdt32_t *val;
-
-	if (!fdt)
-		return SBI_EINVAL;
-
-	cpus_offset = fdt_path_offset(fdt, "/cpus");
-	if (cpus_offset < 0)
-		return cpus_offset;
-
-	fdt_for_each_subnode(cpu_offset, fdt, cpus_offset) {
-		err = fdt_parse_hart_id(fdt, cpu_offset, &c_hartid);
-		if (err)
-			continue;
-
-		if (!fdt_node_is_enabled(fdt, cpu_offset))
-			continue;
-
-		if (c_hartid == hartid) {
-			val = fdt_getprop(fdt, cpu_offset, "riscv,isa", &len);
-			if (val && len > 0) {
-				*isa_string = (const char *)val;
-				return 0;
-			}
-		}
-	}
-
-	return SBI_EINVAL;
-}
-
 #define RISCV_ISA_EXT_NAME_LEN_MAX	32
 
-int fdt_parse_isa_extensions(void *fdt, unsigned int hartid,
-			unsigned long *extensions)
+static unsigned long fdt_isa_bitmap_offset;
+
+static int fdt_parse_isa_one_hart(const char *isa, unsigned long *extensions)
 {
 	size_t i, j, isa_len;
 	char mstr[RISCV_ISA_EXT_NAME_LEN_MAX];
-	const char *isa = NULL;
-
-	if (fdt_get_isa_string(fdt, hartid, &isa))
-		return SBI_EINVAL;
-
-	if (!isa)
-		return SBI_EINVAL;
 
 	i = 0;
 	isa_len = strlen(isa);
@@ -424,6 +384,82 @@ int fdt_parse_isa_extensions(void *fdt, unsigned int hartid,
 	return 0;
 }
 
+static int fdt_parse_isa_all_harts(void *fdt)
+{
+	u32 hartid;
+	const fdt32_t *val;
+	unsigned long *hart_exts;
+	struct sbi_scratch *scratch;
+	int err, cpu_offset, cpus_offset, len;
+
+	if (!fdt || !fdt_isa_bitmap_offset)
+		return SBI_EINVAL;
+
+	cpus_offset = fdt_path_offset(fdt, "/cpus");
+	if (cpus_offset < 0)
+		return cpus_offset;
+
+	fdt_for_each_subnode(cpu_offset, fdt, cpus_offset) {
+		err = fdt_parse_hart_id(fdt, cpu_offset, &hartid);
+		if (err)
+			continue;
+
+		if (!fdt_node_is_enabled(fdt, cpu_offset))
+			continue;
+
+		val = fdt_getprop(fdt, cpu_offset, "riscv,isa", &len);
+		if (!val || len <= 0)
+			return SBI_ENOENT;
+
+		scratch = sbi_hartid_to_scratch(hartid);
+		if (!scratch)
+			return SBI_ENOENT;
+
+		hart_exts = sbi_scratch_offset_ptr(scratch,
+						   fdt_isa_bitmap_offset);
+		if (!hart_exts)
+			return SBI_ENOENT;
+
+		err = fdt_parse_isa_one_hart((const char *)val, hart_exts);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+int fdt_parse_isa_extensions(void *fdt, unsigned int hartid,
+			unsigned long *extensions)
+{
+	int rc, i;
+	unsigned long *hart_exts;
+	struct sbi_scratch *scratch;
+
+	if (!fdt_isa_bitmap_offset) {
+		fdt_isa_bitmap_offset = sbi_scratch_alloc_offset(
+					sizeof(*hart_exts) *
+					BITS_TO_LONGS(SBI_HART_EXT_MAX));
+		if (!fdt_isa_bitmap_offset)
+			return SBI_ENOMEM;
+
+		rc = fdt_parse_isa_all_harts(fdt);
+		if (rc)
+			return rc;
+	}
+
+	scratch = sbi_hartid_to_scratch(hartid);
+	if (!scratch)
+		return SBI_ENOENT;
+
+	hart_exts = sbi_scratch_offset_ptr(scratch, fdt_isa_bitmap_offset);
+	if (!hart_exts)
+		return SBI_ENOENT;
+
+	for (i = 0; i < BITS_TO_LONGS(SBI_HART_EXT_MAX); i++)
+		extensions[i] |= hart_exts[i];
+	return 0;
+}
+
 static int fdt_parse_uart_node_common(void *fdt, int nodeoffset,
 				      struct platform_uart_data *uart,
 				      unsigned long default_freq,