diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
index affe700..f3f9f9f 100644
--- a/arch/riscv/cpu/cpu.c
+++ b/arch/riscv/cpu/cpu.c
@@ -14,8 +14,12 @@
 #include <log.h>
 #include <asm/encoding.h>
 #include <asm/system.h>
+#include <asm/hwcap.h>
+#include <asm/cpufeature.h>
 #include <dm/uclass-internal.h>
 #include <linux/bitops.h>
+#include <linux/log2.h>
+#include <linux/ctype.h>
 
 /*
  * The variables here must be stored in the data section since they are used
@@ -33,6 +37,559 @@
 #endif
 #endif
 
+/* Host ISA bitmap */
+static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __section(".data");
+
+static unsigned int riscv_cbom_block_size __section(".data");
+static unsigned int riscv_cboz_block_size __section(".data");
+/**
+ * __riscv_isa_extension_available() - Check whether given extension
+ * is available or not
+ *
+ * @bit: bit position of the desired extension
+ * Return: true or false
+ *
+ */
+static bool __riscv_isa_extension_available(unsigned int bit)
+{
+	if (bit >= RISCV_ISA_EXT_MAX)
+		return false;
+
+	return test_bit(bit, riscv_isa) ? true : false;
+}
+
+inline unsigned int riscv_get_cbom_block_size(void)
+{
+	return riscv_cbom_block_size;
+}
+
+inline unsigned int riscv_get_cboz_block_size(void)
+{
+	return riscv_cboz_block_size;
+}
+
+static int riscv_ext_zicbom_validate(const struct riscv_isa_ext_data *data,
+				     const unsigned long *isa_bitmap)
+{
+	struct udevice *dev;
+
+	if (!CONFIG_IS_ENABLED(RISCV_ISA_ZICBOM) || riscv_cbom_block_size)
+		return 0;
+
+	uclass_first_device(UCLASS_CPU, &dev);
+	if (!dev) {
+		log_info("Failed to get cpu device!\n");
+		return -ENXIO;
+	}
+
+	if (!dev_read_u32(dev, "riscv,cbom-block-size",
+			  &riscv_cbom_block_size)) {
+		if (!riscv_cbom_block_size) {
+			log_err("Zicbom detected in ISA string, disabling as no cbom-block-size found\n");
+			return -EINVAL;
+		}
+		if (!is_power_of_2(riscv_cbom_block_size)) {
+			log_err("Zicbom disabled as cbom-block-size present, but is not a power-of-2\n");
+			return -EINVAL;
+		}
+		return 0;
+	} else {
+		return -EINVAL;
+	}
+}
+
+static int riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
+				     const unsigned long *isa_bitmap)
+{
+	struct udevice *dev;
+
+	if (!CONFIG_IS_ENABLED(RISCV_ISA_ZICBOM) || riscv_cboz_block_size)
+		return 0;
+
+	uclass_first_device(UCLASS_CPU, &dev);
+	if (!dev) {
+		log_debug("Failed to get cpu device!\n");
+		return -ENXIO;
+	}
+
+	if (!dev_read_u32(dev, "riscv,cboz-block-size",
+			  &riscv_cboz_block_size)) {
+		if (!riscv_cboz_block_size) {
+			log_err("Zicboz detected in ISA string, disabling as no cboz-block-size found\n");
+			return -EINVAL;
+		}
+		if (!is_power_of_2(riscv_cboz_block_size)) {
+			log_err("Zicboz disabled as cboz-block-size present, but is not a power-of-2\n");
+			return -EINVAL;
+		}
+		return 0;
+	} else {
+		return -EINVAL;
+	}
+}
+
+static int riscv_ext_zca_depends(const struct riscv_isa_ext_data *data,
+				 const unsigned long *isa_bitmap)
+{
+	if (__riscv_isa_extension_available(RISCV_ISA_EXT_ZCA))
+		return 0;
+
+	return -EINVAL;
+}
+
+static int riscv_ext_zcd_validate(const struct riscv_isa_ext_data *data,
+				  const unsigned long *isa_bitmap)
+{
+	if (__riscv_isa_extension_available(RISCV_ISA_EXT_ZCA) &&
+	    __riscv_isa_extension_available(RISCV_ISA_EXT_d))
+		return 0;
+
+	return -EINVAL;
+}
+
+static int riscv_ext_zcf_validate(const struct riscv_isa_ext_data *data,
+				  const unsigned long *isa_bitmap)
+{
+	if (IS_ENABLED(CONFIG_64BIT))
+		return -EINVAL;
+
+	if (__riscv_isa_extension_available(RISCV_ISA_EXT_ZCA) &&
+	    __riscv_isa_extension_available(RISCV_ISA_EXT_f))
+		return 0;
+
+	return -EINVAL;
+}
+
+static const unsigned int riscv_zk_bundled_exts[] = {
+	RISCV_ISA_EXT_ZBKB,
+	RISCV_ISA_EXT_ZBKC,
+	RISCV_ISA_EXT_ZBKX,
+	RISCV_ISA_EXT_ZKND,
+	RISCV_ISA_EXT_ZKNE,
+	RISCV_ISA_EXT_ZKR,
+	RISCV_ISA_EXT_ZKT,
+};
+
+static const unsigned int riscv_zkn_bundled_exts[] = {
+	RISCV_ISA_EXT_ZBKB,
+	RISCV_ISA_EXT_ZBKC,
+	RISCV_ISA_EXT_ZBKX,
+	RISCV_ISA_EXT_ZKND,
+	RISCV_ISA_EXT_ZKNE,
+	RISCV_ISA_EXT_ZKNH,
+};
+
+static const unsigned int riscv_zks_bundled_exts[] = {
+	RISCV_ISA_EXT_ZBKB,
+	RISCV_ISA_EXT_ZBKC,
+	RISCV_ISA_EXT_ZKSED,
+	RISCV_ISA_EXT_ZKSH
+};
+
+#define RISCV_ISA_EXT_ZVKN	\
+	RISCV_ISA_EXT_ZVKNED,	\
+	RISCV_ISA_EXT_ZVKNHB,	\
+	RISCV_ISA_EXT_ZVKB,	\
+	RISCV_ISA_EXT_ZVKT
+
+static const unsigned int riscv_zvkn_bundled_exts[] = {
+	RISCV_ISA_EXT_ZVKN
+};
+
+static const unsigned int riscv_zvknc_bundled_exts[] = {
+	RISCV_ISA_EXT_ZVKN,
+	RISCV_ISA_EXT_ZVBC
+};
+
+static const unsigned int riscv_zvkng_bundled_exts[] = {
+	RISCV_ISA_EXT_ZVKN,
+	RISCV_ISA_EXT_ZVKG
+};
+
+#define RISCV_ISA_EXT_ZVKS	\
+	RISCV_ISA_EXT_ZVKSED,	\
+	RISCV_ISA_EXT_ZVKSH,	\
+	RISCV_ISA_EXT_ZVKB,	\
+	RISCV_ISA_EXT_ZVKT
+
+static const unsigned int riscv_zvks_bundled_exts[] = {
+	RISCV_ISA_EXT_ZVKS
+};
+
+static const unsigned int riscv_zvksc_bundled_exts[] = {
+	RISCV_ISA_EXT_ZVKS,
+	RISCV_ISA_EXT_ZVBC
+};
+
+static const unsigned int riscv_zvksg_bundled_exts[] = {
+	RISCV_ISA_EXT_ZVKS,
+	RISCV_ISA_EXT_ZVKG
+};
+
+static const unsigned int riscv_zvbb_exts[] = {
+	RISCV_ISA_EXT_ZVKB
+};
+
+#define RISCV_ISA_EXT_ZVE64F_IMPLY_LIST	\
+	RISCV_ISA_EXT_ZVE64X,		\
+	RISCV_ISA_EXT_ZVE32F,		\
+	RISCV_ISA_EXT_ZVE32X
+
+#define RISCV_ISA_EXT_ZVE64D_IMPLY_LIST	\
+	RISCV_ISA_EXT_ZVE64F,		\
+	RISCV_ISA_EXT_ZVE64F_IMPLY_LIST
+
+#define RISCV_ISA_EXT_V_IMPLY_LIST	\
+	RISCV_ISA_EXT_ZVE64D,		\
+	RISCV_ISA_EXT_ZVE64D_IMPLY_LIST
+
+static const unsigned int riscv_zve32f_exts[] = {
+	RISCV_ISA_EXT_ZVE32X
+};
+
+static const unsigned int riscv_zve64f_exts[] = {
+	RISCV_ISA_EXT_ZVE64F_IMPLY_LIST
+};
+
+static const unsigned int riscv_zve64d_exts[] = {
+	RISCV_ISA_EXT_ZVE64D_IMPLY_LIST
+};
+
+static const unsigned int riscv_v_exts[] = {
+	RISCV_ISA_EXT_V_IMPLY_LIST
+};
+
+static const unsigned int riscv_zve64x_exts[] = {
+	RISCV_ISA_EXT_ZVE32X,
+	RISCV_ISA_EXT_ZVE64X
+};
+
+/*
+ * While the [ms]envcfg CSRs were not defined until version 1.12 of the RISC-V
+ * privileged ISA, the existence of the CSRs is implied by any extension which
+ * specifies [ms]envcfg bit(s). Hence, we define a custom ISA extension for the
+ * existence of the CSR, and treat it as a subset of those other extensions.
+ */
+static const unsigned int riscv_xlinuxenvcfg_exts[] = {
+	RISCV_ISA_EXT_XLINUXENVCFG
+};
+
+/*
+ * Zc* spec states that:
+ * - C always implies Zca
+ * - C+F implies Zcf (RV32 only)
+ * - C+D implies Zcd
+ *
+ * These extensions will be enabled and then validated depending on the
+ * availability of F/D RV32.
+ */
+static const unsigned int riscv_c_exts[] = {
+	RISCV_ISA_EXT_ZCA,
+	RISCV_ISA_EXT_ZCF,
+	RISCV_ISA_EXT_ZCD,
+};
+
+/*
+ * The canonical order of ISA extension names in the ISA string is defined in
+ * chapter 27 of the unprivileged specification.
+ *
+ * Ordinarily, for in-kernel data structures, this order is unimportant but
+ * isa_ext_arr defines the order of the ISA string in /proc/cpuinfo.
+ *
+ * The specification uses vague wording, such as should, when it comes to
+ * ordering, so for our purposes the following rules apply:
+ *
+ * 1. All multi-letter extensions must be separated from other extensions by an
+ *    underscore.
+ *
+ * 2. Additional standard extensions (starting with 'Z') must be sorted after
+ *    single-letter extensions and before any higher-privileged extensions.
+ *
+ * 3. The first letter following the 'Z' conventionally indicates the most
+ *    closely related alphabetical extension category, IMAFDQLCBKJTPVH.
+ *    If multiple 'Z' extensions are named, they must be ordered first by
+ *    category, then alphabetically within a category.
+ *
+ * 3. Standard supervisor-level extensions (starting with 'S') must be listed
+ *    after standard unprivileged extensions.  If multiple supervisor-level
+ *    extensions are listed, they must be ordered alphabetically.
+ *
+ * 4. Standard machine-level extensions (starting with 'Zxm') must be listed
+ *    after any lower-privileged, standard extensions.  If multiple
+ *    machine-level extensions are listed, they must be ordered
+ *    alphabetically.
+ *
+ * 5. Non-standard extensions (starting with 'X') must be listed after all
+ *    standard extensions. If multiple non-standard extensions are listed, they
+ *    must be ordered alphabetically.
+ *
+ * An example string following the order is:
+ *    rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux
+ *
+ * New entries to this struct should follow the ordering rules described above.
+ */
+const struct riscv_isa_ext_data riscv_isa_ext[] = {
+	__RISCV_ISA_EXT_DATA(i, RISCV_ISA_EXT_i),
+	__RISCV_ISA_EXT_DATA(m, RISCV_ISA_EXT_m),
+	__RISCV_ISA_EXT_DATA(a, RISCV_ISA_EXT_a),
+	__RISCV_ISA_EXT_DATA(f, RISCV_ISA_EXT_f),
+	__RISCV_ISA_EXT_DATA(d, RISCV_ISA_EXT_d),
+	__RISCV_ISA_EXT_DATA(q, RISCV_ISA_EXT_q),
+	__RISCV_ISA_EXT_SUPERSET(c, RISCV_ISA_EXT_c, riscv_c_exts),
+	__RISCV_ISA_EXT_SUPERSET(v, RISCV_ISA_EXT_v, riscv_v_exts),
+	__RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h),
+	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts,
+					  riscv_ext_zicbom_validate),
+	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts,
+					  riscv_ext_zicboz_validate),
+	__RISCV_ISA_EXT_DATA(zicntr, RISCV_ISA_EXT_ZICNTR),
+	__RISCV_ISA_EXT_DATA(zicond, RISCV_ISA_EXT_ZICOND),
+	__RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),
+	__RISCV_ISA_EXT_DATA(zifencei, RISCV_ISA_EXT_ZIFENCEI),
+	__RISCV_ISA_EXT_DATA(zihintntl, RISCV_ISA_EXT_ZIHINTNTL),
+	__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
+	__RISCV_ISA_EXT_DATA(zihpm, RISCV_ISA_EXT_ZIHPM),
+	__RISCV_ISA_EXT_DATA(zimop, RISCV_ISA_EXT_ZIMOP),
+	__RISCV_ISA_EXT_DATA(zacas, RISCV_ISA_EXT_ZACAS),
+	__RISCV_ISA_EXT_DATA(zawrs, RISCV_ISA_EXT_ZAWRS),
+	__RISCV_ISA_EXT_DATA(zfa, RISCV_ISA_EXT_ZFA),
+	__RISCV_ISA_EXT_DATA(zfh, RISCV_ISA_EXT_ZFH),
+	__RISCV_ISA_EXT_DATA(zfhmin, RISCV_ISA_EXT_ZFHMIN),
+	__RISCV_ISA_EXT_DATA(zca, RISCV_ISA_EXT_ZCA),
+	__RISCV_ISA_EXT_DATA_VALIDATE(zcb, RISCV_ISA_EXT_ZCB, riscv_ext_zca_depends),
+	__RISCV_ISA_EXT_DATA_VALIDATE(zcd, RISCV_ISA_EXT_ZCD, riscv_ext_zcd_validate),
+	__RISCV_ISA_EXT_DATA_VALIDATE(zcf, RISCV_ISA_EXT_ZCF, riscv_ext_zcf_validate),
+	__RISCV_ISA_EXT_DATA_VALIDATE(zcmop, RISCV_ISA_EXT_ZCMOP, riscv_ext_zca_depends),
+	__RISCV_ISA_EXT_DATA(zba, RISCV_ISA_EXT_ZBA),
+	__RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
+	__RISCV_ISA_EXT_DATA(zbc, RISCV_ISA_EXT_ZBC),
+	__RISCV_ISA_EXT_DATA(zbkb, RISCV_ISA_EXT_ZBKB),
+	__RISCV_ISA_EXT_DATA(zbkc, RISCV_ISA_EXT_ZBKC),
+	__RISCV_ISA_EXT_DATA(zbkx, RISCV_ISA_EXT_ZBKX),
+	__RISCV_ISA_EXT_DATA(zbs, RISCV_ISA_EXT_ZBS),
+	__RISCV_ISA_EXT_BUNDLE(zk, riscv_zk_bundled_exts),
+	__RISCV_ISA_EXT_BUNDLE(zkn, riscv_zkn_bundled_exts),
+	__RISCV_ISA_EXT_DATA(zknd, RISCV_ISA_EXT_ZKND),
+	__RISCV_ISA_EXT_DATA(zkne, RISCV_ISA_EXT_ZKNE),
+	__RISCV_ISA_EXT_DATA(zknh, RISCV_ISA_EXT_ZKNH),
+	__RISCV_ISA_EXT_DATA(zkr, RISCV_ISA_EXT_ZKR),
+	__RISCV_ISA_EXT_BUNDLE(zks, riscv_zks_bundled_exts),
+	__RISCV_ISA_EXT_DATA(zkt, RISCV_ISA_EXT_ZKT),
+	__RISCV_ISA_EXT_DATA(zksed, RISCV_ISA_EXT_ZKSED),
+	__RISCV_ISA_EXT_DATA(zksh, RISCV_ISA_EXT_ZKSH),
+	__RISCV_ISA_EXT_DATA(ztso, RISCV_ISA_EXT_ZTSO),
+	__RISCV_ISA_EXT_SUPERSET(zvbb, RISCV_ISA_EXT_ZVBB, riscv_zvbb_exts),
+	__RISCV_ISA_EXT_DATA(zvbc, RISCV_ISA_EXT_ZVBC),
+	__RISCV_ISA_EXT_SUPERSET(zve32f, RISCV_ISA_EXT_ZVE32F, riscv_zve32f_exts),
+	__RISCV_ISA_EXT_DATA(zve32x, RISCV_ISA_EXT_ZVE32X),
+	__RISCV_ISA_EXT_SUPERSET(zve64d, RISCV_ISA_EXT_ZVE64D, riscv_zve64d_exts),
+	__RISCV_ISA_EXT_SUPERSET(zve64f, RISCV_ISA_EXT_ZVE64F, riscv_zve64f_exts),
+	__RISCV_ISA_EXT_SUPERSET(zve64x, RISCV_ISA_EXT_ZVE64X, riscv_zve64x_exts),
+	__RISCV_ISA_EXT_DATA(zvfh, RISCV_ISA_EXT_ZVFH),
+	__RISCV_ISA_EXT_DATA(zvfhmin, RISCV_ISA_EXT_ZVFHMIN),
+	__RISCV_ISA_EXT_DATA(zvkb, RISCV_ISA_EXT_ZVKB),
+	__RISCV_ISA_EXT_DATA(zvkg, RISCV_ISA_EXT_ZVKG),
+	__RISCV_ISA_EXT_BUNDLE(zvkn, riscv_zvkn_bundled_exts),
+	__RISCV_ISA_EXT_BUNDLE(zvknc, riscv_zvknc_bundled_exts),
+	__RISCV_ISA_EXT_DATA(zvkned, RISCV_ISA_EXT_ZVKNED),
+	__RISCV_ISA_EXT_BUNDLE(zvkng, riscv_zvkng_bundled_exts),
+	__RISCV_ISA_EXT_DATA(zvknha, RISCV_ISA_EXT_ZVKNHA),
+	__RISCV_ISA_EXT_DATA(zvknhb, RISCV_ISA_EXT_ZVKNHB),
+	__RISCV_ISA_EXT_BUNDLE(zvks, riscv_zvks_bundled_exts),
+	__RISCV_ISA_EXT_BUNDLE(zvksc, riscv_zvksc_bundled_exts),
+	__RISCV_ISA_EXT_DATA(zvksed, RISCV_ISA_EXT_ZVKSED),
+	__RISCV_ISA_EXT_DATA(zvksh, RISCV_ISA_EXT_ZVKSH),
+	__RISCV_ISA_EXT_BUNDLE(zvksg, riscv_zvksg_bundled_exts),
+	__RISCV_ISA_EXT_DATA(zvkt, RISCV_ISA_EXT_ZVKT),
+	__RISCV_ISA_EXT_DATA(smaia, RISCV_ISA_EXT_SMAIA),
+	__RISCV_ISA_EXT_DATA(smmpm, RISCV_ISA_EXT_SMMPM),
+	__RISCV_ISA_EXT_SUPERSET(smnpm, RISCV_ISA_EXT_SMNPM, riscv_xlinuxenvcfg_exts),
+	__RISCV_ISA_EXT_DATA(smstateen, RISCV_ISA_EXT_SMSTATEEN),
+	__RISCV_ISA_EXT_DATA(ssaia, RISCV_ISA_EXT_SSAIA),
+	__RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),
+	__RISCV_ISA_EXT_SUPERSET(ssnpm, RISCV_ISA_EXT_SSNPM, riscv_xlinuxenvcfg_exts),
+	__RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC),
+	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
+	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
+	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
+	__RISCV_ISA_EXT_DATA(svvptc, RISCV_ISA_EXT_SVVPTC),
+};
+
+const size_t riscv_isa_ext_count = ARRAY_SIZE(riscv_isa_ext);
+
+static void riscv_isa_set_ext(const struct riscv_isa_ext_data *ext, unsigned long *bitmap)
+{
+	if (ext->id != RISCV_ISA_EXT_INVALID)
+		__set_bit(ext->id, bitmap);
+
+	for (int i = 0; i < ext->subset_ext_size; i++) {
+		if (ext->subset_ext_ids[i] != RISCV_ISA_EXT_INVALID)
+			__set_bit(ext->subset_ext_ids[i], bitmap);
+	}
+}
+
+static void match_isa_ext(const char *name, const char *name_end)
+{
+	for (int i = 0; i < riscv_isa_ext_count; i++) {
+		const struct riscv_isa_ext_data *ext = &riscv_isa_ext[i];
+
+		if ((name_end - name == strlen(ext->name)) &&
+		    !strncasecmp(name, ext->name, name_end - name)) {
+			if (ext->validate && !ext->validate(ext, riscv_isa))
+				riscv_isa_set_ext(ext, riscv_isa);
+			break;
+		}
+	}
+}
+
+static void riscv_parse_isa_string(const char *isa)
+{
+	/*
+	 * For all possible cpus, we have already validated in
+	 * the boot process that they at least contain "rv" and
+	 * whichever of "32"/"64" this kernel supports, and so this
+	 * section can be skipped.
+	 */
+	isa += 4;
+
+	while (*isa) {
+		const char *ext = isa++;
+		const char *ext_end = isa;
+		bool ext_err = false;
+
+		switch (*ext) {
+		case 'x':
+		case 'X':
+			log_warning("Vendor extensions are ignored in riscv,isa. Use riscv,isa-extensions instead.");
+			/*
+			 * To skip an extension, we find its end.
+			 * As multi-letter extensions must be split from other multi-letter
+			 * extensions with an "_", the end of a multi-letter extension will
+			 * either be the null character or the "_" at the start of the next
+			 * multi-letter extension.
+			 */
+			for (; *isa && *isa != '_'; ++isa)
+				;
+			ext_err = true;
+			break;
+		case 's':
+			/*
+			 * Workaround for invalid single-letter 's' & 'u' (QEMU).
+			 * No need to set the bit in riscv_isa as 's' & 'u' are
+			 * not valid ISA extensions. It works unless the first
+			 * multi-letter extension in the ISA string begins with
+			 * "Su" and is not prefixed with an underscore.
+			 */
+			if (ext[-1] != '_' && ext[1] == 'u') {
+				++isa;
+				ext_err = true;
+				break;
+			}
+			fallthrough;
+		case 'S':
+		case 'z':
+		case 'Z':
+			/*
+			 * Before attempting to parse the extension itself, we find its end.
+			 * As multi-letter extensions must be split from other multi-letter
+			 * extensions with an "_", the end of a multi-letter extension will
+			 * either be the null character or the "_" at the start of the next
+			 * multi-letter extension.
+			 *
+			 * Next, as the extensions version is currently ignored, we
+			 * eliminate that portion. This is done by parsing backwards from
+			 * the end of the extension, removing any numbers. This may be a
+			 * major or minor number however, so the process is repeated if a
+			 * minor number was found.
+			 *
+			 * ext_end is intended to represent the first character *after* the
+			 * name portion of an extension, but will be decremented to the last
+			 * character itself while eliminating the extensions version number.
+			 * A simple re-increment solves this problem.
+			 */
+			for (; *isa && *isa != '_'; ++isa)
+				if (unlikely(!isalnum(*isa)))
+					ext_err = true;
+
+			ext_end = isa;
+			if (unlikely(ext_err))
+				break;
+
+			if (!isdigit(ext_end[-1]))
+				break;
+
+			while (isdigit(*--ext_end))
+				;
+
+			if (tolower(ext_end[0]) != 'p' || !isdigit(ext_end[-1])) {
+				++ext_end;
+				break;
+			}
+
+			while (isdigit(*--ext_end))
+				;
+
+			++ext_end;
+			break;
+		default:
+			/*
+			 * Things are a little easier for single-letter extensions, as they
+			 * are parsed forwards.
+			 *
+			 * After checking that our starting position is valid, we need to
+			 * ensure that, when isa was incremented at the start of the loop,
+			 * that it arrived at the start of the next extension.
+			 *
+			 * If we are already on a non-digit, there is nothing to do. Either
+			 * we have a multi-letter extension's _, or the start of an
+			 * extension.
+			 *
+			 * Otherwise we have found the current extension's major version
+			 * number. Parse past it, and a subsequent p/minor version number
+			 * if present. The `p` extension must not appear immediately after
+			 * a number, so there is no fear of missing it.
+			 *
+			 */
+			if (unlikely(!isalpha(*ext))) {
+				ext_err = true;
+				break;
+			}
+
+			if (!isdigit(*isa))
+				break;
+
+			while (isdigit(*++isa))
+				;
+
+			if (tolower(*isa) != 'p')
+				break;
+
+			if (!isdigit(*++isa)) {
+				--isa;
+				break;
+			}
+
+			while (isdigit(*++isa))
+				;
+
+			break;
+		}
+
+		/*
+		 * The parser expects that at the start of an iteration isa points to the
+		 * first character of the next extension. As we stop parsing an extension
+		 * on meeting a non-alphanumeric character, an extra increment is needed
+		 * where the succeeding extension is a multi-letter prefixed with an "_".
+		 */
+		if (*isa == '_')
+			++isa;
+
+		if (unlikely(ext_err))
+			continue;
+		match_isa_ext(ext, ext_end);
+	}
+}
+
 static inline bool supports_extension(char ext)
 {
 #if CONFIG_IS_ENABLED(RISCV_MMODE)