target/riscv/cpu.c: do better with 'named features' doc

Most of the named features are added directly in isa_edata_arr[], some
of them are also added in riscv_cpu_named_features(). There is a reason
for that, and the existing docs can do better explaining it.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20250529202315.1684198-4-dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250604174329.1147549-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -1377,13 +1377,23 @@ const RISCVCPUMultiExtConfig riscv_cpu_experimental_exts[] = {
  * 'Named features' is the name we give to extensions that we
  * don't want to expose to users. They are either immutable
  * (always enabled/disable) or they'll vary depending on
- * the resulting CPU state. They have riscv,isa strings
- * and priv_ver like regular extensions.
+ * the resulting CPU state.
+ *
+ * Some of them are always enabled depending on priv version
+ * of the CPU and are declared directly in isa_edata_arr[].
+ * The ones listed here have special checks during finalize()
+ * time and require their own flags like regular extensions.
+ * See riscv_cpu_update_named_features() for more info.
  */
 const RISCVCPUMultiExtConfig riscv_cpu_named_features[] = {
     MULTI_EXT_CFG_BOOL("zic64b", ext_zic64b, true),
     MULTI_EXT_CFG_BOOL("ssstateen", ext_ssstateen, true),
     MULTI_EXT_CFG_BOOL("sha", ext_sha, true),
+
+    /*
+     * 'ziccrse' has its own flag because the KVM driver
+     * wants to enable/disable it on its own accord.
+     */
     MULTI_EXT_CFG_BOOL("ziccrse", ext_ziccrse, true),
 
     { },