target/riscv/cpu.c: redesign register_cpu_props()

The function is now a no-op for all cpu_init() callers that are setting
a non-zero misa value in set_misa(), since it's no longer used to sync
cpu->cfg props with env->misa_ext bits. Remove it in those cases.

While we're at it, rename the function to match what it's actually
doing: create user properties to set/remove CPU extensions. Make a note
that it will overwrite env->misa_ext with the defaults set by each user
property.

Update the MISA bits comment in cpu.h as well.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230406180351.570807-21-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -228,7 +228,7 @@ static const char * const riscv_intr_names[] = {
     "reserved"
 };
 
-static void register_cpu_props(Object *obj);
+static void riscv_cpu_add_user_properties(Object *obj);
 
 const char *riscv_cpu_get_trap_name(target_ulong cause, bool async)
 {
@@ -356,7 +356,6 @@ static void riscv_any_cpu_init(Object *obj)
 #endif
 
     set_priv_version(env, PRIV_VERSION_1_12_0);
-    register_cpu_props(obj);
 }
 
 #if defined(TARGET_RISCV64)
@@ -365,7 +364,7 @@ static void rv64_base_cpu_init(Object *obj)
     CPURISCVState *env = &RISCV_CPU(obj)->env;
     /* We set this in the realise function */
     set_misa(env, MXL_RV64, 0);
-    register_cpu_props(obj);
+    riscv_cpu_add_user_properties(obj);
     /* Set latest version of privileged specification */
     set_priv_version(env, PRIV_VERSION_1_12_0);
 #ifndef CONFIG_USER_ONLY
@@ -377,7 +376,6 @@ static void rv64_sifive_u_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
     set_misa(env, MXL_RV64, RVI | RVM | RVA | RVF | RVD | RVC | RVS | RVU);
-    register_cpu_props(obj);
     set_priv_version(env, PRIV_VERSION_1_10_0);
 #ifndef CONFIG_USER_ONLY
     set_satp_mode_max_supported(RISCV_CPU(obj), VM_1_10_SV39);
@@ -390,7 +388,6 @@ static void rv64_sifive_e_cpu_init(Object *obj)
     RISCVCPU *cpu = RISCV_CPU(obj);
 
     set_misa(env, MXL_RV64, RVI | RVM | RVA | RVC | RVU);
-    register_cpu_props(obj);
     set_priv_version(env, PRIV_VERSION_1_10_0);
     cpu->cfg.mmu = false;
 #ifndef CONFIG_USER_ONLY
@@ -436,7 +433,7 @@ static void rv128_base_cpu_init(Object *obj)
     CPURISCVState *env = &RISCV_CPU(obj)->env;
     /* We set this in the realise function */
     set_misa(env, MXL_RV128, 0);
-    register_cpu_props(obj);
+    riscv_cpu_add_user_properties(obj);
     /* Set latest version of privileged specification */
     set_priv_version(env, PRIV_VERSION_1_12_0);
 #ifndef CONFIG_USER_ONLY
@@ -449,7 +446,7 @@ static void rv32_base_cpu_init(Object *obj)
     CPURISCVState *env = &RISCV_CPU(obj)->env;
     /* We set this in the realise function */
     set_misa(env, MXL_RV32, 0);
-    register_cpu_props(obj);
+    riscv_cpu_add_user_properties(obj);
     /* Set latest version of privileged specification */
     set_priv_version(env, PRIV_VERSION_1_12_0);
 #ifndef CONFIG_USER_ONLY
@@ -461,7 +458,6 @@ static void rv32_sifive_u_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
     set_misa(env, MXL_RV32, RVI | RVM | RVA | RVF | RVD | RVC | RVS | RVU);
-    register_cpu_props(obj);
     set_priv_version(env, PRIV_VERSION_1_10_0);
 #ifndef CONFIG_USER_ONLY
     set_satp_mode_max_supported(RISCV_CPU(obj), VM_1_10_SV32);
@@ -474,7 +470,6 @@ static void rv32_sifive_e_cpu_init(Object *obj)
     RISCVCPU *cpu = RISCV_CPU(obj);
 
     set_misa(env, MXL_RV32, RVI | RVM | RVA | RVC | RVU);
-    register_cpu_props(obj);
     set_priv_version(env, PRIV_VERSION_1_10_0);
     cpu->cfg.mmu = false;
 #ifndef CONFIG_USER_ONLY
@@ -488,7 +483,6 @@ static void rv32_ibex_cpu_init(Object *obj)
     RISCVCPU *cpu = RISCV_CPU(obj);
 
     set_misa(env, MXL_RV32, RVI | RVM | RVC | RVU);
-    register_cpu_props(obj);
     set_priv_version(env, PRIV_VERSION_1_11_0);
     cpu->cfg.mmu = false;
 #ifndef CONFIG_USER_ONLY
@@ -503,7 +497,6 @@ static void rv32_imafcu_nommu_cpu_init(Object *obj)
     RISCVCPU *cpu = RISCV_CPU(obj);
 
     set_misa(env, MXL_RV32, RVI | RVM | RVA | RVF | RVC | RVU);
-    register_cpu_props(obj);
     set_priv_version(env, PRIV_VERSION_1_10_0);
     cpu->cfg.mmu = false;
 #ifndef CONFIG_USER_ONLY
@@ -521,7 +514,7 @@ static void riscv_host_cpu_init(Object *obj)
 #elif defined(TARGET_RISCV64)
     set_misa(env, MXL_RV64, 0);
 #endif
-    register_cpu_props(obj);
+    riscv_cpu_add_user_properties(obj);
 }
 #endif
 
@@ -1577,30 +1570,16 @@ static Property riscv_cpu_extensions[] = {
 };
 
 /*
- * Register CPU props based on env.misa_ext. If a non-zero
+ * Add CPU properties with user-facing flags.
- * value was set, register only the required cpu->cfg.ext_*
+ *
- * properties and leave. env.misa_ext = 0 means that we want
+ * This will overwrite existing env->misa_ext values with the
- * all the default properties to be registered.
+ * defaults set via riscv_cpu_add_misa_properties().
  */
-static void register_cpu_props(Object *obj)
+static void riscv_cpu_add_user_properties(Object *obj)
 {
-    RISCVCPU *cpu = RISCV_CPU(obj);
     Property *prop;
     DeviceState *dev = DEVICE(obj);
 
-    /*
-     * If misa_ext is not zero, set cfg properties now to
-     * allow them to be read during riscv_cpu_realize()
-     * later on.
-     */
-    if (cpu->env.misa_ext != 0) {
-        /*
-         * We don't want to set the default riscv_cpu_extensions
-         * in this case.
-         */
-        return;
-    }
-
     riscv_cpu_add_misa_properties(obj);
 
     for (prop = riscv_cpu_extensions; prop && prop->name; prop++) {

target/riscv/cpu.h

@@ -65,10 +65,7 @@
 
 #define RV(x) ((target_ulong)1 << (x - 'A'))
 
-/*
+/* Consider updating misa_ext_cfgs[] when adding new MISA bits here */
- * Consider updating register_cpu_props() when adding
- * new MISA bits here.
- */
 #define RVI RV('I')
 #define RVE RV('E') /* E and I are mutually exclusive */
 #define RVM RV('M')