In the process of creating the user-facing flags in
register_generic_cpu_props() we're also setting default values for the
cpu->cfg flags that represents MISA bits.

Leaving it as is will cause a discrepancy between users of this function
(at this moment the non-named CPUs) and named CPUs. Named CPUs are using
set_misa() with a non-zero 'ext' value, writing cpu->cfg in the process.
They'll reach riscv_cpu_realize() in a state where env->misa_ext will
reflect cpu->cfg, allowing functions to choose whether to use
env->misa_ext or cpu->cfg to validate MISA bits.

If we guarantee that env->misa_ext will always reflect cpu->cfg at the
start of riscv_cpu_realize(), functions will be able to no longer rely
on cpu->cfg for MISA validation. This happens to be one blocker we have
to properly support write_misa().

Sync env->misa_ext* in register_generic_cpu_props(). After that, there
will be no more places where env->misa_ext needs to be sync back with
cpu->cfg, so remove the now obsolete code at the end of
riscv_cpu_validate_set_extensions().

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index d8f2eca6ca..992edd1735 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1116,14 +1116,10 @@ static void riscv_cpu_validate_misa_mxl(RISCVCPU *cpu, Error **errp)
 
 /*
  * Check consistency between chosen extensions while setting
- * cpu->cfg accordingly, setting env->misa_ext and
- * misa_ext_mask in the end.
+ * cpu->cfg accordingly.
  */
 static void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
 {
-    CPURISCVState *env = &cpu->env;
-    uint32_t ext = 0;
-
     if (cpu->cfg.epmp && !cpu->cfg.pmp) {
         /*
          * Enhanced PMP should only be available
@@ -1240,10 +1236,6 @@ static void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
      * validated and set everything we need.
      */
     riscv_cpu_disable_priv_spec_isa_exts(cpu);
-
-    ext = riscv_get_misa_ext_with_cpucfg(&cpu->cfg);
-
-    env->misa_ext_mask = env->misa_ext = ext;
 }
 
 #ifndef CONFIG_USER_ONLY
@@ -1354,6 +1346,10 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+    /*
+     * This is the last point where env->misa_ext* can
+     * be changed.
+     */
     if (cpu->cfg.ext_g) {
         riscv_cpu_enable_g(cpu, &local_err);
         if (local_err != NULL) {
@@ -1631,10 +1627,12 @@ static Property riscv_cpu_extensions[] = {
  * Register generic CPU props with user-facing flags declared
  * in riscv_cpu_extensions[].
  *
- * Note that this will overwrite existing values in cpu->cfg.
+ * Note that this will overwrite existing values in cpu->cfg
+ * and MISA.
  */
 static void register_generic_cpu_props(Object *obj)
 {
+    RISCVCPU *cpu = RISCV_CPU(obj);
     Property *prop;
     DeviceState *dev = DEVICE(obj);
 
@@ -1645,6 +1643,10 @@ static void register_generic_cpu_props(Object *obj)
 #ifndef CONFIG_USER_ONLY
     riscv_add_satp_mode_properties(obj);
 #endif
+
+    /* Keep env->misa_ext and misa_ext_mask updated */
+    cpu->env.misa_ext = riscv_get_misa_ext_with_cpucfg(&cpu->cfg);
+    cpu->env.misa_ext_mask = cpu->env.misa_ext;
 }
 
 static Property riscv_cpu_properties[] = {
-- 
2.39.2