target/riscv: Allow setting CPU feature from machine/device emulation

The machine or device emulation should be able to force set certain
CPU features because:
1) We can have certain CPU features which are in-general optional
   but implemented by RISC-V CPUs on the machine.
2) We can have devices which require a certain CPU feature. For example,
   AIA IMSIC devices expect AIA CSRs implemented by RISC-V CPUs.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Message-id: 20220204174700.534953-6-anup@brainfault.org
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -135,11 +135,6 @@ static void set_vext_version(CPURISCVState *env, int vext_ver)
     env->vext_ver = vext_ver;
 }
 
-static void set_feature(CPURISCVState *env, int feature)
-{
-    env->features |= (1ULL << feature);
-}
-
 static void set_resetvec(CPURISCVState *env, target_ulong resetvec)
 {
 #ifndef CONFIG_USER_ONLY
@@ -508,18 +503,18 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
     }
 
     if (cpu->cfg.mmu) {
-        set_feature(env, RISCV_FEATURE_MMU);
+        riscv_set_feature(env, RISCV_FEATURE_MMU);
     }
 
     if (cpu->cfg.pmp) {
-        set_feature(env, RISCV_FEATURE_PMP);
+        riscv_set_feature(env, RISCV_FEATURE_PMP);
 
         /*
          * Enhanced PMP should only be available
          * on harts with PMP support
          */
         if (cpu->cfg.epmp) {
-            set_feature(env, RISCV_FEATURE_EPMP);
+            riscv_set_feature(env, RISCV_FEATURE_EPMP);
         }
     }
 

target/riscv/cpu.h

@@ -379,6 +379,11 @@ static inline bool riscv_feature(CPURISCVState *env, int feature)
     return env->features & (1ULL << feature);
 }
 
+static inline void riscv_set_feature(CPURISCVState *env, int feature)
+{
+    env->features |= (1ULL << feature);
+}
+
 #include "cpu_user.h"
 
 extern const char * const riscv_int_regnames[];