target/riscv: Make RLB/MML/MMWP bits writable only when Smepmp is ena…

…bled

RLB/MML/MMWP bits in mseccfg CSR are introduced by Smepmp extension.
So they can only be writable and set to 1s when cfg.epmp is true.
Then we also need't check on epmp in pmp_hart_has_privs_default().

Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230517091519.34439-6-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/pmp.c

@@ -243,30 +243,28 @@ static bool pmp_hart_has_privs_default(CPURISCVState *env, target_ulong addr,
 {
     bool ret;
 
-    if (riscv_cpu_cfg(env)->epmp) {
-        if (MSECCFG_MMWP_ISSET(env)) {
-            /*
-             * The Machine Mode Whitelist Policy (mseccfg.MMWP) is set
-             * so we default to deny all, even for M-mode.
-             */
+    if (MSECCFG_MMWP_ISSET(env)) {
+        /*
+         * The Machine Mode Whitelist Policy (mseccfg.MMWP) is set
+         * so we default to deny all, even for M-mode.
+         */
+        *allowed_privs = 0;
+        return false;
+    } else if (MSECCFG_MML_ISSET(env)) {
+        /*
+         * The Machine Mode Lockdown (mseccfg.MML) bit is set
+         * so we can only execute code in M-mode with an applicable
+         * rule. Other modes are disabled.
+         */
+        if (mode == PRV_M && !(privs & PMP_EXEC)) {
+            ret = true;
+            *allowed_privs = PMP_READ | PMP_WRITE;
+        } else {
+            ret = false;
             *allowed_privs = 0;
-            return false;
-        } else if (MSECCFG_MML_ISSET(env)) {
-            /*
-             * The Machine Mode Lockdown (mseccfg.MML) bit is set
-             * so we can only execute code in M-mode with an applicable
-             * rule. Other modes are disabled.
-             */
-            if (mode == PRV_M && !(privs & PMP_EXEC)) {
-                ret = true;
-                *allowed_privs = PMP_READ | PMP_WRITE;
-            } else {
-                ret = false;
-                *allowed_privs = 0;
-            }
-
-            return ret;
         }
+
+        return ret;
     }
 
     if (!riscv_cpu_cfg(env)->pmp || (mode == PRV_M)) {
@@ -580,8 +578,12 @@ void mseccfg_csr_write(CPURISCVState *env, target_ulong val)
         }
     }
 
-    /* Sticky bits */
-    val |= (env->mseccfg & (MSECCFG_MMWP | MSECCFG_MML));
+    if (riscv_cpu_cfg(env)->epmp) {
+        /* Sticky bits */
+        val |= (env->mseccfg & (MSECCFG_MMWP | MSECCFG_MML));
+    } else {
+        val &= ~(MSECCFG_MMWP | MSECCFG_MML | MSECCFG_RLB);
+    }
 
     env->mseccfg = val;
 }