target/riscv/pmp.c: respect mseccfg.RLB for pmpaddrX changes

When the rule-lock bypass (RLB) bit is set in the mseccfg CSR, the PMP
configuration lock bits must not apply. While this behavior is
implemented for the pmpcfgX CSRs, this bit is not respected for
changes to the pmpaddrX CSRs. This patch ensures that pmpaddrX CSR
writes work even on locked regions when the global rule-lock bypass is
enabled.

Signed-off-by: Leon Schuermann <leons@opentitan.org>
Reviewed-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20230829215046.1430463-1-leon@is.currently.online>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/pmp.c

@@ -44,6 +44,10 @@ static inline uint8_t pmp_get_a_field(uint8_t cfg)
  */
 static inline int pmp_is_locked(CPURISCVState *env, uint32_t pmp_index)
 {
+    /* mseccfg.RLB is set */
+    if (MSECCFG_RLB_ISSET(env)) {
+        return 0;
+    }
 
     if (env->pmp_state.pmp[pmp_index].cfg_reg & PMP_LOCK) {
         return 1;