target/riscv: pmp: Clear pmp/smepmp bits on reset

As per the Priv and Smepmp specifications, certain bits such as the 'L'
bit of pmp entries and mseccfg.MML can only be cleared upon reset and it
is necessary to do so to allow 'M' mode firmware to correctly reinitialize
the pmp/smpemp state across reboots. As required by the spec, also clear
the 'A' field of pmp entries.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231019065644.1431798-1-mchitale@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -884,6 +884,17 @@ static void riscv_cpu_reset_hold(Object *obj)
     }
     /* mmte is supposed to have pm.current hardwired to 1 */
     env->mmte |= (EXT_STATUS_INITIAL | MMTE_M_PM_CURRENT);
+
+    /*
+     * Clear mseccfg and unlock all the PMP entries upon reset.
+     * This is allowed as per the priv and smepmp specifications
+     * and is needed to clear stale entries across reboots.
+     */
+    if (riscv_cpu_cfg(env)->ext_smepmp) {
+        env->mseccfg = 0;
+    }
+
+    pmp_unlock_entries(env);
 #endif
     env->xl = riscv_cpu_mxl(env);
     riscv_cpu_update_mask(env);

target/riscv/pmp.c

@@ -135,6 +135,16 @@ static bool pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
     return false;
 }
 
+void pmp_unlock_entries(CPURISCVState *env)
+{
+    uint32_t pmp_num = pmp_get_num_rules(env);
+    int i;
+
+    for (i = 0; i < pmp_num; i++) {
+        env->pmp_state.pmp[i].cfg_reg &= ~(PMP_LOCK | PMP_AMATCH);
+    }
+}
+
 static void pmp_decode_napot(target_ulong a, target_ulong *sa,
                              target_ulong *ea)
 {

target/riscv/pmp.h

@@ -28,6 +28,7 @@ typedef enum {
     PMP_READ  = 1 << 0,
     PMP_WRITE = 1 << 1,
     PMP_EXEC  = 1 << 2,
+    PMP_AMATCH = (3 << 3),
     PMP_LOCK  = 1 << 7
 } pmp_priv_t;
 
@@ -81,6 +82,7 @@ void pmp_update_rule_addr(CPURISCVState *env, uint32_t pmp_index);
 void pmp_update_rule_nums(CPURISCVState *env);
 uint32_t pmp_get_num_rules(CPURISCVState *env);
 int pmp_priv_to_page_prot(pmp_priv_t pmp_priv);
+void pmp_unlock_entries(CPURISCVState *env);
 
 #define MSECCFG_MML_ISSET(env) get_field(env->mseccfg, MSECCFG_MML)
 #define MSECCFG_MMWP_ISSET(env) get_field(env->mseccfg, MSECCFG_MMWP)