[PATCH] target/riscv: pmp: Clear pmp/smepmp bits on reset

[Mayuresh Chitale]

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.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
---
 target/riscv/cpu.c | 11 +++++++++++
 target/riscv/pmp.c | 10 ++++++++++
 target/riscv/pmp.h |  1 +
 3 files changed, 22 insertions(+)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 0843461660..77ed653b8d 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -896,6 +896,17 @@ 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);
diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index 3f6c8cf08d..f3eb6e6585 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -131,6 +131,16 @@ 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;
+    }
+}
+
 static void pmp_decode_napot(target_ulong a, target_ulong *sa,
                              target_ulong *ea)
 {
diff --git a/target/riscv/pmp.h b/target/riscv/pmp.h
index cf5c99f8e6..2c5ec3cdf1 100644
--- a/target/riscv/pmp.h
+++ b/target/riscv/pmp.h
@@ -81,6 +81,7 @@ 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)
-- 
2.34.1