[PATCH] target/riscv: Fix mret exception cause when no pmp rule is configured

[Bin Meng]

The priv spec v1.12 says:

  If no PMP entry matches an M-mode access, the access succeeds. If
  no PMP entry matches an S-mode or U-mode access, but at least one
  PMP entry is implemented, the access fails. Failed accesses generate
  an instruction, load, or store access-fault exception.

At present the exception cause is set to 'illegal instruction' but
should have been 'instruction access fault'.

Fixes: d102f19a2085 ("target/riscv/pmp: Raise exception if no PMP entry is 
configured")
Signed-off-by: Bin Meng <bmeng@tinylab.org>
---

 target/riscv/op_helper.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 09f1f5185d..d7af7f056b 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -202,7 +202,7 @@ target_ulong helper_mret(CPURISCVState *env)
 
     if (riscv_feature(env, RISCV_FEATURE_PMP) &&
         !pmp_get_num_rules(env) && (prev_priv != PRV_M)) {
-        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
+        riscv_raise_exception(env, RISCV_EXCP_INST_ACCESS_FAULT, GETPC());
     }
 
     target_ulong prev_virt = get_field(env->mstatus, MSTATUS_MPV);
-- 
2.34.1