[PATCH qemu v2] target/riscv: Check ext_zca for misaligned return address of mret/sret.

[~yuming]

From: Yu-Ming Chang <yumin...@andestech.com>

We only check RVC to allow 16-bit aligned return addreses. This will
cause issues when only ext_zca is enabled without RVC: 16-bit
instructions are allowed, but 16-bit aligned return address are not.
We should also check ext_zca to permit 16-bit aligned return addresses.

Signed-off-by: Yu-Ming Chang <yumin...@andestech.com>
---
The v2 has been updated to provide more explanation.

 target/riscv/op_helper.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index eddedacf4b..891002f954 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -269,8 +269,10 @@ target_ulong helper_sret(CPURISCVState *env)
     }
 
     target_ulong retpc = env->sepc;
-    if (!riscv_has_ext(env, RVC) && (retpc & 0x3)) {
-        riscv_raise_exception(env, RISCV_EXCP_INST_ADDR_MIS, GETPC());
+    if (!riscv_has_ext(env, RVC) && !env_archcpu(env)->cfg.ext_zca) {
+        if ((retpc & 0x3) != 0) {
+            riscv_raise_exception(env, RISCV_EXCP_INST_ADDR_MIS, GETPC());
+        }
     }
 
     if (get_field(env->mstatus, MSTATUS_TSR) && !(env->priv >= PRV_M)) {
@@ -328,8 +330,10 @@ target_ulong helper_mret(CPURISCVState *env)
     }
 
     target_ulong retpc = env->mepc;
-    if (!riscv_has_ext(env, RVC) && (retpc & 0x3)) {
-        riscv_raise_exception(env, RISCV_EXCP_INST_ADDR_MIS, GETPC());
+    if (!riscv_has_ext(env, RVC) && !env_archcpu(env)->cfg.ext_zca) {
+        if ((retpc & 0x3) != 0) {
+            riscv_raise_exception(env, RISCV_EXCP_INST_ADDR_MIS, GETPC());
+        }
     }
 
     uint64_t mstatus = env->mstatus;
-- 
2.45.3