[PATCH 11/13] target/riscv: Switch context in exception return

[LIU Zhiwei]

After excpetion return, we should give a xlen view of context in new
priveledge, including the general registers, pc, and CSRs.

Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
---
 target/riscv/helper.h                         |  1 +
 .../riscv/insn_trans/trans_privileged.c.inc   |  2 ++
 target/riscv/op_helper.c                      | 26 +++++++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/target/riscv/helper.h b/target/riscv/helper.h
index e198d43981..9b379d7232 100644
--- a/target/riscv/helper.h
+++ b/target/riscv/helper.h
@@ -71,6 +71,7 @@ DEF_HELPER_2(sret, tl, env, tl)
 DEF_HELPER_2(mret, tl, env, tl)
 DEF_HELPER_1(wfi, void, env)
 DEF_HELPER_1(tlb_flush, void, env)
+DEF_HELPER_1(switch_context_xl, void, env)
 #endif
 
 /* Hypervisor functions */
diff --git a/target/riscv/insn_trans/trans_privileged.c.inc 
b/target/riscv/insn_trans/trans_privileged.c.inc
index 75c6ef80a6..6e39632f83 100644
--- a/target/riscv/insn_trans/trans_privileged.c.inc
+++ b/target/riscv/insn_trans/trans_privileged.c.inc
@@ -78,6 +78,7 @@ static bool trans_sret(DisasContext *ctx, arg_sret *a)
 
     if (has_ext(ctx, RVS)) {
         gen_helper_sret(cpu_pc, cpu_env, cpu_pc);
+        gen_helper_switch_context_xl(cpu_env);
         tcg_gen_exit_tb(NULL, 0); /* no chaining */
         ctx->base.is_jmp = DISAS_NORETURN;
     } else {
@@ -94,6 +95,7 @@ static bool trans_mret(DisasContext *ctx, arg_mret *a)
 #ifndef CONFIG_USER_ONLY
     tcg_gen_movi_tl(cpu_pc, ctx->base.pc_next);
     gen_helper_mret(cpu_pc, cpu_env, cpu_pc);
+    gen_helper_switch_context_xl(cpu_env);
     tcg_gen_exit_tb(NULL, 0); /* no chaining */
     ctx->base.is_jmp = DISAS_NORETURN;
     return true;
diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index ee7c24efe7..20cf8ad883 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -70,6 +70,32 @@ target_ulong helper_csrrw(CPURISCVState *env, int csr,
 }
 
 #ifndef CONFIG_USER_ONLY
+void helper_switch_context_xl(CPURISCVState *env)
+{
+    RISCVMXL xl = cpu_get_xl(env);
+    if (xl == env->misa_mxl_max) {
+        return;
+    }
+    assert(xl < env->misa_mxl_max);
+    switch (xl) {
+    case MXL_RV32:
+        for (int i = 1; i < 32; i++) {
+            env->gpr[i] = (int32_t)env->gpr[i];
+        }
+        env->pc = (int32_t)env->pc;
+        /*
+         * For the read-only bits of the previous-width CSR, the bits at the
+         * same positions in the temporary register are set to zeros.
+         */
+        if ((env->priv == PRV_U) && (env->misa_ext & RVV)) {
+            env->vl = 0;
+            env->vtype = 0;
+        }
+        break;
+    default:
+        break;
+    }
+}
 
 target_ulong helper_sret(CPURISCVState *env, target_ulong cpu_pc_deb)
 {
-- 
2.25.1