This patch adds a new instruction `mnret`. `mnret` is an M-mode-only
instruction that uses the values in `mnepc` and `mnstatus` to return to the
program counter, privilege mode, and virtualization mode of the
interrupted context.
Signed-off-by: Frank Chang <frank.ch...@sifive.com>
Signed-off-by: Tommy Wu <tommy...@sifive.com>
---
target/riscv/helper.h | 1 +
target/riscv/insn32.decode | 3 ++
.../riscv/insn_trans/trans_privileged.c.inc | 12 +++++
target/riscv/op_helper.c | 46 +++++++++++++++++++
4 files changed, 62 insertions(+)
diff --git a/target/riscv/helper.h b/target/riscv/helper.h
index 451261ce5a..16ea240d26 100644
--- a/target/riscv/helper.h
+++ b/target/riscv/helper.h
@@ -131,6 +131,7 @@ DEF_HELPER_6(csrrw_i128, tl, env, int, tl, tl, tl, tl)
#ifndef CONFIG_USER_ONLY
DEF_HELPER_1(sret, tl, env)
DEF_HELPER_1(mret, tl, env)
+DEF_HELPER_1(mnret, tl, env)
DEF_HELPER_1(wfi, void, env)
DEF_HELPER_1(wrs_nto, void, env)
DEF_HELPER_1(tlb_flush, void, env)
diff --git a/target/riscv/insn32.decode b/target/riscv/insn32.decode
index c45b8fa1d8..d320631e8c 100644
--- a/target/riscv/insn32.decode
+++ b/target/riscv/insn32.decode
@@ -121,6 +121,9 @@ wfi 0001000 00101 00000 000 00000 1110011
sfence_vma 0001001 ..... ..... 000 00000 1110011 @sfence_vma
sfence_vm 0001000 00100 ..... 000 00000 1110011 @sfence_vm
+# *** NMI ***
+mnret 0111000 00010 00000 000 00000 1110011
+
# *** RV32I Base Instruction Set ***
lui .................... ..... 0110111 @u
auipc .................... ..... 0010111 @u
diff --git a/target/riscv/insn_trans/trans_privileged.c.inc
b/target/riscv/insn_trans/trans_privileged.c.inc
index bc5263a4e0..06bc20dda4 100644
--- a/target/riscv/insn_trans/trans_privileged.c.inc
+++ b/target/riscv/insn_trans/trans_privileged.c.inc
@@ -106,6 +106,18 @@ static bool trans_mret(DisasContext *ctx, arg_mret *a)
#endif
}
+static bool trans_mnret(DisasContext *ctx, arg_mnret *a)
+{
+#ifndef CONFIG_USER_ONLY
+ gen_helper_mnret(cpu_pc, tcg_env);
+ tcg_gen_exit_tb(NULL, 0); /* no chaining */
+ ctx->base.is_jmp = DISAS_NORETURN;
+ return true;
+#else
+ return false;
+#endif
+}
+
static bool trans_wfi(DisasContext *ctx, arg_wfi *a)
{
#ifndef CONFIG_USER_ONLY
diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 25a5263573..3e26392e65 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -353,6 +353,52 @@ target_ulong helper_mret(CPURISCVState *env)
return retpc;
}
+target_ulong helper_mnret(CPURISCVState *env)
+{
+ if (!riscv_cpu_cfg(env)->ext_smrnmi) {
+ /* RNMI feature is not presented. */
+ riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
+ }
+
+ if (!(env->priv >= PRV_M)) {
+ riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
+ }
+
+ /* Get return PC from mnepc CSR. */
+ target_ulong retpc = env->mnepc;
+ if (!riscv_has_ext(env, RVC) && (retpc & 0x3)) {
+ riscv_raise_exception(env, RISCV_EXCP_INST_ADDR_MIS, GETPC());
+ }
+
+ /* Get previous privilege level from mnstatus CSR. */
+ target_ulong prev_priv = get_field(env->mnstatus, MNSTATUS_MNPP);
+
+ if (riscv_cpu_cfg(env)->pmp &&
+ !pmp_get_num_rules(env) && (prev_priv != PRV_M)) {
+ riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
+ }
+
+ target_ulong prev_virt = get_field(env->mnstatus, MNSTATUS_MNPV) &&
+ (prev_priv != PRV_M);
+ env->mnstatus = set_field(env->mnstatus, MNSTATUS_NMIE, true);
+
+ /*
+ * If MNRET changes the privilege mode to a mode
+ * less privileged than M, it also sets mstatus.MPRV to 0.
+ */
+ if (prev_priv < PRV_M) {
+ env->mstatus = set_field(env->mstatus, MSTATUS_MPRV, false);
+ }
+
+ if (riscv_has_ext(env, RVH) && prev_virt) {
+ riscv_cpu_swap_hypervisor_regs(env);
+ }
+
+ riscv_cpu_set_mode(env, prev_priv, prev_virt);
+
+ return retpc;
+}
+
void helper_wfi(CPURISCVState *env)
{
CPUState *cs = env_cpu(env);
--
2.39.3
