[PATCH] target/riscv: Disallow WFI instruction from U-mode

[Jonathan Behrens]

>From the RISC-V Priviliged Specification:

"When S-mode is implemented, then executing WFI in U-mode causes an illegal
instruction exception, unless it completes within an implementation-specific,
bounded time limit. A future revision of this specification might add a feature
that allows S-mode to selectively permit WFI in U-mode."

Signed-off-by: Jonathan Behrens <address@hidden>
Reviewed-by: Alistair Francis <address@hidden>
---
 target/riscv/op_helper.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 331cc36232..2e5a980192 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -129,10 +129,10 @@ target_ulong helper_mret(CPURISCVState *env, target_ulong 
cpu_pc_deb)
 void helper_wfi(CPURISCVState *env)
 {
     CPUState *cs = env_cpu(env);
-
-    if (env->priv == PRV_S &&
-        env->priv_ver >= PRIV_VERSION_1_10_0 &&
-        get_field(env->mstatus, MSTATUS_TW)) {
+    if (!(env->priv >= PRV_S) ||
+        (env->priv == PRV_S &&
+         env->priv_ver >= PRIV_VERSION_1_10_0 &&
+         get_field(env->mstatus, MSTATUS_TW))) {
         riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
     } else {
         cs->halted = 1;
-- 
2.25.0