[PATCH] target/riscv/tcg: sret in virtual user mode raises virtual instruction exception

Currently, when a `sret` is executed in virtual user mode, qemu
raise an `illegal instruction exception`, but in this case the correct
behavior is to raise a `virtual instruction exception` and the code
already contains a check to it, but it's not enough to catch. This
patch is useful to improve the correctness of the virtualization of
the risc v architecture.

Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3622

Signed-off-by: Christian S. Lima <[email protected]>
---
 target/riscv/tcg/op_helper.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/target/riscv/tcg/op_helper.c b/target/riscv/tcg/op_helper.c
index ba3c7da375..429a6186a7 100644
--- a/target/riscv/tcg/op_helper.c
+++ b/target/riscv/tcg/op_helper.c
@@ -293,6 +293,10 @@ target_ulong helper_sret(CPURISCVState *env)
     const privilege_mode_t src_priv = env->priv;
     const bool src_virt = env->virt_enabled;
 
+    if ((env->virt_enabled && env->priv < PRV_S) || (env->virt_enabled && get_field(env->hstatus, HSTATUS_VTSR))) {
+        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, GETPC());
+    }
+
     if (!(env->priv >= PRV_S)) {
         riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
     }
@@ -308,10 +312,6 @@ target_ulong helper_sret(CPURISCVState *env)
         riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
     }
 
-    if (env->virt_enabled && get_field(env->hstatus, HSTATUS_VTSR)) {
-        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, GETPC());
-    }
-
     mstatus = env->mstatus;
     prev_priv = get_field(mstatus, MSTATUS_SPP);
     mstatus = set_field(mstatus, MSTATUS_SIE,
-- 
2.53.0