[verilator] uart_smoketest_sim_verilator times out immediately after simctrl.Exec()

Description

Description

I am trying to run the UART smoketest using the Verilator backend.

The Verilator simulation model (//hw:verilator_real) builds successfully using Bazel. However, when running the UART smoketest target (//sw/device/tests:uart_smoketest_sim_verilator), the simulation consistently times out immediately after simctrl.Exec() is called.
I am not sure whether the issue is related to the OpenTitan simulation flow, the Verilator backend integration, or my local setup, and would appreciate any guidance.

Environment

• Branch: master
• OS: Ubuntu 26.04 LTS running under WSL2 (Windows 11)
• Verilator: 5.049
• Python (OpenTitan): 3.10.16
• Edalize: 0.6.3

Commands

Build

./bazelisk.sh build //hw:verilator_real

Build completes successfully and generates the Verilator simulation model.

Run

./bazelisk.sh test --test_output=all //sw/device/tests:uart_smoketest_sim_verilator

Observed Output

Simulation of OpenTitan Earl Grey

[TB] About to call simctrl.Exec()

Tracing can be toggled by sending SIGUSR1 to this process:
$ kill -USR1

Error: Timed out

The simulator launches successfully, but the software testcase never appears to start executing. I also added debug messages in test_main(), but they are never printed.

Expected Behavior

The UART smoketest should execute successfully and complete with a PASS status

Start by reproducing //sw/device/tests:uart_smoketest_sim_verilator after building //hw:verilator_real, and trace the flow around simctrl.Exec(). Check why the simulator does not reach the UART smoketest's test_main(); done means the test executes and completes with PASS instead of timing out.