<!-- This is the upstream QEMU issue tracker. If you are able to, it will greatly facilitate bug triage if you attempt to reproduce the problem with the latest qemu.git master built from source. See https://www.qemu.org/download/#source for instructions on how to do this. QEMU generally supports the last two releases advertised on https://www.qemu.org/. Problems with distro-packaged versions of QEMU older than this should be reported to the distribution instead. See https://www.qemu.org/contribute/report-a-bug/ for additional guidance. If this is a security issue, please consult https://www.qemu.org/contribute/security-process/ --> ## Host environment - Operating system: Ubuntu 22.04.3 - OS/kernel version: 6.8.0-40-generic - Architecture: x86 - QEMU flavor: qemu-system-riscv32 - QEMU version: 9.1.1 ## Emulated/Virtualized environment - Operating system: Bare Metal - OS/kernel version: Bare Metal - Architecture: riscv32 ## Description of problem In a bare metal application, running on an emulated Opentitan board, if you set a timer interrupt threshold by writing to `rv_timer.COMPARE_UPPER0` and `rv_timer.COMPARE_LOWER0` before writing to `rv_timer.CTRL` to start the timer, then the interrupt does not fire. If you write to the `COMPARE_*` registers *after* starting the timer by writing to `CTRL`, then the interrupt fires correctly. I think the explanation is that [ibex_timer_update_irqs](https://gitlab.com/qemu-project/qemu/-/blob/master/hw/timer/ibex_timer.c?ref_type=heads#L61) has an early return if `rv_timer.CTRL` is not set. As a result, although writes to `COMPARE_*` always call `ibex_timer_update_irqs`, they don't have their intended side-effects before `CTRL` is unset. ## Steps to reproduce Write to `rv_timer.COMPARE_UPPER0` and `rv_timer.COMPARE_LOWER0` before you have set `rv_timer.CTRL`. Observe that no timer interrupt occurs. <!-- The line below ensures that proper tags are added to the issue. Please do not remove it. -->