Okay, so I'm trying to figure out whether this bug report about QEMU should be classified as 'user-mode' or 'system-mode'. Let me read through the problem description again carefully. The issue is that when a guest (which would be running in user mode) tries to write to ROM memory, which is supposed to be read-only, QEMU currently ignores the write silently. The suggestion is that instead, it should call cpu_transaction_failed, similar to how MMIO operations fail. This function, do_transaction_failed, is meant for handling failed memory transactions like bus faults or external aborts. Looking at what different CPUs do when this happens: they raise various exceptions like data aborts, bus errors, etc. These are all system-level exceptions because they're related to hardware-level issues that the CPU would encounter, not user-level application errors. For example, an ARM CPU raising a data abort exception is definitely a system-mode issue. ROM memory being accessed is part of the system's physical memory map, so writing to it without proper permissions should trigger a system-level fault rather than something a user-mode application would handle. The cpu_transaction_failed callback seems to be intended for such low-level hardware issues, not for user-space errors. Therefore, this bug report is related to how QEMU handles system-level transactions and exceptions when memory access violations occur in the guest environment. It's about ensuring that such accesses are properly handled at the system level, potentially affecting the operation of device drivers or the operating system running in the VM, rather than user applications. system