On Arm a couple of only-on-hardware pitfalls are (a) cache maintenance -- QEMU doesn't model caches so won't notice if you forget to clean the dcache and flush

On Arm a couple of only-on-hardware pitfalls are (a) cache maintenance -- QEMU doesn't model caches so won't notice if you forget to clean the dcache and flush the icache before executing code you just wrote or modified and (b) synchronization/barriers -- QEMU doesn't reorder memory accesses and generally makes writes to system registers take effect immediately, so won't notice if you forget necessary barrier insns.