By Jakob Engblom
The other day, I spent some time getting a new operating system up on one of our Simics virtual platforms. The platform is stable, the hardware is shipping and it is being used with the very software I was setting up. However, as the operating system was booting, I got quite a lot of warnings from Simics about incorrect hardware settings. The operating system still worked, however, so why did we see all these warnings? Actually, when is it prudent to issue warnings to a user about suspicious uses of hardware? When building Simics models, we want them to be helpful and offer warnings as much as possible – especially for cases where some uses might be considered technically "correct" but are actually somewhat suspicious.
A virtual platform like Simics can print warnings to the simulation console when software performs operations that are not legal according to the hardware specification. Typical examples are writing to offsets in device register banks where there are no registers, changing the value of bits which are marked as "reserved", or writing illegal values to configuration registers.