[Gems-users] Regarding Supervier Mode bit in Simics 3 and gems 2.1

[sjafri@xxxxxxxxxx]

Hi,

I am seeing some very strange behaviour while using gems-2.1 with Simics 3.0.31. 

It seems that the first couple of thousands of memory references belonging to
the benchmark are delivered to ruby with the supervisor bit on. Thus if I have a
toy benchmark which uses Xactions, my reported read and write sets are zero. 


I placed my check in ruby/module/ruby.c where the mem_trans structure is
received from Simics. I further added code that would simply crash ruby if the
supervisor bit is set to 0. Then I ran the toy benchmark. It completed execution
without any incident. Checking cpu mode counters in simics showed that simics
had indeed executed some user mode instructions but none of them made it to
ruby. I then repeated the test with another much longer running benchmark. This
showed that ruby received a user mode memory reference after simics had
reportedly executed almost 2000 user mode references.

Can any one confirm or reject my suspicions that simics is simply giving the
incorrect user mode bit?



Ali Raza