Yea, with speculative execution it's not impossible for the CPU to fetch from a bogus physical address in kernel mode due to a misspeculated path. Physical memory should respond to this with a Bad Address response, which then gets ignored when the misspeculated path is squashed.
Steve On Fri, May 29, 2009 at 4:51 PM, Rick Strong <[email protected]> wrote: > Hi all, > > For the O3 cpu running several of the parsec benchmarks, let's focus on > x264 with 16 cores. I see that it's fetch unit requests 0xffffffc0 which > fails in the physmem because it is not within the valid address range > for the functional memory. The address is the result of "iew: Execute: > Branch mispredict" being detected and execute redirects fetch to PC: > 0xffffffc0. This strange behavior does not occur when I use > SimpleTimingCPU. Is there any potential for the iew stage to redirect > fetch to a bogus address, that is inst->readNextPC() in iew_impl.hh > returns a bogus address that would propagate to the memory system and be > caught later? > > Thanks in advance, > -Rick > > > > _______________________________________________ > m5-users mailing list > [email protected] > http://m5sim.org/cgi-bin/mailman/listinfo/m5-users >
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