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While the up-to-date data may reside in any agent of Ruby's memory hierarchy, there's an optional backing store in Ruby that provides a 'correct' view of the physical memory. When it is enabled by the user, every Ruby memory access will update this global memory view as well upon finishing. The issue is that Ruby's atomic access, used in fast-forward, does not currently access the backing store, leading to data incorrectness. More specifically, at the very beginning stage of the simulation, a loader loads the program into the backing store using functional accesses. Then the program starts execution with fast-forward enabled, using atomic accesses for faster simulation. But because atomic access only accesses the real memory hierarchy, the CPU fetches incorrect instructions. The fix is simple. Just make Ruby's atomic access update the backing store as well as the real physical memory. Change-Id: I2541d923e18ea488d383097ca7abd4124e47e59b Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26343 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Onur Kayıran <onur.kayiran@amd.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com>
This is the gem5 simulator. The main website can be found at http://www.gem5.org A good starting point is http://www.gem5.org/about, and for more information about building the simulator and getting started please see http://www.gem5.org/documentation and http://www.gem5.org/documentation/learning_gem5/introduction. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, SWIG, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/documentation/general_docs/building for more details concerning the minimum versions of the aforementioned tools. Once you have all dependencies resolved, type 'scons build/<ARCH>/gem5.opt' where ARCH is one of ARM, NULL, MIPS, POWER, SPARC, or X86. This will build an optimized version of the gem5 binary (gem5.opt) for the the specified architecture. See http://www.gem5.org/documentation/general_docs/building for more details and options. The basic source release includes these subdirectories: - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - src: source code of the gem5 simulator - system: source for some optional system software for simulated systems - tests: regression tests - util: useful utility programs and files To run full-system simulations, you will need compiled system firmware (console and PALcode for Alpha), kernel binaries and one or more disk images. If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.