Welcome to our first “official” gem5 release! gem5 v188.8.131.52 was a “test” release, but this one has release notes, so it must be official!
Thank you to everyone that made this release possible! This has been a very productive release with over 70 issues closed, over 500 commits, and 31 unique contributors. Below are some of the highlights, though I‘m sure I’ve missed some important changes.
- gem5-resources repository
- This new repository will store all of the sources (e.g., code) used to create testing and research resources. This includes disk images, testing binaries, kernel binaries, etc.
- Binaries created with the sources are hosted on dist.gem5.org.
- Details on the new page for resources: http://www.gem5.org/documentation/general_docs/gem5_resources.
- Memory SimObjects can now be initialized using an image file using the image_file parameter.
- [USER-FACING CHANGE] The m5 utility has been revamped with a new build system based on scons, tests, and updated and more consistent feature support.
- To build, now use
scons build/<arch>/out/m5, not
- Documentation coming soon.
- Robust support for marshalling data from a function call inside the simulation to a function within gem5 using a predefined set of rules.
- Developers can specify an ABI for guest<->simulator calls and then “just call functions”.
- Unifies pseudo-inst, syscall, and other support.
- Code within gem5 has been updated. However, users which added new pseudo-ops may have to update their code.
- [PYTHON API CHANGE] Workload configuration pulled out into its own object, simplifying the System object and making workload configuration more modular and flexible.
- Sv39 paging has been added to the RISC-V ISA, bringing gem5 close to running Linux on RISC-V.
- (Some) Baremetal OSes are now supported.
- Improvements to DRAM model:
- Added support for verifying available command bandwidth.
- Added support for multi-cycle commands.
- Added new timing parameters.
- Added ability to interleave bursts.
- Added LPDDR5 configurations.
- [Developer change] We are beginning to document gem5 APIs.
- Currently, only SimObjects and the APIs they depend on have been documented.
- We are using doxygen to mark “stable APIs” and will use manual code review to make sure the APIs stay stable.
- More information will be coming during gem5-20.1 development.
- Support for the ALPHA ISA has been dropped.
- All ALPHA ISA code has been removed
- Old “rcS” scripts for ALPHA have been removed
New supported platforms
- Compiling and running gem5 with Python 3 is now fully supported.
- Lots of code changes required for this.
- There may still be some python code that‘s not up to date. Please open a Jira ticket if you find any code that doesn’t work with python3.
- gem5 now supports Ubuntu 20.04.
- Compiling gem5 with GCC 8 and 9 is now supported.
- Compiling with clang up to version 9 is now supported.
- Scons-based tests have been migrated to the testlib framework.
- Tests can now be run with
tests/main.py, except for the unittests.
- Please consult TESTING.md for more information on how these may be run.
- We are continuing to work on CI tests. Most of the plumbing is there for Google Cloud Build integration. See the Jira issue for details.
Other API changes
- [API CHANGE] Ruby's prefetcher renamed to RubyPrefetcher.
- Any SLICC protocols with prefetchers need to be updated.
- Some config scripts for Ruby protocols with prefetchers may need to be updated.
- [API CHANGE] SE mode improvements.
- Better support for the mmap and related syscalls.
- A new virtual memory area API for tracking SE mode allocations.
- When implementing syscalls, the way that guest memory is allocated changes. All code in gem5 is updated, but if there are any external syscalls, they may need be updated.
- [COMMAND LINE CHANGE] The
--disk-image argument to
fs.py is now optional.
- However, the disk image names are no longer implied.
- The script still implicitly searches
M5_PATH, but the name of the disk image must be specified.
- [API CHANGE] SLICC
queueMemory is now
- All protocol configs must be updated with another message buffer in the memory controllers (directories).
- All protocol SLICC files must replace
enqueue to another “special” message buffer named
- This allows finite buffering between the cache controllers and DRAMCtrl.
- [API CHANGE] Added Prefetcher namespace
- All prefetchers' names have changed from
- If you have any prefetchers that are not in the gem5 mainline, your code will likely need to be updated.
- Implemented ARMv8.3-CompNum, SIMD complex number extension.
- Support for Arm Trusted Firmware + u-boot with the new VExpress_GEM5_Foundation platform
- Removed author list from source files.
- This was originally so future people would know who to contact.
- However, it was difficult to maintain and quickly out of date.
- Copyright is unchanged.
- Improvements to gem5's power model.
- MESI_Three_Level Ruby protocol bugfixes.
- Ruby functional reads now work in more cases.
- Indirect branch stats work correctly now.