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When just forwarding a WU request, the controller waits until the WU is acked from downstream before sending the ack upstream. This prevents snoops clearing valid WU data. JIRA: https://gem5.atlassian.net/browse/GEM5-1195 This was more likely to happen with shared exclusive caches, e.g: assume core C1 and C2 with private L1/L2 and a shared exclusive L3. C1 has as dirty copy of the line while C2 issues a WriteUnique request to that line. The line state is RU in the L3, so the L3 will just forward the request to the HNF, so: - C2 issues WU to L3 cache - L3 acks the WU, allowing C2 to send the data, while concurrently forwarding the WU to the HNF. - L3 receives data from C2 - HNF sends invalidating snoops upstream because line is RU - The snoop hazards with the pending WU at the L3 and invalidates the data previously received. This causes an assertion to fail when we resume handling the WU. Change-Id: I51e457e0bdb648c0fff3f702b7d2c95dcf431dc5 Signed-off-by: Tiago Mück <tiago.muck@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/59990 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Maintainer: Jason Lowe-Power <power.jg@gmail.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, 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 these tools. Once you have all dependencies resolved, type 'scons build/<CONFIG>/gem5.opt' where CONFIG is one of the options in build_opts like ARM, NULL, MIPS, POWER, SPARC, X86, Garnet_standalone, etc. This will build an optimized version of the gem5 binary (gem5.opt) with the the specified configuration. See http://www.gem5.org/documentation/general_docs/building for more details and options. The main source tree includes these subdirectories: - build_opts: pre-made default configurations for gem5 - build_tools: tools used internally by gem5's build process. - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - include: include files for use in other programs - site_scons: modular components of the build system - 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 may need compiled system firmware, kernel binaries and one or more disk images, depending on gem5's configuration and what type of workload you're trying to run. Many of those resources can be downloaded from http://resources.gem5.org, and/or from the git repository here: https://gem5.googlesource.com/public/gem5-resources/ If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.