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This patch is adding the MISCREG_UNSERIALIZE flag to expose the user to the following checkpoint compatibility problem: What happens when a checkpoint is restored with a different architectural configuration? The current behaviour is to silently restore the checkpoint and to populate the ISA registers accordingly. However some of these restored values will be used and some of them will be actually discarded. For example the value of the MISCREG_ID_AA64ISAR0_EL1 register (initially configured at construction time [1]) will be overwritten by the checkpointed value in ISA::unserialize (checkpointed params win over current params). On the other hand we "discard" the checkpointed value for registers handled in the ISA::readMiscReg method (not accessing the storage) like MISCREG_ID_AA64PFR0_EL1 [2] (current params win over checkpointed params). In other words some registers will be unserialized while some others will discard the checkpointed value in favour of the current configuration setup. This categorization is currently implicit and it ultimately depends on whether or not a register read access its storage (see MISCREG_ID_AA64PFR0_EL1 above). With this patch we formalize this distinction. We allow the developer to be explict on which register should not be unserialized and should instead use the new simulation parameters. If there is a mismatch between the reset value of such register and the checkpointed one, we warn the user and we undo the unserialization for such register. [1]: https://github.com/gem5/gem5/blob/v22.1.0.0/src/arch/arm/isa.cc#L437 [2]: https://github.com/gem5/gem5/blob/v22.1.0.0/src/arch/arm/isa.cc#L1019 Change-Id: Icea6563ee5816b14a097926b5734f2fce10530c7 Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Reviewed-by: Richard Cooper <richard.cooper@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/70557 Maintainer: Jason Lowe-Power <power.jg@gmail.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, 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.