5d0a7b6a6c
Per RISC-V ISA Manual, vol II, section 3.1.6.6, page 26, the SD bit is
a read-only bit indicating whether any of FS, VS, and XS fields being
in the respective dirty state.
Per section 3.1.6, page 20, the SD bit is the most significant bit of
the mstatus register for both RV32 and RV64.
Per section 3.1.6.6, page 29, the explicit formula for updating the SD is,
SD = ((FS==DIRTY) | (XS==DIRTY) | (VS==DIRTY))
Previously in gem5, this bit is not updated anywhere in the gem5
implementation. This cause an issue of incorrectly saving the context
before entering the system call and consequently, incorecttly restoring
the context after a system call as described here [1].
Ideally, we want to update the SD after every relevant instruction;
however, lazily updating the Status register upon its read produces
the same effect.
[1] https://gem5-review.googlesource.com/c/public/gem5/+/65272/
Change-Id: I1db0cc619d43bc5bacb1d03f6f214345d9d90e28
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/65273
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: 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.