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SMMU circular queues have a wrap bit which is used in order to distinguish between an empty queue and a full queue. According to SMMUv3 spec: Each index has a wrap flag, represented by the next higher bit adjacent to the index value contained in PROD and CONS. This bit must toggle each time the index wraps off the high end and back onto the low end of the buffer. It is the responsibility of the owner of each index, producer or consumer, to toggle this bit when the owner updates the index after wrapping. It is intended that software reads the register, increments or wraps the index (toggling wrap when required) and writes back both wrap and index fields at the same time. Change-Id: Idfeb397141f3627c2878caaeaa2625fadf671d2a Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Reviewed-by: Michiel Van Tol <michiel.vantol@arm.com> Reviewed-by: Adrian Herrera <adrian.herrera@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19311 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Ciro Santilli <ciro.santilli@arm.com> Maintainer: Andreas Sandberg <andreas.sandberg@arm.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/Introduction, and for more information about building the simulator and getting started please see http://www.gem5.org/Documentation and http://www.gem5.org/Tutorials. 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/Dependencies 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 ALPHA, 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/Build_System for more details and options. With the simulator built, have a look at http://www.gem5.org/Running_gem5 for more information on how to use gem5. 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. Please see the gem5 download page for these items at http://www.gem5.org/Download If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.