From: Christoph Müllner <christoph.muellner@xxxxxxxx> The upcoming RISC-V Ssdtso specification introduces a bit in the senvcfg CSR to switch the memory consistency model at run-time from RVWMO to TSO (and back). The active consistency model can therefore be switched on a per-hart base and managed by the kernel on a per-process/thread base. This patch implements basic Ssdtso support and adds a prctl API on top so that user-space processes can switch to a stronger memory consistency model (than the kernel was written for) at run-time. I am not sure if other architectures support switching the memory consistency model at run-time, but designing the prctl API in an arch-independent way allows reusing it in the future. The patchset also comes with a short documentation of the prctl API. This series is based on the second draft of the Ssdtso specification which was published recently on an RVI list: https://lists.riscv.org/g/tech-arch-review/message/183 Note, that the Ssdtso specification is in development state (i.e., not frozen or even ratified) which is also the reason why I marked the series as RFC. One aspect that is not covered in this patchset is virtualization. It is planned to add virtualization support in a later version. Hints/suggestions on how to implement this part are very much appreciated. Christoph Müllner (5): RISC-V: Add basic Ssdtso support RISC-V: Expose Ssdtso via hwprobe API uapi: prctl: Add new prctl call to set/get the memory consistency model RISC-V: Implement prctl call to set/get the memory consistency model RISC-V: selftests: Add DTSO tests Documentation/arch/riscv/hwprobe.rst | 3 + .../mm/dynamic-memory-consistency-model.rst | 76 ++++++++++++++++++ arch/riscv/Kconfig | 10 +++ arch/riscv/include/asm/csr.h | 1 + arch/riscv/include/asm/dtso.h | 74 ++++++++++++++++++ arch/riscv/include/asm/hwcap.h | 1 + arch/riscv/include/asm/processor.h | 8 ++ arch/riscv/include/asm/switch_to.h | 3 + arch/riscv/include/uapi/asm/hwprobe.h | 1 + arch/riscv/kernel/Makefile | 1 + arch/riscv/kernel/cpufeature.c | 1 + arch/riscv/kernel/dtso.c | 33 ++++++++ arch/riscv/kernel/process.c | 4 + arch/riscv/kernel/sys_riscv.c | 1 + include/uapi/linux/prctl.h | 5 ++ kernel/sys.c | 12 +++ tools/testing/selftests/riscv/Makefile | 2 +- tools/testing/selftests/riscv/dtso/.gitignore | 1 + tools/testing/selftests/riscv/dtso/Makefile | 11 +++ tools/testing/selftests/riscv/dtso/dtso.c | 77 +++++++++++++++++++ 20 files changed, 324 insertions(+), 1 deletion(-) create mode 100644 Documentation/mm/dynamic-memory-consistency-model.rst create mode 100644 arch/riscv/include/asm/dtso.h create mode 100644 arch/riscv/kernel/dtso.c create mode 100644 tools/testing/selftests/riscv/dtso/.gitignore create mode 100644 tools/testing/selftests/riscv/dtso/Makefile create mode 100644 tools/testing/selftests/riscv/dtso/dtso.c -- 2.41.0
