On Mon, Nov 27, 2023 at 11:37 AM Conor Dooley <conor.dooley@xxxxxxxxxxxxx> wrote: > > Hi, > > On Fri, Nov 24, 2023 at 08:21:37AM +0100, Christoph Muellner wrote: > > 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): > > I know this is an RFC, but it could probably do with a bit more compile > testing, as: > > > RISC-V: Add basic Ssdtso support > > This patch doesn't build for rv64 allmodconfig > > > RISC-V: Expose Ssdtso via hwprobe API > > This one seems to build fine > > > 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 > > These don't build for: > rv32 defconfig > rv64 allmodconfig > rv64 nommu Thanks for reporting this. You are absolutely right. In my defense, this patchset was compile-tested and got some limited run-time testing in QEMU. But after that, I wrote the documentation, which triggered a renaming of several function/macro names, and these changes did not see adequate testing. I am sorry for that. I've already fixed the patches (addressing the issues you have reported, plus other small issues). To not distract the ongoing discussion, I will not send an updated patchset right now. In case you are interested, you can find the latest changes (rebased on upstream/master) here: https://github.com/cmuellner/linux/tree/ssdtso I've also extended my local compile-test script to include all mentioned configs. In case you want to play a bit with these changes, you can also have a look at the QEMU patchset, which also got support for the prctl (which is not part of the published mailpatch): https://github.com/cmuellner/qemu/tree/ssdtso With these changes, you can run the kernel self-test binary in user-mode emulation. BR Christoph
