On Sun, May 12, 2024 at 09:10:49AM +0200, Stanisław Kardach wrote: > On Thu, May 2, 2024 at 4:44 PM Daniel Gregory > <daniel.greg...@bytedance.com> wrote: > > diff --git a/config/riscv/meson.build b/config/riscv/meson.build > > index 07d7d9da23..4cfdc42ecb 100644 > > --- a/config/riscv/meson.build > > +++ b/config/riscv/meson.build > > @@ -26,6 +26,11 @@ flags_common = [ > > # read from /proc/device-tree/cpus/timebase-frequency. This property is > > # guaranteed on Linux, as riscv time_init() requires it. > > ['RTE_RISCV_TIME_FREQ', 0], > > + > > + # Enable use of RISC-V Wait-on-Reservation-Set extension (Zawrs) > > + # Mitigates looping when polling on memory locations > > + # Make sure to add '_zawrs' to your target's -march below > > + ['RTE_RISCV_ZAWRS', false] > A bit orthogonal to this patch (or maybe not?) > Should we perhaps add a Qemu target in meson.build which would have > the modified -march for what qemu supports now?
Yes, I can see that being worth doing as part of this patch. In addition to Zawrs for this patch, GCC 13+ should generate prefetch instructions for __builtin_prefetch() (lib/eal/include/generic/rte_prefetch.h) if the Zicbop extension is enabled. Any more in particular you think would benefit or would it be best to add every extension GCC 14 supports? > Or perhaps add machine detection logic based either on the "riscv,isa" > cpu@0 property in the DT or RHCT ACPI table? I have had a look and, at least on QEMU 9, this seems non-trivial. The RHCT acpi table at /proc/cpuinfo doesn't list every extension present (eg. it's missing Zawrs), and the DT, whilst complete, can't be fed directly into GCC because QEMU reports several newer and non-ratified extensions that GCC doesn't support yet. > Or add perhaps some other way we could specify the extension list > suffix for -march? Setting -Dcpu_instruction_set to some arbitrary ISA could work with somes minor changes to the build script to not discard it in favour of rv64gc. Then, we could add a map from ISA extensions to flags that are enabled when that extension is present in cpu_instruction_set? Thanks for your review, Daniel
