Messages in this thread | | | Date | Thu, 18 Apr 2024 21:10:54 +0200 | From | Andrew Jones <> | Subject | Re: [RFC 1/2] riscv: process: Introduce idle thread using Zawrs extension |
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On Thu, Apr 18, 2024 at 04:05:55PM +0100, Conor Dooley wrote: > + Drew, > > On Thu, Apr 18, 2024 at 07:49:41PM +0800, Xu Lu wrote: > > The Zawrs extension introduces a new instruction WRS.NTO, which will > > register a reservation set and causes the hart to temporarily stall > > execution in a low-power state until a store occurs to the reservation > > set or an interrupt is observed. > > > > This commit implements new version of idle thread for RISC-V via Zawrs > > extension. > > > > Signed-off-by: Xu Lu <luxu.kernel@bytedance.com> > > Reviewed-by: Hangjing Li <lihangjing@bytedance.com> > > Reviewed-by: Liang Deng <dengliang.1214@bytedance.com> > > Reviewed-by: Wen Chai <chaiwen.cc@bytedance.com> > > --- > > arch/riscv/Kconfig | 24 +++++++++++++++++ > > arch/riscv/include/asm/cpuidle.h | 11 +------- > > arch/riscv/include/asm/hwcap.h | 1 + > > arch/riscv/include/asm/processor.h | 17 +++++++++++++ > > arch/riscv/kernel/cpu.c | 5 ++++ > > arch/riscv/kernel/cpufeature.c | 1 + > > arch/riscv/kernel/process.c | 41 +++++++++++++++++++++++++++++- > > 7 files changed, 89 insertions(+), 11 deletions(-) > > > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > > index be09c8836d56..a0d344e9803f 100644 > > --- a/arch/riscv/Kconfig > > +++ b/arch/riscv/Kconfig > > @@ -19,6 +19,7 @@ config RISCV > > select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2 > > select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE > > select ARCH_HAS_BINFMT_FLAT > > + select ARCH_HAS_CPU_FINALIZE_INIT > > select ARCH_HAS_CURRENT_STACK_POINTER > > select ARCH_HAS_DEBUG_VIRTUAL if MMU > > select ARCH_HAS_DEBUG_VM_PGTABLE > > @@ -525,6 +526,20 @@ config RISCV_ISA_SVPBMT > > > > If you don't know what to do here, say Y. > > > > +config RISCV_ISA_ZAWRS > > + bool "Zawrs extension support for wait-on-reservation-set instructions" > > + depends on RISCV_ALTERNATIVE > > + default y > > + help > > + Adds support to dynamically detect the presence of the Zawrs > > + extension and enable its usage. > > Drew, could you, in your update, use the wording: > Add support for enabling optimisations in the kernel when the > Zawrs extension is detected at boot.
How about
The Zawrs extension defines a pair of instructions to be used in polling loops which allow a hart to enter a low-power state or to trap to the hypervisor while waiting on a store to a memory location. Enable the use of these instructions when the Zawrs extension is detected at boot.
Thanks, drew
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