[PATCH] riscv, bpf: Optimize zextw insn with Zba extension
Conor Dooley
conor at kernel.org
Fri May 10 13:56:07 PDT 2024
On Tue, May 07, 2024 at 06:45:28PM +0800, Xiao Wang wrote:
> The Zba extension provides add.uw insn which can be used to implement
> zext.w with rs2 set as ZERO.
>
> Signed-off-by: Xiao Wang <xiao.w.wang at intel.com>
> ---
> arch/riscv/Kconfig | 19 +++++++++++++++++++
> arch/riscv/net/bpf_jit.h | 18 ++++++++++++++++++
> 2 files changed, 37 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 6bec1bce6586..0679127cc0ea 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -586,6 +586,14 @@ config RISCV_ISA_V_PREEMPTIVE
> preemption. Enabling this config will result in higher memory
> consumption due to the allocation of per-task's kernel Vector context.
>
> +config TOOLCHAIN_HAS_ZBA
> + bool
> + default y
> + depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zba)
> + depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zba)
> + depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
> + depends on AS_HAS_OPTION_ARCH
> +
> config TOOLCHAIN_HAS_ZBB
> bool
> default y
> @@ -601,6 +609,17 @@ config TOOLCHAIN_HAS_VECTOR_CRYPTO
> def_bool $(as-instr, .option arch$(comma) +v$(comma) +zvkb)
> depends on AS_HAS_OPTION_ARCH
>
> +config RISCV_ISA_ZBA
> + bool "Zba extension support for bit manipulation instructions"
> + depends on TOOLCHAIN_HAS_ZBA
> + depends on RISCV_ALTERNATIVE
> + default y
> + help
> + Adds support to dynamically detect the presence of the ZBA
> + extension (address generation acceleration) and enable its usage.
Recently I sent some patches to reword other extensions' help text,
because the "add support to dynamically detect" had confused people a
bit. Dynamic detection is done regardless of config options for Zba.
The wording I went with in my patch for Zbb was:
Add support for enabling optimisations in the kernel when the
Zbb extension is detected at boot.
Could you use something similar here in the opening sentence please?
Thanks,
Conor.
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