linux-kernel - Re: [PATCH v5 1/4] RISC-V: add Zbc extension detection

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Message-ID: <20230612-unstable-tilt-1835f84363b1@spud>
Date:   Mon, 12 Jun 2023 22:31:14 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     palmer@...belt.com, paul.walmsley@...ive.com,
        aou@...s.berkeley.edu, herbert@...dor.apana.org.au,
        davem@...emloft.net, conor.dooley@...rochip.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, christoph.muellner@...ll.eu,
        Heiko Stuebner <heiko.stuebner@...ll.eu>
Subject: Re: [PATCH v5 1/4] RISC-V: add Zbc extension detection

Hey Heiko,

On Mon, Jun 12, 2023 at 11:04:39PM +0200, Heiko Stuebner wrote:
> From: Heiko Stuebner <heiko.stuebner@...ll.eu>
> 
> Add handling for Zbc extension.
> 
> Zbc provides instruction for carry-less multiplication.
> 
> Signed-off-by: Heiko Stuebner <heiko.stuebner@...ll.eu>
> ---
>  arch/riscv/Kconfig             | 22 ++++++++++++++++++++++
>  arch/riscv/include/asm/hwcap.h |  1 +
>  arch/riscv/kernel/cpu.c        |  1 +
>  arch/riscv/kernel/cpufeature.c |  1 +
>  4 files changed, 25 insertions(+)

Plumbing into the hwprobe stuff would be nice, but that's not a
requirement for getting stuff merged :)

> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index a3d54cd14fca..754cd154eca5 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -523,6 +523,28 @@ config RISCV_ISA_ZBB
>  
>  	   If you don't know what to do here, say Y.
>  
> +config TOOLCHAIN_HAS_ZBC
> +	bool
> +	default y
> +	depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zbc)
> +	depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zbc)
> +	depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
> +	depends on AS_IS_GNU
> +
> +config RISCV_ISA_ZBC
> +	bool "Zbc extension support for bit manipulation instructions"
> +	depends on TOOLCHAIN_HAS_ZBC
> +	depends on !XIP_KERNEL && MMU
> +	default y
> +	help
> +	   Adds support to dynamically detect the presence of the ZBC

Nit: s/ZBC/Zbc/

Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Cheers,
Conor.

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