linux-kernel - Re: [PATCH 2/7] RISC-V: Detect Zicond from ISA string

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Message-ID: <20230920-36a5645f766ed9cce75a9e8c@orel>
Date:   Wed, 20 Sep 2023 09:44:30 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Anup Patel <apatel@...tanamicro.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Atish Patra <atishp@...shpatra.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Conor Dooley <conor@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Shuah Khan <shuah@...nel.org>,
        Mayuresh Chitale <mchitale@...tanamicro.com>,
        devicetree@...r.kernel.org, kvm@...r.kernel.org,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/7] RISC-V: Detect Zicond from ISA string

On Tue, Sep 19, 2023 at 09:23:38AM +0530, Anup Patel wrote:
> The RISC-V integer conditional (Zicond) operation extension defines
> standard conditional arithmetic and conditional-select/move operations
> which are inspired from the XVentanaCondOps extension. In fact, QEMU
> RISC-V also has support for emulating Zicond extension.
> 
> Let us detect Zicond extension from ISA string available through
> DT or ACPI.
> 
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> ---
>  Documentation/devicetree/bindings/riscv/extensions.yaml | 6 ++++++
>  arch/riscv/include/asm/hwcap.h                          | 1 +
>  arch/riscv/kernel/cpufeature.c                          | 1 +
>  3 files changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
> index cad8ef68eca7..7ea90e2dbc5b 100644
> --- a/Documentation/devicetree/bindings/riscv/extensions.yaml
> +++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
> @@ -225,6 +225,12 @@ properties:
>              ratified in the 20191213 version of the unprivileged ISA
>              specification.
>  
> +        - const: zicond
> +          description:
> +            The standard Zicond extension for conditional arithmetic and
> +            conditional-select/move operations as ratified in commit 8fb6694
> +            ("Update Gemfile") of riscv-zicond.

As of yesterday, v1.0 of the spec points at commit 95cf1f9 ("Add changes
requested by Ved during signoff")

> +
>          - const: zicsr
>            description: |
>              The standard Zicsr extension for control and status register
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index b7efe9e2fa89..15bafc02ffd4 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -60,6 +60,7 @@
>  #define RISCV_ISA_EXT_ZIHPM		42
>  #define RISCV_ISA_EXT_SMSTATEEN		43
>  #define RISCV_ISA_EXT_XVENTANACONDOPS	44
> +#define RISCV_ISA_EXT_ZICOND		45
>  
>  #define RISCV_ISA_EXT_MAX		64
>  
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 3a31d34fe709..49b6551f3347 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -174,6 +174,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_DATA(zba, RISCV_ISA_EXT_ZBA),
>  	__RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
>  	__RISCV_ISA_EXT_DATA(zbs, RISCV_ISA_EXT_ZBS),
> +	__RISCV_ISA_EXT_DATA(zicond, RISCV_ISA_EXT_ZICOND),

Zi extensions come before Zb extensions.

>  	__RISCV_ISA_EXT_DATA(smaia, RISCV_ISA_EXT_SMAIA),
>  	__RISCV_ISA_EXT_DATA(smstateen, RISCV_ISA_EXT_SMSTATEEN),
>  	__RISCV_ISA_EXT_DATA(ssaia, RISCV_ISA_EXT_SSAIA),
> -- 
> 2.34.1
>

Thanks,
drew