Re: [PATCH v3 08/15] riscv: Add Zic64b to cpufeature and hwprobe

On Wed, Jun 03, 2026 at 07:12:03AM -0400, Guodong Xu wrote:
> Zic64b mandates 64-byte naturally aligned cache blocks and is a
> mandatory extension of the RVA22 and RVA23 profiles.  Allocate a
> RISCV_ISA_EXT_ZIC64B id, parse "zic64b" from the ISA string with a
> validate callback that requires cbom/cbop/cboz cache block sizes of 64
> bytes, and export it through hwprobe.
> 
> Signed-off-by: Guodong Xu <[email protected]>
> ---
> v3: New patch.
> ---
>  Documentation/arch/riscv/hwprobe.rst  |  3 +++
>  arch/riscv/include/asm/hwcap.h        |  1 +
>  arch/riscv/include/uapi/asm/hwprobe.h |  1 +
>  arch/riscv/kernel/cpufeature.c        | 18 ++++++++++++++++++
>  arch/riscv/kernel/sys_hwprobe.c       |  1 +
>  5 files changed, 24 insertions(+)
> 
> diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
> index 002d5046ab689..601e81f561421 100644
> --- a/Documentation/arch/riscv/hwprobe.rst
> +++ b/Documentation/arch/riscv/hwprobe.rst
> @@ -425,3 +425,6 @@ The following keys are defined:
>    * :c:macro:`RISCV_HWPROBE_EXT_B`: The B extension is supported, as defined
>      in version 1.0 of the Bit-Manipulation ISA extensions, and implies the
>      presence of the Zba, Zbb, and Zbs sub-extensions.

Need a blank line here.

> +  * :c:macro:`RISCV_HWPROBE_EXT_ZIC64B`: The Zic64b extension is supported,
> +    as defined in the RISC-V Profiles specification starting from commit
> +    b1d80660 ("Updated to ratified state.")
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index 58523b3a1998a..36572c1ff438a 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -117,6 +117,7 @@
>  #define RISCV_ISA_EXT_ZICCAMOA		107
>  #define RISCV_ISA_EXT_ZICCIF		108
>  #define RISCV_ISA_EXT_ZA64RS		109
> +#define RISCV_ISA_EXT_ZIC64B		110
>  
>  #define RISCV_ISA_EXT_XLINUXENVCFG	127
>  
> diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
> index 430dc49a82863..36ec8ab470423 100644
> --- a/arch/riscv/include/uapi/asm/hwprobe.h
> +++ b/arch/riscv/include/uapi/asm/hwprobe.h
> @@ -122,6 +122,7 @@ struct riscv_hwprobe {
>  #define		RISCV_HWPROBE_EXT_ZICCRSE	(1ULL << 4)
>  #define		RISCV_HWPROBE_EXT_ZA64RS	(1ULL << 5)
>  #define		RISCV_HWPROBE_EXT_B		(1ULL << 6)
> +#define		RISCV_HWPROBE_EXT_ZIC64B	(1ULL << 7)
>  
>  /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
>  
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index e0197160af6dd..79ff431768139 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -154,6 +154,23 @@ static int riscv_ext_zicbop_validate(const struct riscv_isa_ext_data *data,
>  	return 0;
>  }
>  
> +static int riscv_ext_zic64b_validate(const struct riscv_isa_ext_data *data,
> +				     const unsigned long *isa_bitmap)
> +{
> +	/*
> +	 * Zic64b mandates 64-byte naturally aligned cache blocks; cross-check the
> +	 * cbom/cbop/cboz block-size device-tree properties to avoid inconsistency.
> +	 */
> +	if (riscv_cbom_block_size != 64 ||
> +	    riscv_cbop_block_size != 64 ||
> +	    riscv_cboz_block_size != 64) {
> +		pr_err("Zic64b detected in ISA string, disabling as the cache block size is not 64 bytes\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
>  static int riscv_ext_f_validate(const struct riscv_isa_ext_data *data,
>  				const unsigned long *isa_bitmap)
>  {
> @@ -524,6 +541,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_SUPERSET(b, RISCV_ISA_EXT_B, riscv_b_exts),
>  	__RISCV_ISA_EXT_SUPERSET_VALIDATE(v, RISCV_ISA_EXT_V, riscv_v_exts, riscv_ext_vector_float_validate),
>  	__RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_H),
> +	__RISCV_ISA_EXT_DATA_VALIDATE(zic64b, RISCV_ISA_EXT_ZIC64B, riscv_ext_zic64b_validate),
>  	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts, riscv_ext_zicbom_validate),
>  	__RISCV_ISA_EXT_DATA_VALIDATE(zicbop, RISCV_ISA_EXT_ZICBOP, riscv_ext_zicbop_validate),
>  	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts, riscv_ext_zicboz_validate),
> diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> index dcc102bf8f183..3e80e5551ae0d 100644
> --- a/arch/riscv/kernel/sys_hwprobe.c
> +++ b/arch/riscv/kernel/sys_hwprobe.c
> @@ -211,6 +211,7 @@ static void hwprobe_isa_ext1(struct riscv_hwprobe *pair,
>  		EXT_KEY(isainfo->isa, ZICCRSE, pair->value, missing);
>  		EXT_KEY(isainfo->isa, ZA64RS, pair->value, missing);
>  		EXT_KEY(isainfo->isa, B, pair->value, missing);
> +		EXT_KEY(isainfo->isa, ZIC64B, pair->value, missing);
>  	}
>  
>  	/* Now turn off reporting features if any CPU is missing it. */
> 
> -- 
> 2.43.0
>

Other than the missing blank line,

Reviewed-by: Andrew Jones <[email protected]>