Re: [PATCH v3 03/11] riscv: add ISA parsing for Zca, Zcf, Zcd and Zcb

[Conor Dooley <conor@kernel.org>]

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On Tue, Apr 23, 2024 at 02:43:17PM +0200, Clément Léger wrote:
> The Zc* standard extension for code reduction introduces new extensions.
> This patch adds support for Zca, Zcf, Zcd and Zcb. Zce, Zcmt and Zcmp
> are left out of this patch since they are targeting microcontrollers/
> embedded CPUs instead of application processors.
> 
> Signed-off-by: Clément Léger <cleger@rivosinc.com>

The potential split aside, I think what's here makes sense.

Thanks,
Conor.

> ---
>  arch/riscv/include/asm/hwcap.h |  4 +++
>  arch/riscv/kernel/cpufeature.c | 47 +++++++++++++++++++++++++++++++++-
>  2 files changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index 543e3ea2da0e..b7551bad341b 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -82,6 +82,10 @@
>  #define RISCV_ISA_EXT_ZACAS		73
>  #define RISCV_ISA_EXT_XANDESPMU		74
>  #define RISCV_ISA_EXT_ZIMOP		75
> +#define RISCV_ISA_EXT_ZCA		76
> +#define RISCV_ISA_EXT_ZCB		77
> +#define RISCV_ISA_EXT_ZCD		78
> +#define RISCV_ISA_EXT_ZCF		79
>  
>  #define RISCV_ISA_EXT_XLINUXENVCFG	127
>  
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 6d238c8dbccf..24bf3fbc0578 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -107,6 +107,29 @@ static bool riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
>  	return true;
>  }
>  
> +static bool riscv_ext_zca_depends(const struct riscv_isa_ext_data *data,
> +				   const unsigned long *isa_bitmap)
> +{
> +	return __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZCA);
> +}
> +static bool riscv_ext_zcd_validate(const struct riscv_isa_ext_data *data,
> +				   const unsigned long *isa_bitmap)
> +{
> +	return __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZCA) &&
> +	       __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_d);
> +}
> +
> +static bool riscv_ext_zcf_validate(const struct riscv_isa_ext_data *data,
> +				   const unsigned long *isa_bitmap)
> +{
> +#ifdef CONFIG_64BIT
> +	return false;
> +#else
> +	return __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZCA) &&
> +	       __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_f);
> +#endif
> +}
> +
>  #define _RISCV_ISA_EXT_DATA(_name, _id, _subset_exts, _subset_exts_size, _validate) {	\
>  	.name = #_name,									\
>  	.property = #_name,								\
> @@ -118,6 +141,9 @@ static bool riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
>  
>  #define __RISCV_ISA_EXT_DATA(_name, _id) _RISCV_ISA_EXT_DATA(_name, _id, NULL, 0, NULL)
>  
> +#define __RISCV_ISA_EXT_DATA_VALIDATE(_name, _id, _validate) \
> +			_RISCV_ISA_EXT_DATA(_name, _id, NULL, 0, _validate)
> +
>  /* Used to declare pure "lasso" extension (Zk for instance) */
>  #define __RISCV_ISA_EXT_BUNDLE(_name, _bundled_exts) \
>  	_RISCV_ISA_EXT_DATA(_name, RISCV_ISA_EXT_INVALID, _bundled_exts, \
> @@ -209,6 +235,21 @@ static const unsigned int riscv_xlinuxenvcfg_exts[] = {
>  	RISCV_ISA_EXT_XLINUXENVCFG
>  };
>  
> +/*
> + * Zc* spec states that:
> + * - C always implies Zca
> + * - C+F implies Zcf (RV32 only)
> + * - C+D implies Zcd
> + *
> + * These extensions will be enabled and then validated depending on the
> + * availability of F/D RV32.
> + */
> +static const unsigned int riscv_c_exts[] = {
> +	RISCV_ISA_EXT_ZCA,
> +	RISCV_ISA_EXT_ZCF,
> +	RISCV_ISA_EXT_ZCD,
> +};
> +
>  /*
>   * The canonical order of ISA extension names in the ISA string is defined in
>   * chapter 27 of the unprivileged specification.
> @@ -255,7 +296,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_DATA(f, RISCV_ISA_EXT_f),
>  	__RISCV_ISA_EXT_DATA(d, RISCV_ISA_EXT_d),
>  	__RISCV_ISA_EXT_DATA(q, RISCV_ISA_EXT_q),
> -	__RISCV_ISA_EXT_DATA(c, RISCV_ISA_EXT_c),
> +	__RISCV_ISA_EXT_SUPERSET(c, RISCV_ISA_EXT_c, riscv_c_exts),
>  	__RISCV_ISA_EXT_DATA(v, RISCV_ISA_EXT_v),
>  	__RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h),
>  	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts,
> @@ -274,6 +315,10 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_DATA(zfa, RISCV_ISA_EXT_ZFA),
>  	__RISCV_ISA_EXT_DATA(zfh, RISCV_ISA_EXT_ZFH),
>  	__RISCV_ISA_EXT_DATA(zfhmin, RISCV_ISA_EXT_ZFHMIN),
> +	__RISCV_ISA_EXT_DATA(zca, RISCV_ISA_EXT_ZCA),
> +	__RISCV_ISA_EXT_DATA_VALIDATE(zcb, RISCV_ISA_EXT_ZCB, riscv_ext_zca_depends),
> +	__RISCV_ISA_EXT_DATA_VALIDATE(zcd, RISCV_ISA_EXT_ZCD, riscv_ext_zcd_validate),
> +	__RISCV_ISA_EXT_DATA_VALIDATE(zcf, RISCV_ISA_EXT_ZCF, riscv_ext_zcf_validate),
>  	__RISCV_ISA_EXT_DATA(zba, RISCV_ISA_EXT_ZBA),
>  	__RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
>  	__RISCV_ISA_EXT_DATA(zbc, RISCV_ISA_EXT_ZBC),
> -- 
> 2.43.0
> 

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