linux-kernel - Re: [PATCH 3/3] RISC-V: hwprobe: Expose Zba and Zbb

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Message-ID: <20230429-gruffly-chrome-fd94628cc5ff@spud>
Date:   Sat, 29 Apr 2023 14:40:51 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Evan Green <evan@...osinc.com>
Cc:     Palmer Dabbelt <palmer@...osinc.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Bresticker <abrestic@...osinc.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Celeste Liu <coelacanthus@...look.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Heiko Stuebner <heiko.stuebner@...ll.eu>,
        Jonathan Corbet <corbet@....net>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH 3/3] RISC-V: hwprobe: Expose Zba and Zbb

On Fri, Apr 28, 2023 at 12:06:08PM -0700, Evan Green wrote:
> Add two new bits to the IMA_EXT_0 key for ZBA and ZBB extensions. These
> are accurately reported per CPU.
> 
> Signed-off-by: Evan Green <evan@...osinc.com>
> 
> ---
> 
>  Documentation/riscv/hwprobe.rst       |  7 +++++
>  arch/riscv/include/uapi/asm/hwprobe.h |  2 ++
>  arch/riscv/kernel/sys_riscv.c         | 43 ++++++++++++++++++++++-----
>  3 files changed, 45 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/riscv/hwprobe.rst b/Documentation/riscv/hwprobe.rst
> index 9f0dd62dcb5d..21f444a38359 100644
> --- a/Documentation/riscv/hwprobe.rst
> +++ b/Documentation/riscv/hwprobe.rst
> @@ -64,6 +64,13 @@ The following keys are defined:
>    * :c:macro:`RISCV_HWPROBE_IMA_C`: The C extension is supported, as defined
>      by version 2.2 of the RISC-V ISA manual.
>  
> +  * :c:macro:`RISCV_HWPROBE_EXT_ZBA`: The Zba address generation extension is
> +       supported, as defined in version 1.0 of the Bit-Manipulation ISA
> +       extensions.
> +
> +  * :c:macro:`RISCV_HWPROBE_IMA_ZBB`: The Zbb extension is supporte, as defined

Why is one EXT_ZBA and the other is IMA_ZBB? You do not use IMA below,
so I assume this is a copy-paste mistake.

Also, s/supporte/supported.

Otherwise, looks fine.
Cheers,
Conor.

> +       in version 1.0 of the Bit-Manipulation ISA extensions.
> +
>  * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: A bitmask that contains performance
>    information about the selected set of processors.
>  
> diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
> index 8d745a4ad8a2..ef3b060d4e8d 100644
> --- a/arch/riscv/include/uapi/asm/hwprobe.h
> +++ b/arch/riscv/include/uapi/asm/hwprobe.h
> @@ -25,6 +25,8 @@ struct riscv_hwprobe {
>  #define RISCV_HWPROBE_KEY_IMA_EXT_0	4
>  #define		RISCV_HWPROBE_IMA_FD		(1 << 0)
>  #define		RISCV_HWPROBE_IMA_C		(1 << 1)
> +#define		RISCV_HWPROBE_EXT_ZBA		(1 << 2)
> +#define		RISCV_HWPROBE_EXT_ZBB		(1 << 3)
>  #define RISCV_HWPROBE_KEY_CPUPERF_0	5
>  #define		RISCV_HWPROBE_MISALIGNED_UNKNOWN	(0 << 0)
>  #define		RISCV_HWPROBE_MISALIGNED_EMULATED	(1 << 0)
> diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
> index 5db29683ebee..adfcb6b64db7 100644
> --- a/arch/riscv/kernel/sys_riscv.c
> +++ b/arch/riscv/kernel/sys_riscv.c
> @@ -121,6 +121,41 @@ static void hwprobe_arch_id(struct riscv_hwprobe *pair,
>  	pair->value = id;
>  }
>  
> +static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
> +			     const struct cpumask *cpus)
> +{
> +	int cpu;
> +	u64 missing = 0;
> +
> +	pair->value = 0;
> +	if (has_fpu())
> +		pair->value |= RISCV_HWPROBE_IMA_FD;
> +
> +	if (riscv_isa_extension_available(NULL, c))
> +		pair->value |= RISCV_HWPROBE_IMA_C;
> +
> +	/*
> +	 * Loop through and record extensions that 1) anyone has, and 2) anyone
> +	 * doesn't have.
> +	 */
> +	for_each_cpu(cpu, cpus) {
> +		struct riscv_isainfo *isainfo = &hart_isa[cpu];
> +
> +		if (riscv_isa_extension_available(isainfo->isa, ZBA))
> +			pair->value |= RISCV_HWPROBE_EXT_ZBA;
> +		else
> +			missing |= RISCV_HWPROBE_EXT_ZBA;
> +
> +		if (riscv_isa_extension_available(isainfo->isa, ZBB))
> +			pair->value |= RISCV_HWPROBE_EXT_ZBB;
> +		else
> +			missing |= RISCV_HWPROBE_EXT_ZBB;
> +	}
> +
> +	/* Now turn off reporting features if any CPU is missing it. */
> +	pair->value &= ~missing;
> +}
> +
>  static u64 hwprobe_misaligned(const struct cpumask *cpus)
>  {
>  	int cpu;
> @@ -164,13 +199,7 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
>  		break;
>  
>  	case RISCV_HWPROBE_KEY_IMA_EXT_0:
> -		pair->value = 0;
> -		if (has_fpu())
> -			pair->value |= RISCV_HWPROBE_IMA_FD;
> -
> -		if (riscv_isa_extension_available(NULL, c))
> -			pair->value |= RISCV_HWPROBE_IMA_C;
> -
> +		hwprobe_isa_ext0(pair, cpus);
>  		break;
>  
>  	case RISCV_HWPROBE_KEY_CPUPERF_0:
> -- 
> 2.25.1
> 

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