Re: [PATCH v7 09/14] riscv: misaligned: move emulated access uniformity check in a function

From: Charlie Jenkins <charlie@rivosinc.com>
To: "Clément Léger" <cleger@rivosinc.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Anup Patel <anup@brainfault.org>,
	Atish Patra <atishp@atishpatra.org>,
	Shuah Khan <shuah@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org, kvm@vger.kernel.org,
	kvm-riscv@lists.infradead.org, linux-kselftest@vger.kernel.org,
	Samuel Holland <samuel.holland@sifive.com>,
	Andrew Jones <ajones@ventanamicro.com>,
	Deepak Gupta <debug@rivosinc.com>
Subject: Re: [PATCH v7 09/14] riscv: misaligned: move emulated access uniformity check in a function
Date: Mon, 19 May 2025 16:32:01 -0700	[thread overview]
Message-ID: <aCu_ce-kVQsyjrh5@ghost> (raw)
In-Reply-To: <20250515082217.433227-10-cleger@rivosinc.com>

On Thu, May 15, 2025 at 10:22:10AM +0200, Clément Léger wrote:
> Split the code that check for the uniformity of misaligned accesses
> performance on all cpus from check_unaligned_access_emulated_all_cpus()
> to its own function which will be used for delegation check. No
> functional changes intended.
> 
> Signed-off-by: Clément Léger <cleger@rivosinc.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> ---
>  arch/riscv/kernel/traps_misaligned.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
> index e551ba17f557..287ec37021c8 100644
> --- a/arch/riscv/kernel/traps_misaligned.c
> +++ b/arch/riscv/kernel/traps_misaligned.c
> @@ -647,6 +647,18 @@ bool __init check_vector_unaligned_access_emulated_all_cpus(void)
>  }
>  #endif
>  
> +static bool all_cpus_unaligned_scalar_access_emulated(void)
> +{
> +	int cpu;
> +
> +	for_each_online_cpu(cpu)
> +		if (per_cpu(misaligned_access_speed, cpu) !=

misaligned_access_speed is only defined when
CONFIG_RISCV_SCALAR_MISALIGNED. This function should return false when
!CONFIG_RISCV_SCALAR_MISALIGNED and only use this logic otherwise.

- Charlie

> +		    RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
> +			return false;
> +
> +	return true;
> +}
> +
>  #ifdef CONFIG_RISCV_SCALAR_MISALIGNED
>  
>  static bool unaligned_ctl __read_mostly;
> @@ -685,8 +697,6 @@ static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
>  
>  bool __init check_unaligned_access_emulated_all_cpus(void)
>  {
> -	int cpu;
> -
>  	/*
>  	 * We can only support PR_UNALIGN controls if all CPUs have misaligned
>  	 * accesses emulated since tasks requesting such control can run on any
> @@ -694,10 +704,8 @@ bool __init check_unaligned_access_emulated_all_cpus(void)
>  	 */
>  	on_each_cpu(check_unaligned_access_emulated, NULL, 1);
>  
> -	for_each_online_cpu(cpu)
> -		if (per_cpu(misaligned_access_speed, cpu)
> -		    != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
> -			return false;
> +	if (!all_cpus_unaligned_scalar_access_emulated())
> +		return false;
>  
>  	unaligned_ctl = true;
>  	return true;
> -- 
> 2.49.0
> 
> 
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