linux-kernel - Re: [PATCH 3/9] riscv: Fix check_unaligned_access_all

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Message-ID: <1dc6fc96-1a3e-46fa-84be-ef6952d4fc35@ghiti.fr>
Date: Thu, 13 Feb 2025 14:12:17 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Andrew Jones <ajones@...tanamicro.com>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Cc: paul.walmsley@...ive.com, palmer@...belt.com, charlie@...osinc.com,
 jesse@...osinc.com, Anup Patel <apatel@...tanamicro.com>
Subject: Re: [PATCH 3/9] riscv: Fix check_unaligned_access_all_cpus

On 07/02/2025 17:19, Andrew Jones wrote:
> check_vector_unaligned_access_emulated_all_cpus(), like its name
> suggests, will return true when all cpus emulate unaligned vector
> accesses. If the function returned false it may have been because
> vector isn't supported at all (!has_vector()) or because at least
> one cpu doesn't emulate unaligned vector accesses. Since false may
> be returned for two cases, checking for it isn't sufficient when
> attempting to determine if we should proceed with the vector speed
> check. Move the !has_vector() functionality to
> check_unaligned_access_all_cpus() in order for
> check_vector_unaligned_access_emulated_all_cpus() to return false
> for a single case.
>
> Fixes: e7c9d66e313b ("RISC-V: Report vector unaligned access speed hwprobe")
> Signed-off-by: Andrew Jones <ajones@...tanamicro.com>
> ---
>   arch/riscv/kernel/traps_misaligned.c       |  6 ------
>   arch/riscv/kernel/unaligned_access_speed.c | 11 +++++++----
>   2 files changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
> index aacbd9d7196e..4354c87c0376 100644
> --- a/arch/riscv/kernel/traps_misaligned.c
> +++ b/arch/riscv/kernel/traps_misaligned.c
> @@ -609,12 +609,6 @@ bool __init check_vector_unaligned_access_emulated_all_cpus(void)
>   {
>   	int cpu;
>   
> -	if (!has_vector()) {
> -		for_each_online_cpu(cpu)
> -			per_cpu(vector_misaligned_access, cpu) = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
> -		return false;
> -	}
> -
>   	schedule_on_each_cpu(check_vector_unaligned_access_emulated);
>   
>   	for_each_online_cpu(cpu)
> diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c
> index 161964cf2abc..02b485dc4bc4 100644
> --- a/arch/riscv/kernel/unaligned_access_speed.c
> +++ b/arch/riscv/kernel/unaligned_access_speed.c
> @@ -403,13 +403,16 @@ static int __init vec_check_unaligned_access_speed_all_cpus(void *unused __alway
>   
>   static int __init check_unaligned_access_all_cpus(void)
>   {
> -	bool all_cpus_emulated, all_cpus_vec_unsupported;
> +	bool all_cpus_emulated;
> +	int cpu;
>   
>   	all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
> -	all_cpus_vec_unsupported = check_vector_unaligned_access_emulated_all_cpus();
>   
> -	if (!all_cpus_vec_unsupported &&
> -	    IS_ENABLED(CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS)) {
> +	if (!has_vector()) {
> +		for_each_online_cpu(cpu)
> +			per_cpu(vector_misaligned_access, cpu) = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
> +	} else if (!check_vector_unaligned_access_emulated_all_cpus() &&
> +		   IS_ENABLED(CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS)) {
>   		kthread_run(vec_check_unaligned_access_speed_all_cpus,
>   			    NULL, "vec_check_unaligned_access_speed_all_cpus");
>   	}

Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks,

Alex