On Fri, May 23, 2025 at 12:19:26PM +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 <cle...@rivosinc.com>
> Reviewed-by: Andrew Jones <ajo...@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 f1b2af515592..7ecaa8103fe7 100644
> --- a/arch/riscv/kernel/traps_misaligned.c
> +++ b/arch/riscv/kernel/traps_misaligned.c
> @@ -645,6 +645,18 @@ 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) !=
> + RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
> + return false;
> +
> + return true;
> +}
This ends up wasting time when !CONFIG_RISCV_SCALAR_MISALIGNED since it
will always return false in that case. Maybe there is a way to simplify
the ifdefs and still have performant code, but I don't think this is a
big enough problem to prevent this patch from merging.
Reviewed-by: Charlie Jenkins <char...@rivosinc.com>
Tested-by: Charlie Jenkins <char...@rivosinc.com>
> +
> #ifdef CONFIG_RISCV_SCALAR_MISALIGNED
>
> static bool unaligned_ctl __read_mostly;
> @@ -683,8 +695,6 @@ 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
> @@ -692,10 +702,8 @@ 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
>
