On Fri, May 23, 2025 at 12:19:27PM +0200, Clément Léger wrote:
> Checking for the delegability of the misaligned access trap is needed
> for the KVM FWFT extension implementation. Add a function to get the
> delegability of the misaligned trap exception.
>
> Signed-off-by: Clément Léger <cleger@xxxxxxxxxxxx>
> Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
Reviewed-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
Tested-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
> ---
> arch/riscv/include/asm/cpufeature.h | 6 ++++++
> arch/riscv/kernel/traps_misaligned.c | 17 +++++++++++++++--
> 2 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
> index 2bfa4ef383ed..fbd0e4306c93 100644
> --- a/arch/riscv/include/asm/cpufeature.h
> +++ b/arch/riscv/include/asm/cpufeature.h
> @@ -81,6 +81,12 @@ static inline bool unaligned_ctl_available(void)
>
> #if defined(CONFIG_RISCV_MISALIGNED)
> DECLARE_PER_CPU(long, misaligned_access_speed);
> +bool misaligned_traps_can_delegate(void);
> +#else
> +static inline bool misaligned_traps_can_delegate(void)
> +{
> + return false;
> +}
> #endif
>
> bool __init check_vector_unaligned_access_emulated_all_cpus(void);
> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
> index 7ecaa8103fe7..93043924fe6c 100644
> --- a/arch/riscv/kernel/traps_misaligned.c
> +++ b/arch/riscv/kernel/traps_misaligned.c
> @@ -724,10 +724,10 @@ static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
> }
> #endif
>
> -#ifdef CONFIG_RISCV_SBI
> -
> static bool misaligned_traps_delegated;
>
> +#ifdef CONFIG_RISCV_SBI
> +
> static int cpu_online_sbi_unaligned_setup(unsigned int cpu)
> {
> if (sbi_fwft_set(SBI_FWFT_MISALIGNED_EXC_DELEG, 1, 0) &&
> @@ -763,6 +763,7 @@ static int cpu_online_sbi_unaligned_setup(unsigned int cpu __always_unused)
> {
> return 0;
> }
> +
> #endif
>
> int cpu_online_unaligned_access_init(unsigned int cpu)
> @@ -775,3 +776,15 @@ int cpu_online_unaligned_access_init(unsigned int cpu)
>
> return cpu_online_check_unaligned_access_emulated(cpu);
> }
> +
> +bool misaligned_traps_can_delegate(void)
> +{
> + /*
> + * Either we successfully requested misaligned traps delegation for all
> + * CPUs, or the SBI does not implement the FWFT extension but delegated
> + * the exception by default.
> + */
> + return misaligned_traps_delegated ||
> + all_cpus_unaligned_scalar_access_emulated();
> +}
> +EXPORT_SYMBOL_GPL(misaligned_traps_can_delegate);
> --
> 2.49.0
>
