Re: [v4 PATCH 1/2] [PowerPC] Add simd.h implementation

[Christophe Leroy <christophe.leroy@c-s.fr>]

Le 15/05/2019 à 03:37, Shawn Landden a écrit :
> Based off the x86 one.
> 
> WireGuard really wants to be able to do SIMD in interrupts,
> so it can accelerate its in-bound path.
> 
> Signed-off-by: Shawn Landden <shawn@git.icu>
> ---

Could you please as usual list here the changes provided by each version 
to ease the review ?

Thanks
Christophe

>   arch/powerpc/include/asm/simd.h | 17 +++++++++++++++++
>   arch/powerpc/kernel/process.c   | 30 ++++++++++++++++++++++++++++++
>   2 files changed, 47 insertions(+)
>   create mode 100644 arch/powerpc/include/asm/simd.h
> 
> diff --git a/arch/powerpc/include/asm/simd.h b/arch/powerpc/include/asm/simd.h
> new file mode 100644
> index 000000000..2fe26f258
> --- /dev/null
> +++ b/arch/powerpc/include/asm/simd.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +
> +/*
> + * may_use_simd - whether it is allowable at this time to issue SIMD
> + *                instructions or access the SIMD register file
> + *
> + * It's always ok in process context (ie "not interrupt")
> + * but it is sometimes ok even from an irq.
> + */
> +#ifdef CONFIG_PPC_FPU
> +extern bool may_use_simd(void);
> +#else
> +static inline bool may_use_simd(void)
> +{
> +	return false;
> +}
> +#endif
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index dd9e0d538..ef534831f 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -345,6 +345,36 @@ static int restore_altivec(struct task_struct *tsk)
>   	}
>   	return 0;
>   }
> +
> +/*
> + * Were we in user mode when we were
> + * interrupted?
> + *
> + * Doing kernel_altivec/vsx_begin/end() is ok if we are running
> + * in an interrupt context from user mode - we'll just
> + * save the FPU state as required.
> + */
> +static bool interrupted_user_mode(void)
> +{
> +	struct pt_regs *regs = get_irq_regs();
> +
> +	return regs && user_mode(regs);
> +}
> +
> +/*
> + * Can we use FPU in kernel mode with the
> + * whole "kernel_fpu/altivec/vsx_begin/end()" sequence?
> + *
> + * It's always ok in process context (ie "not interrupt")
> + * but it is sometimes ok even from an irq.
> + */
> +bool may_use_simd(void)
> +{
> +	return !in_interrupt() ||
> +		interrupted_user_mode();
> +}
> +EXPORT_SYMBOL(may_use_simd);
> +
>   #else
>   #define loadvec(thr) 0
>   static inline int restore_altivec(struct task_struct *tsk) { return 0; }
>