Re: [PATCH v2 4/4] random: Add arch_has_random[_seed]()

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Mon, 2014-03-17 at 16:36 -0700, H. Peter Anvin wrote:
> Add predicate functions for having arch_get_random[_seed]*().  The
> only current use is to avoid the loop in arch_random_refill() when
> arch_get_random_seed_long() is unavailable.

Paul, I think our HW rng on P7+ and later would qualify no ?

Cheers,
Ben.

> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <michael@ellerman.id.au>
> ---
>  arch/powerpc/include/asm/archrandom.h | 9 +++++++++
>  arch/x86/include/asm/archrandom.h     | 3 +++
>  drivers/char/random.c                 | 3 +++
>  include/linux/random.h                | 8 ++++++++
>  4 files changed, 23 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
> index 801beba..bde5311 100644
> --- a/arch/powerpc/include/asm/archrandom.h
> +++ b/arch/powerpc/include/asm/archrandom.h
> @@ -25,6 +25,11 @@ static inline int arch_get_random_int(unsigned int *v)
>  	return rc;
>  }
>  
> +static inline int arch_has_random(void)
> +{
> +	return !!ppc_md.get_random_long;
> +}
> +
>  int powernv_get_random_long(unsigned long *v);
>  
>  static inline int arch_get_random_seed_long(unsigned long *v)
> @@ -35,6 +40,10 @@ static inline int arch_get_random_seed_int(unsigned int *v)
>  {
>  	return 0;
>  }
> +static inline int arch_has_random_seed(void)
> +{
> +	return 0;
> +}
>  
>  #endif /* CONFIG_ARCH_RANDOM */
>  
> diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
> index ba064d5..c7ed4a6 100644
> --- a/arch/x86/include/asm/archrandom.h
> +++ b/arch/x86/include/asm/archrandom.h
> @@ -100,6 +100,9 @@ GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);
>  
>  #endif /* CONFIG_X86_64 */
>  
> +#define arch_has_random()	static_cpu_has(X86_FEATURE_RDRAND)
> +#define arch_has_random_seed()	static_cpu_has(X86_FEATURE_RDSEED)
> +
>  #endif  /* CONFIG_ARCH_RANDOM */
>  
>  extern void x86_init_rdrand(struct cpuinfo_x86 *c);
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index c35cee2..6b75713 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -1307,6 +1307,9 @@ static int arch_random_refill(void)
>  	unsigned int i;
>  	unsigned long buf[nlongs];
>  
> +	if (!arch_has_random_seed())
> +		return 0;
> +
>  	for (i = 0; i < nlongs; i++) {
>  		if (arch_get_random_seed_long(&buf[n]))
>  			n++;
> diff --git a/include/linux/random.h b/include/linux/random.h
> index ddaddec..e7a221a 100644
> --- a/include/linux/random.h
> +++ b/include/linux/random.h
> @@ -72,6 +72,10 @@ static inline int arch_get_random_int(unsigned int *v)
>  {
>  	return 0;
>  }
> +static inline int arch_has_random(void)
> +{
> +	return 0;
> +}
>  static inline int arch_get_random_seed_long(unsigned long *v)
>  {
>  	return 0;
> @@ -80,6 +84,10 @@ static inline int arch_get_random_seed_int(unsigned int *v)
>  {
>  	return 0;
>  }
> +static inline int arch_has_random_seed(void)
> +{
> +	return 0;
> +}
>  #endif
>  
>  /* Pseudo random number generator from numerical recipes. */