| Message ID | 20150717101143.GD5916@iris.ozlabs.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Michael Ellerman |
| Headers | show |
On Fri, 2015-17-07 at 10:11:43 UTC, Paul Mackerras wrote: > The hardware RNG on POWER8 and POWER7+ can be relatively slow, since > it can only supply one 64-bit value per microsecond. Currently we > read it in arch_get_random_long(), but that slows down reading from > /dev/urandom since the code in random.c calls arch_get_random_long() > for every longword read from /dev/urandom. > > Since the hardware RNG supplies high-quality entropy on every read, it > matches the semantics of arch_get_random_seed_long() better than those > of arch_get_random_long(). Therefore this commit makes the code use > the POWER8/7+ hardware RNG only for arch_get_random_seed_{long,int} > and not for arch_get_random_{long,int}. > > This won't affect any other PowerPC-based platforms because none of > them currently support a hardware RNG. To make it clear that the > ppc_md function pointer is used for arch_get_random_seed_*, we rename > it from get_random_long to get_random_seed. > > Signed-off-by: Paul Mackerras <paulus@samba.org> Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/01c9348c7620ec650aae cheers
diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h index 0cc6eed..85e88f7 100644 --- a/arch/powerpc/include/asm/archrandom.h +++ b/arch/powerpc/include/asm/archrandom.h @@ -7,14 +7,23 @@ static inline int arch_get_random_long(unsigned long *v) { - if (ppc_md.get_random_long) - return ppc_md.get_random_long(v); - return 0; } static inline int arch_get_random_int(unsigned int *v) { + return 0; +} + +static inline int arch_get_random_seed_long(unsigned long *v) +{ + if (ppc_md.get_random_seed) + return ppc_md.get_random_seed(v); + + return 0; +} +static inline int arch_get_random_seed_int(unsigned int *v) +{ unsigned long val; int rc; @@ -27,22 +36,13 @@ static inline int arch_get_random_int(unsigned int *v) static inline int arch_has_random(void) { - return !!ppc_md.get_random_long; -} - -static inline int arch_get_random_seed_long(unsigned long *v) -{ - return 0; -} -static inline int arch_get_random_seed_int(unsigned int *v) -{ return 0; } + static inline int arch_has_random_seed(void) { - return 0; + return !!ppc_md.get_random_seed; } - #endif /* CONFIG_ARCH_RANDOM */ #ifdef CONFIG_PPC_POWERNV diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h index 952579f..cab6753 100644 --- a/arch/powerpc/include/asm/machdep.h +++ b/arch/powerpc/include/asm/machdep.h @@ -249,7 +249,7 @@ struct machdep_calls { #endif #ifdef CONFIG_ARCH_RANDOM - int (*get_random_long)(unsigned long *v); + int (*get_random_seed)(unsigned long *v); #endif }; diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c index 6eb808f..5dcbdea 100644 --- a/arch/powerpc/platforms/powernv/rng.c +++ b/arch/powerpc/platforms/powernv/rng.c @@ -128,7 +128,7 @@ static __init int rng_create(struct device_node *dn) pr_info_once("Registering arch random hook.\n"); - ppc_md.get_random_long = powernv_get_random_long; + ppc_md.get_random_seed = powernv_get_random_long; return 0; } diff --git a/arch/powerpc/platforms/pseries/rng.c b/arch/powerpc/platforms/pseries/rng.c index e096087..31ca557 100644 --- a/arch/powerpc/platforms/pseries/rng.c +++ b/arch/powerpc/platforms/pseries/rng.c @@ -38,7 +38,7 @@ static __init int rng_init(void) pr_info("Registering arch random hook.\n"); - ppc_md.get_random_long = pseries_get_random_long; + ppc_md.get_random_seed = pseries_get_random_long; return 0; }
The hardware RNG on POWER8 and POWER7+ can be relatively slow, since it can only supply one 64-bit value per microsecond. Currently we read it in arch_get_random_long(), but that slows down reading from /dev/urandom since the code in random.c calls arch_get_random_long() for every longword read from /dev/urandom. Since the hardware RNG supplies high-quality entropy on every read, it matches the semantics of arch_get_random_seed_long() better than those of arch_get_random_long(). Therefore this commit makes the code use the POWER8/7+ hardware RNG only for arch_get_random_seed_{long,int} and not for arch_get_random_{long,int}. This won't affect any other PowerPC-based platforms because none of them currently support a hardware RNG. To make it clear that the ppc_md function pointer is used for arch_get_random_seed_*, we rename it from get_random_long to get_random_seed. Signed-off-by: Paul Mackerras <paulus@samba.org> --- v2: Rename the ppc_md hook too. arch/powerpc/include/asm/archrandom.h | 28 ++++++++++++++-------------- arch/powerpc/include/asm/machdep.h | 2 +- arch/powerpc/platforms/powernv/rng.c | 2 +- arch/powerpc/platforms/pseries/rng.c | 2 +- 4 files changed, 17 insertions(+), 17 deletions(-)