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 hardware RNG only for arch_get_random_seed_{long,int} and not for
arch_get_random_{long,int}.
Signed-off-by: Paul Mackerras <pau...@samba.org>
---
arch/powerpc/include/asm/archrandom.h | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/arch/powerpc/include/asm/archrandom.h
b/arch/powerpc/include/asm/archrandom.h
index 0cc6eed..a4c3f54 100644
--- a/arch/powerpc/include/asm/archrandom.h
+++ b/arch/powerpc/include/asm/archrandom.h
@@ -7,13 +7,22 @@
static inline int arch_get_random_long(unsigned 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_long)
return ppc_md.get_random_long(v);
return 0;
}
-
-static inline int arch_get_random_int(unsigned int *v)
+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_long;
}
-
#endif /* CONFIG_ARCH_RANDOM */
#ifdef CONFIG_PPC_POWERNV
--
2.1.4
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