From: Paul Mackerras <paulus@samba.org>
To: linuxppc-dev@ozlabs.org
Cc: tytso@mit.edu, keescook@chromium.org, hpa@linux.intel.com,
mpe@ellerman.id.au, mpm@selenic.com, herbert@gondor.apana.org.au
Subject: [PATCH v2] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_*
Date: Fri, 17 Jul 2015 20:11:43 +1000 [thread overview]
Message-ID: <20150717101143.GD5916@iris.ozlabs.ibm.com> (raw)
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(-)
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;
}
--
2.1.4
next reply other threads:[~2015-07-17 10:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-17 10:11 Paul Mackerras [this message]
2015-08-03 1:35 ` [v2] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_* Michael Ellerman
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