* [PATCH] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_*
@ 2015-07-16 12:12 Paul Mackerras
2015-07-17 4:44 ` Michael Ellerman
0 siblings, 1 reply; 5+ messages in thread
From: Paul Mackerras @ 2015-07-16 12:12 UTC (permalink / raw)
To: linuxppc-dev
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 <paulus@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
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_*
2015-07-16 12:12 [PATCH] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_* Paul Mackerras
@ 2015-07-17 4:44 ` Michael Ellerman
0 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2015-07-17 4:44 UTC (permalink / raw)
To: Paul Mackerras; +Cc: linuxppc-dev
On Thu, 2015-07-16 at 22:12 +1000, 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 hardware RNG only for arch_get_random_seed_{long,int} and not for
> arch_get_random_{long,int}.
>
> Signed-off-by: Paul Mackerras <paulus@samba.org>
Yep seems sensible.
Can you resend and CC some of the random folks, just in case they care.
eg: tytso@mit.edu, keescook@chromium.org, hpa@linux.intel.com.
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_*
@ 2015-07-17 9:15 Paul Mackerras
2015-07-17 9:37 ` Segher Boessenkool
0 siblings, 1 reply; 5+ messages in thread
From: Paul Mackerras @ 2015-07-17 9:15 UTC (permalink / raw)
To: linuxppc-dev; +Cc: tytso, keescook, hpa, mpe, mpm, herbert
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.
Signed-off-by: Paul Mackerras <paulus@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
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_*
2015-07-17 9:15 Paul Mackerras
@ 2015-07-17 9:37 ` Segher Boessenkool
2015-07-17 10:09 ` Paul Mackerras
0 siblings, 1 reply; 5+ messages in thread
From: Segher Boessenkool @ 2015-07-17 9:37 UTC (permalink / raw)
To: Paul Mackerras; +Cc: linuxppc-dev, tytso, herbert, mpm, hpa, keescook
On Fri, Jul 17, 2015 at 07:15:58PM +1000, Paul Mackerras wrote:
> @@ -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);
You probably want to change that last name (ppc_md.get_random_long) then?
Pretty confusing like this :-)
Segher
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_*
2015-07-17 9:37 ` Segher Boessenkool
@ 2015-07-17 10:09 ` Paul Mackerras
0 siblings, 0 replies; 5+ messages in thread
From: Paul Mackerras @ 2015-07-17 10:09 UTC (permalink / raw)
To: Segher Boessenkool; +Cc: linuxppc-dev, tytso, herbert, mpm, hpa, keescook
On Fri, Jul 17, 2015 at 04:37:57AM -0500, Segher Boessenkool wrote:
> On Fri, Jul 17, 2015 at 07:15:58PM +1000, Paul Mackerras wrote:
> > @@ -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);
>
> You probably want to change that last name (ppc_md.get_random_long) then?
> Pretty confusing like this :-)
Fair point. New patch coming.
Paul.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2015-07-17 10:11 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2015-07-16 12:12 [PATCH] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_* Paul Mackerras
2015-07-17 4:44 ` Michael Ellerman
-- strict thread matches above, loose matches on Subject: below --
2015-07-17 9:15 Paul Mackerras
2015-07-17 9:37 ` Segher Boessenkool
2015-07-17 10:09 ` Paul Mackerras
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).