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authorPaul Mackerras <paulus@samba.org>2015-07-17 20:11:43 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2015-07-23 19:52:03 +1000
commit01c9348c7620ec650aaeb3ce339f614709b2fb5a (patch)
tree519bbfcb73d48637750357676b3f024761dfa68d /arch/powerpc/perf
parent1c2cb594441d02815d304cccec9742ff5c707495 (diff)
powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_*
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> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/perf')
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