• Paul Mackerras's avatar
    powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_* · 01c9348c
    Paul Mackerras authored
    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: default avatarPaul Mackerras <paulus@samba.org>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    01c9348c
rng.c 3.02 KB