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: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

A lot of the code in platforms/pseries is using non-machine initcalls.
That means if a kernel built with pseries support runs on another
platform, for example powernv, the initcalls will still run.

Most of these cases are OK, though sometimes only due to luck. Some were
having more effect:

 * hcall_inst_init
  - Checking FW_FEATURE_LPAR which is set on ps3 & celleb.
 * mobility_sysfs_init
  - created sysfs files unconditionally
  - but no effect due to ENOSYS from rtas_ibm_suspend_me()
 * apo_pm_init
  - created sysfs, allows write
  - nothing checks the value written to though
 * alloc_dispatch_log_kmem_cache
  - creating kmem_cache on non-pseries machines
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

In commit a489043f "Implement arch_get_random_long() based on H_RANDOM" I
broke the SMP=n build. We were getting plpar_wrappers.h via spinlock.h
which breaks when SMP=n.
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Add support for the arch_get_random_long() hook based on the H_RANDOM
hypervisor call. We trust the hypervisor to provide us with random data,
ie. we don't whiten it in anyway.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>