linux/Documentation/virtual
Michael Ellerman e928e9cb36 KVM: PPC: Book3S HV: Add fast real-mode H_RANDOM implementation.
Some PowerNV systems include a hardware random-number generator.
This HWRNG is present on POWER7+ and POWER8 chips and is capable of
generating one 64-bit random number every microsecond.  The random
numbers are produced by sampling a set of 64 unstable high-frequency
oscillators and are almost completely entropic.

PAPR defines an H_RANDOM hypercall which guests can use to obtain one
64-bit random sample from the HWRNG.  This adds a real-mode
implementation of the H_RANDOM hypercall.  This hypercall was
implemented in real mode because the latency of reading the HWRNG is
generally small compared to the latency of a guest exit and entry for
all the threads in the same virtual core.

Userspace can detect the presence of the HWRNG and the H_RANDOM
implementation by querying the KVM_CAP_PPC_HWRNG capability.  The
H_RANDOM hypercall implementation will only be invoked when the guest
does an H_RANDOM hypercall if userspace first enables the in-kernel
H_RANDOM implementation using the KVM_CAP_PPC_ENABLE_HCALL capability.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
2015-04-21 15:21:29 +02:00
..
kvm KVM: PPC: Book3S HV: Add fast real-mode H_RANDOM implementation. 2015-04-21 15:21:29 +02:00
uml sched: Rename sched.c as sched/core.c in comments and Documentation 2013-06-19 12:58:42 +02:00
00-INDEX virtual: Documentation: simplify and generalize paravirt_ops.txt 2015-02-13 17:15:44 +10:30
paravirt_ops.txt virtual: Documentation: simplify and generalize paravirt_ops.txt 2015-02-13 17:15:44 +10:30