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>
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 24bfe40..55a4763 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -529,6 +529,9 @@
case KVM_CAP_PPC_RMA:
r = 0;
break;
+ case KVM_CAP_PPC_HWRNG:
+ r = kvmppc_hwrng_present();
+ break;
#endif
case KVM_CAP_SYNC_MMU:
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE