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| author | Michael Ellerman <michael@ellerman.id.au> | 2015-03-20 12:39:41 +0300 |
|---|---|---|
| committer | Alexander Graf <agraf@suse.de> | 2015-04-21 16:21:29 +0300 |
| commit | e928e9cb3601ce240189bfea05b67ebd391c85ae (patch) | |
| tree | d76d6501bea8ffe04a448e5a5660d8926f22b3b4 /arch/powerpc/kvm/powerpc.c | |
| parent | 99342cf8044420eebdf9297ca03a14cb6a7085a1 (diff) | |
| download | linux-e928e9cb3601ce240189bfea05b67ebd391c85ae.tar.xz | |
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>
Diffstat (limited to 'arch/powerpc/kvm/powerpc.c')
| -rw-r--r-- | arch/powerpc/kvm/powerpc.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index 24bfe401373e..55a4763d6d11 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -529,6 +529,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) 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 |