From e928e9cb3601ce240189bfea05b67ebd391c85ae Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Fri, 20 Mar 2015 20:39:41 +1100 Subject: 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 Signed-off-by: Paul Mackerras Signed-off-by: Alexander Graf --- arch/powerpc/platforms/powernv/rng.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'arch/powerpc/platforms') diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c index 80db43944afe..6eb808ff637e 100644 --- a/arch/powerpc/platforms/powernv/rng.c +++ b/arch/powerpc/platforms/powernv/rng.c @@ -24,12 +24,22 @@ struct powernv_rng { void __iomem *regs; + void __iomem *regs_real; unsigned long mask; }; static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng); +int powernv_hwrng_present(void) +{ + struct powernv_rng *rng; + + rng = get_cpu_var(powernv_rng); + put_cpu_var(rng); + return rng != NULL; +} + static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val) { unsigned long parity; @@ -46,6 +56,17 @@ static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val) return val; } +int powernv_get_random_real_mode(unsigned long *v) +{ + struct powernv_rng *rng; + + rng = raw_cpu_read(powernv_rng); + + *v = rng_whiten(rng, in_rm64(rng->regs_real)); + + return 1; +} + int powernv_get_random_long(unsigned long *v) { struct powernv_rng *rng; @@ -80,12 +101,20 @@ static __init void rng_init_per_cpu(struct powernv_rng *rng, static __init int rng_create(struct device_node *dn) { struct powernv_rng *rng; + struct resource res; unsigned long val; rng = kzalloc(sizeof(*rng), GFP_KERNEL); if (!rng) return -ENOMEM; + if (of_address_to_resource(dn, 0, &res)) { + kfree(rng); + return -ENXIO; + } + + rng->regs_real = (void __iomem *)res.start; + rng->regs = of_iomap(dn, 0); if (!rng->regs) { kfree(rng); -- cgit v1.2.2