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authorMichael Ellerman <michael@ellerman.id.au>2015-03-20 20:39:41 +1100
committerAlexander Graf <agraf@suse.de>2015-04-21 15:21:29 +0200
commite928e9cb3601ce240189bfea05b67ebd391c85ae (patch)
treed76d6501bea8ffe04a448e5a5660d8926f22b3b4 /arch/powerpc/platforms
parent99342cf8044420eebdf9297ca03a14cb6a7085a1 (diff)
downloadlinux-e928e9cb3601ce240189bfea05b67ebd391c85ae.tar.bz2
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/platforms')
-rw-r--r--arch/powerpc/platforms/powernv/rng.c29
1 files changed, 29 insertions, 0 deletions
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);