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>

6 files changed, 173 insertions, 2 deletions

diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
index bde531103638..0cc6eedc4780 100644
--- a/arch/powerpc/include/asm/archrandom.h
+++ b/arch/powerpc/include/asm/archrandom.h
@@ -30,8 +30,6 @@ static inline int arch_has_random(void)
         return !!ppc_md.get_random_long;
 }
 
-int powernv_get_random_long(unsigned long *v);
-
 static inline int arch_get_random_seed_long(unsigned long *v)
 {
         return 0;
@@ -47,4 +45,13 @@ static inline int arch_has_random_seed(void)
 
 #endif /* CONFIG_ARCH_RANDOM */
 
+#ifdef CONFIG_PPC_POWERNV
+int powernv_hwrng_present(void);
+int powernv_get_random_long(unsigned long *v);
+int powernv_get_random_real_mode(unsigned long *v);
+#else
+static inline int powernv_hwrng_present(void) { return 0; }
+static inline int powernv_get_random_real_mode(unsigned long *v) { return 0; }
+#endif
+
 #endif /* _ASM_POWERPC_ARCHRANDOM_H */
diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index 46bf652c9169..b8475daad884 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -302,6 +302,8 @@ static inline bool is_kvmppc_hv_enabled(struct kvm *kvm)
         return kvm->arch.kvm_ops == kvmppc_hv_ops;
 }
 
+extern int kvmppc_hwrng_present(void);
+
 /*
  * Cuts out inst bits with ordering according to spec.
  * That means the leftmost bit is zero. All given bits are included.
diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
index 1f083ff8a61a..1954a1c4b1f9 100644
--- a/arch/powerpc/kvm/book3s_hv_builtin.c
+++ b/arch/powerpc/kvm/book3s_hv_builtin.c
@@ -21,6 +21,7 @@
 #include <asm/cputable.h>
 #include <asm/kvm_ppc.h>
 #include <asm/kvm_book3s.h>
+#include <asm/archrandom.h>
 
 #define KVM_CMA_CHUNK_ORDER     18
 
@@ -169,3 +170,17 @@ int kvmppc_hcall_impl_hv_realmode(unsigned long cmd)
         return 0;
 }
 EXPORT_SYMBOL_GPL(kvmppc_hcall_impl_hv_realmode);
+
+int kvmppc_hwrng_present(void)
+{
+        return powernv_hwrng_present();
+}
+EXPORT_SYMBOL_GPL(kvmppc_hwrng_present);
+
+long kvmppc_h_random(struct kvm_vcpu *vcpu)
+{
+        if (powernv_get_random_real_mode(&vcpu->arch.gpr[4]))
+                return H_SUCCESS;
+
+        return H_HARDWARE;
+}
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 6cbf1630cb70..0814ca122fcd 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1839,6 +1839,121 @@ hcall_real_table:
         .long   0               /* 0x12c */
         .long   0               /* 0x130 */
         .long   DOTSYM(kvmppc_h_set_xdabr) - hcall_real_table
+        .long   0               /* 0x138 */
+        .long   0               /* 0x13c */
+        .long   0               /* 0x140 */
+        .long   0               /* 0x144 */
+        .long   0               /* 0x148 */
+        .long   0               /* 0x14c */
+        .long   0               /* 0x150 */
+        .long   0               /* 0x154 */
+        .long   0               /* 0x158 */
+        .long   0               /* 0x15c */
+        .long   0               /* 0x160 */
+        .long   0               /* 0x164 */
+        .long   0               /* 0x168 */
+        .long   0               /* 0x16c */
+        .long   0               /* 0x170 */
+        .long   0               /* 0x174 */
+        .long   0               /* 0x178 */
+        .long   0               /* 0x17c */
+        .long   0               /* 0x180 */
+        .long   0               /* 0x184 */
+        .long   0               /* 0x188 */
+        .long   0               /* 0x18c */
+        .long   0               /* 0x190 */
+        .long   0               /* 0x194 */
+        .long   0               /* 0x198 */
+        .long   0               /* 0x19c */
+        .long   0               /* 0x1a0 */
+        .long   0               /* 0x1a4 */
+        .long   0               /* 0x1a8 */
+        .long   0               /* 0x1ac */
+        .long   0               /* 0x1b0 */
+        .long   0               /* 0x1b4 */
+        .long   0               /* 0x1b8 */
+        .long   0               /* 0x1bc */
+        .long   0               /* 0x1c0 */
+        .long   0               /* 0x1c4 */
+        .long   0               /* 0x1c8 */
+        .long   0               /* 0x1cc */
+        .long   0               /* 0x1d0 */
+        .long   0               /* 0x1d4 */
+        .long   0               /* 0x1d8 */
+        .long   0               /* 0x1dc */
+        .long   0               /* 0x1e0 */
+        .long   0               /* 0x1e4 */
+        .long   0               /* 0x1e8 */
+        .long   0               /* 0x1ec */
+        .long   0               /* 0x1f0 */
+        .long   0               /* 0x1f4 */
+        .long   0               /* 0x1f8 */
+        .long   0               /* 0x1fc */
+        .long   0               /* 0x200 */
+        .long   0               /* 0x204 */
+        .long   0               /* 0x208 */
+        .long   0               /* 0x20c */
+        .long   0               /* 0x210 */
+        .long   0               /* 0x214 */
+        .long   0               /* 0x218 */
+        .long   0               /* 0x21c */
+        .long   0               /* 0x220 */
+        .long   0               /* 0x224 */
+        .long   0               /* 0x228 */
+        .long   0               /* 0x22c */
+        .long   0               /* 0x230 */
+        .long   0               /* 0x234 */
+        .long   0               /* 0x238 */
+        .long   0               /* 0x23c */
+        .long   0               /* 0x240 */
+        .long   0               /* 0x244 */
+        .long   0               /* 0x248 */
+        .long   0               /* 0x24c */
+        .long   0               /* 0x250 */
+        .long   0               /* 0x254 */
+        .long   0               /* 0x258 */
+        .long   0               /* 0x25c */
+        .long   0               /* 0x260 */
+        .long   0               /* 0x264 */
+        .long   0               /* 0x268 */
+        .long   0               /* 0x26c */
+        .long   0               /* 0x270 */
+        .long   0               /* 0x274 */
+        .long   0               /* 0x278 */
+        .long   0               /* 0x27c */
+        .long   0               /* 0x280 */
+        .long   0               /* 0x284 */
+        .long   0               /* 0x288 */
+        .long   0               /* 0x28c */
+        .long   0               /* 0x290 */
+        .long   0               /* 0x294 */
+        .long   0               /* 0x298 */
+        .long   0               /* 0x29c */
+        .long   0               /* 0x2a0 */
+        .long   0               /* 0x2a4 */
+        .long   0               /* 0x2a8 */
+        .long   0               /* 0x2ac */
+        .long   0               /* 0x2b0 */
+        .long   0               /* 0x2b4 */
+        .long   0               /* 0x2b8 */
+        .long   0               /* 0x2bc */
+        .long   0               /* 0x2c0 */
+        .long   0               /* 0x2c4 */
+        .long   0               /* 0x2c8 */
+        .long   0               /* 0x2cc */
+        .long   0               /* 0x2d0 */
+        .long   0               /* 0x2d4 */
+        .long   0               /* 0x2d8 */
+        .long   0               /* 0x2dc */
+        .long   0               /* 0x2e0 */
+        .long   0               /* 0x2e4 */
+        .long   0               /* 0x2e8 */
+        .long   0               /* 0x2ec */
+        .long   0               /* 0x2f0 */
+        .long   0               /* 0x2f4 */
+        .long   0               /* 0x2f8 */
+        .long   0               /* 0x2fc */
+        .long   DOTSYM(kvmppc_h_random) - hcall_real_table
         .globl  hcall_real_table_end
 hcall_real_table_end:
 
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
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);