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Commit e928e9cb authored by Michael Ellerman's avatar Michael Ellerman Committed by Alexander Graf
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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: default avatarMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
parent 99342cf8

Documentation/virtual/kvm/api.txt

+17 −0
Original line number Diff line number Diff line
@@ -3573,3 +3573,20 @@ struct { 
@ar   - access register number



KVM handlers should exit to userspace with rc = -EREMOTE.





8. Other capabilities.

----------------------



This section lists capabilities that give information about other

features of the KVM implementation.



8.1 KVM_CAP_PPC_HWRNG



Architectures: ppc



This capability, if KVM_CHECK_EXTENSION indicates that it is

available, means that that the kernel has an implementation of the

H_RANDOM hypercall backed by a hardware random-number generator.

If present, the kernel H_RANDOM handler can be enabled for guest use

with the KVM_CAP_PPC_ENABLE_HCALL capability.

arch/powerpc/include/asm/archrandom.h

+9 −2
Original line number Diff line number Diff line
@@ -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 */

arch/powerpc/include/asm/kvm_ppc.h

+2 −0
Original line number Diff line number Diff line
@@ -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.

arch/powerpc/kvm/book3s_hv_builtin.c

+15 −0
Original line number Diff line number Diff line
@@ -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;

}

arch/powerpc/kvm/book3s_hv_rmhandlers.S

+115 −0
Original line number Diff line number Diff line
@@ -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: