[PATCH v5 1/5] x86,kvm: Add MSR_KVM_GET_RNG_SEED and a matching feature bit

2014-07-23 Thread Andy Lutomirski 
This adds a simple interface to allow a guest to request 64 bits of
host nonblocking entropy.  This is independent of virtio-rng for a
couple of reasons:

 - It's intended to be usable during early boot, when a trivial
   synchronous interface is needed.

 - virtio-rng gives blocking entropy, and making guest boot wait for
   the host's /dev/random will cause problems.

MSR_KVM_GET_RNG_SEED is intended to provide 64 bits of best-effort
cryptographically secure data for use as a seed.  It provides no
guarantee that the result contains any actual entropy.

Signed-off-by: Andy Lutomirski 
---
 Documentation/virtual/kvm/cpuid.txt  | 3 +++
 arch/x86/include/uapi/asm/kvm_para.h | 2 ++
 arch/x86/kvm/cpuid.c | 3 ++-
 arch/x86/kvm/x86.c   | 4 
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/virtual/kvm/cpuid.txt 
b/Documentation/virtual/kvm/cpuid.txt
index 3c65feb..0ab043b 100644
--- a/Documentation/virtual/kvm/cpuid.txt
+++ b/Documentation/virtual/kvm/cpuid.txt
@@ -54,6 +54,9 @@ KVM_FEATURE_PV_UNHALT  || 7 || guest checks 
this feature bit
||   || before enabling paravirtualized
||   || spinlock support.
 --
+KVM_FEATURE_GET_RNG_SEED   || 8 || host provides rng seed data via
+   ||   || MSR_KVM_GET_RNG_SEED.
+--
 KVM_FEATURE_CLOCKSOURCE_STABLE_BIT ||24 || host will warn if no guest-side
||   || per-cpu warps are expected in
||   || kvmclock.
diff --git a/arch/x86/include/uapi/asm/kvm_para.h 
b/arch/x86/include/uapi/asm/kvm_para.h
index 94dc8ca..e2eaf93 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -24,6 +24,7 @@
 #define KVM_FEATURE_STEAL_TIME 5
 #define KVM_FEATURE_PV_EOI 6
 #define KVM_FEATURE_PV_UNHALT  7
+#define KVM_FEATURE_GET_RNG_SEED   8
 
 /* The last 8 bits are used to indicate how to interpret the flags field
  * in pvclock structure. If no bits are set, all flags are ignored.
@@ -40,6 +41,7 @@
 #define MSR_KVM_ASYNC_PF_EN 0x4b564d02
 #define MSR_KVM_STEAL_TIME  0x4b564d03
 #define MSR_KVM_PV_EOI_EN  0x4b564d04
+#define MSR_KVM_GET_RNG_SEED 0x4b564d05
 
 struct kvm_steal_time {
__u64 steal;
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 38a0afe..40d6763 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -479,7 +479,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 
*entry, u32 function,
 (1 << KVM_FEATURE_ASYNC_PF) |
 (1 << KVM_FEATURE_PV_EOI) |
 (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
-(1 << KVM_FEATURE_PV_UNHALT);
+(1 << KVM_FEATURE_PV_UNHALT) |
+(1 << KVM_FEATURE_GET_RNG_SEED);
 
if (sched_info_on())
entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f644933..4e81853 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -48,6 +48,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 
 #define CREATE_TRACE_POINTS
@@ -2480,6 +2481,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, 
u64 *pdata)
case MSR_KVM_PV_EOI_EN:
data = vcpu->arch.pv_eoi.msr_val;
break;
+   case MSR_KVM_GET_RNG_SEED:
+   get_random_bytes(&data, sizeof(data));
+   break;
case MSR_IA32_P5_MC_ADDR:
case MSR_IA32_P5_MC_TYPE:
case MSR_IA32_MCG_CAP:
-- 
1.9.3

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Re: [PATCH v5 1/5] x86,kvm: Add MSR_KVM_GET_RNG_SEED and a matching feature bit

2014-07-31 Thread Paolo Bonzini 
Il 24/07/2014 06:57, Andy Lutomirski ha scritto:
> This adds a simple interface to allow a guest to request 64 bits of
> host nonblocking entropy.  This is independent of virtio-rng for a
> couple of reasons:
> 
>  - It's intended to be usable during early boot, when a trivial
>synchronous interface is needed.
> 
>  - virtio-rng gives blocking entropy, and making guest boot wait for
>the host's /dev/random will cause problems.
> 
> MSR_KVM_GET_RNG_SEED is intended to provide 64 bits of best-effort
> cryptographically secure data for use as a seed.  It provides no
> guarantee that the result contains any actual entropy.
> 
> Signed-off-by: Andy Lutomirski 
> ---
>  Documentation/virtual/kvm/cpuid.txt  | 3 +++
>  arch/x86/include/uapi/asm/kvm_para.h | 2 ++
>  arch/x86/kvm/cpuid.c | 3 ++-
>  arch/x86/kvm/x86.c   | 4 
>  4 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/virtual/kvm/cpuid.txt 
> b/Documentation/virtual/kvm/cpuid.txt
> index 3c65feb..0ab043b 100644
> --- a/Documentation/virtual/kvm/cpuid.txt
> +++ b/Documentation/virtual/kvm/cpuid.txt
> @@ -54,6 +54,9 @@ KVM_FEATURE_PV_UNHALT  || 7 || guest checks 
> this feature bit
> ||   || before enabling 
> paravirtualized
> ||   || spinlock support.
>  
> --
> +KVM_FEATURE_GET_RNG_SEED   || 8 || host provides rng seed data 
> via
> +   ||   || MSR_KVM_GET_RNG_SEED.
> +--
>  KVM_FEATURE_CLOCKSOURCE_STABLE_BIT ||24 || host will warn if no 
> guest-side
> ||   || per-cpu warps are expected in
> ||   || kvmclock.
> diff --git a/arch/x86/include/uapi/asm/kvm_para.h 
> b/arch/x86/include/uapi/asm/kvm_para.h
> index 94dc8ca..e2eaf93 100644
> --- a/arch/x86/include/uapi/asm/kvm_para.h
> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> @@ -24,6 +24,7 @@
>  #define KVM_FEATURE_STEAL_TIME   5
>  #define KVM_FEATURE_PV_EOI   6
>  #define KVM_FEATURE_PV_UNHALT7
> +#define KVM_FEATURE_GET_RNG_SEED 8
>  
>  /* The last 8 bits are used to indicate how to interpret the flags field
>   * in pvclock structure. If no bits are set, all flags are ignored.
> @@ -40,6 +41,7 @@
>  #define MSR_KVM_ASYNC_PF_EN 0x4b564d02
>  #define MSR_KVM_STEAL_TIME  0x4b564d03
>  #define MSR_KVM_PV_EOI_EN  0x4b564d04
> +#define MSR_KVM_GET_RNG_SEED 0x4b564d05
>  
>  struct kvm_steal_time {
>   __u64 steal;
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 38a0afe..40d6763 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -479,7 +479,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 
> *entry, u32 function,
>(1 << KVM_FEATURE_ASYNC_PF) |
>(1 << KVM_FEATURE_PV_EOI) |
>(1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
> -  (1 << KVM_FEATURE_PV_UNHALT);
> +  (1 << KVM_FEATURE_PV_UNHALT) |
> +  (1 << KVM_FEATURE_GET_RNG_SEED);
>  
>   if (sched_info_on())
>   entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f644933..4e81853 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -48,6 +48,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  
>  #define CREATE_TRACE_POINTS
> @@ -2480,6 +2481,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, 
> u64 *pdata)
>   case MSR_KVM_PV_EOI_EN:
>   data = vcpu->arch.pv_eoi.msr_val;
>   break;
> + case MSR_KVM_GET_RNG_SEED:
> + get_random_bytes(&data, sizeof(data));
> + break;
>   case MSR_IA32_P5_MC_ADDR:
>   case MSR_IA32_P5_MC_TYPE:
>   case MSR_IA32_MCG_CAP:
> 

Acked-by: Paolo Bonzini 
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