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[patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall

Started byMarcelo Tosatti <mtosatti@redhat.com>
First post2017-01-24 18:20 +0100
Last post2017-01-25 14:00 +0100
Articles 6 — 2 participants

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  [patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall Marcelo Tosatti <mtosatti@redhat.com> - 2017-01-24 18:20 +0100
    Re: [patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall Paolo Bonzini <pbonzini@redhat.com> - 2017-01-25 13:40 +0100
      Re: [patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall Paolo Bonzini <pbonzini@redhat.com> - 2017-01-25 14:00 +0100
        Re: [patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall Marcelo Tosatti <mtosatti@redhat.com> - 2017-01-25 14:10 +0100
          Re: [patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall Paolo Bonzini <pbonzini@redhat.com> - 2017-01-25 14:20 +0100
      Re: [patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall Marcelo Tosatti <mtosatti@redhat.com> - 2017-01-25 14:00 +0100

#1566014 — [patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall

FromMarcelo Tosatti <mtosatti@redhat.com>
Date2017-01-24 18:20 +0100
Subject[patch 2/4] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall
Message-ID<t3cVc-76f-23@gated-at.bofh.it>
Add a hypercall to retrieve the host realtime clock
and the TSC value used to calculate that clock read.

Used to implement clock synchronization between
host and guest.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

---
 Documentation/virtual/kvm/hypercalls.txt |   33 ++++++++++++++++++++++++
 arch/x86/include/uapi/asm/kvm_para.h     |    9 ++++++
 arch/x86/kvm/x86.c                       |   41 +++++++++++++++++++++++++++++++
 include/uapi/linux/kvm_para.h            |    3 ++
 4 files changed, 86 insertions(+)

v2: improve documentation (Radim)
    change hypercall name to KVM_HC_CLOCK_PAIRING (Radim)
    increase padding size

Index: kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h
===================================================================
--- kvm-ptpdriver.orig/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
+++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:25.038258187 -0200
@@ -50,6 +50,15 @@
 	__u32 pad[11];
 };
 
+#define KVM_CLOCK_PAIRING_WALLCLOCK 0
+struct kvm_clock_offset {
+	__s64 sec;
+	__s64 nsec;
+	__u64 tsc;
+	__u32 flags;
+	__u32 pad[9];
+};
+
 #define KVM_STEAL_ALIGNMENT_BITS 5
 #define KVM_STEAL_VALID_BITS ((-1ULL << (KVM_STEAL_ALIGNMENT_BITS + 1)))
 #define KVM_STEAL_RESERVED_MASK (((1 << KVM_STEAL_ALIGNMENT_BITS) - 1 ) << 1)
Index: kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt
===================================================================
--- kvm-ptpdriver.orig/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:11.947240575 -0200
+++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:25.038258187 -0200
@@ -81,3 +81,36 @@
 same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
 specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
 is used in the hypercall for future use.
+
+
+6. KVM_HC_CLOCK_PAIRING
+------------------------
+Architecture: x86
+Status: active
+Purpose: Hypercall used to synchronize host and guest clocks.
+Usage:
+
+a0: guest physical address where host copies
+"struct kvm_clock_offset" structure.
+
+a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
+is supported (hosts CLOCK_REALTIME clock).
+
+		struct kvm_clock_offset {
+			__s64 sec;
+			__s64 nsec;
+			__u64 tsc;
+			__u32 flags;
+			__u32 pad[9];
+		};
+
+       Where:
+               * sec: seconds from clock_type clock.
+               * nsec: nanoseconds from clock_type clock.
+               * tsc: TSC value used to calculate sec/nsec pair
+                 (this hypercall only works when host uses TSC clocksource).
+               * flags: flags, unused (0) at the moment.
+
+Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
+or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
+
Index: kvm-ptpdriver/arch/x86/kvm/x86.c
===================================================================
--- kvm-ptpdriver.orig/arch/x86/kvm/x86.c	2017-01-13 16:43:20.898252596 -0200
+++ kvm-ptpdriver/arch/x86/kvm/x86.c	2017-01-13 16:43:25.041258191 -0200
@@ -6119,6 +6119,44 @@
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_halt);
 
+static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
+			       unsigned long clock_type)
+{
+	struct kvm_clock_offset *clock_offset;
+	struct timespec ts;
+	cycle_t cycle;
+	int ret;
+
+	if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
+		return -KVM_EOPNOTSUPP;
+
+	if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
+		return -KVM_EOPNOTSUPP;
+
+	clock_offset = kzalloc(sizeof(struct kvm_clock_offset), GFP_KERNEL);
+	if (clock_offset == NULL)
+		return -KVM_ENOMEM;
+
+	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
+		kfree(clock_offset);
+		return -KVM_EOPNOTSUPP;
+	}
+
+	clock_offset->sec = ts.tv_sec;
+	clock_offset->nsec = ts.tv_nsec;
+	clock_offset->tsc = kvm_read_l1_tsc(vcpu, cycle);
+	clock_offset->flags = 0;
+
+	ret = 0;
+	if (kvm_write_guest(vcpu->kvm, paddr, clock_offset,
+			      sizeof(struct kvm_clock_offset)))
+		ret = -KVM_EFAULT;
+
+	kfree(clock_offset);
+
+	return ret;
+}
+
 /*
  * kvm_pv_kick_cpu_op:  Kick a vcpu.
  *
@@ -6183,6 +6221,9 @@
 		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
 		ret = 0;
 		break;
+	case KVM_HC_CLOCK_PAIRING:
+		ret = kvm_pv_clock_pairing(vcpu, a0, a1);
+		break;
 	default:
 		ret = -KVM_ENOSYS;
 		break;
Index: kvm-ptpdriver/include/uapi/linux/kvm_para.h
===================================================================
--- kvm-ptpdriver.orig/include/uapi/linux/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
+++ kvm-ptpdriver/include/uapi/linux/kvm_para.h	2017-01-13 16:43:25.042258192 -0200
@@ -14,6 +14,8 @@
 #define KVM_EFAULT		EFAULT
 #define KVM_E2BIG		E2BIG
 #define KVM_EPERM		EPERM
+#define KVM_EOPNOTSUPP		EOPNOTSUPP
+#define KVM_ENOMEM		ENOMEM
 
 #define KVM_HC_VAPIC_POLL_IRQ		1
 #define KVM_HC_MMU_OP			2
@@ -23,6 +25,7 @@
 #define KVM_HC_MIPS_GET_CLOCK_FREQ	6
 #define KVM_HC_MIPS_EXIT_VM		7
 #define KVM_HC_MIPS_CONSOLE_OUTPUT	8
+#define KVM_HC_CLOCK_PAIRING		9
 
 /*
  * hypercalls use architecture specific

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#1566561

FromPaolo Bonzini <pbonzini@redhat.com>
Date2017-01-25 13:40 +0100
Message-ID<t3v1M-1KX-17@gated-at.bofh.it>
In reply to#1566014

On 24/01/2017 18:09, Marcelo Tosatti wrote:
> Add a hypercall to retrieve the host realtime clock
> and the TSC value used to calculate that clock read.
> 
> Used to implement clock synchronization between
> host and guest.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> ---
>  Documentation/virtual/kvm/hypercalls.txt |   33 ++++++++++++++++++++++++
>  arch/x86/include/uapi/asm/kvm_para.h     |    9 ++++++
>  arch/x86/kvm/x86.c                       |   41 +++++++++++++++++++++++++++++++
>  include/uapi/linux/kvm_para.h            |    3 ++
>  4 files changed, 86 insertions(+)
> 
> v2: improve documentation (Radim)
>     change hypercall name to KVM_HC_CLOCK_PAIRING (Radim)
>     increase padding size
> 
> Index: kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h
> ===================================================================
> --- kvm-ptpdriver.orig/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
> +++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:25.038258187 -0200
> @@ -50,6 +50,15 @@
>  	__u32 pad[11];
>  };
>  
> +#define KVM_CLOCK_PAIRING_WALLCLOCK 0
> +struct kvm_clock_offset {

The struct still has the old name.

> +	__s64 sec;
> +	__s64 nsec;
> +	__u64 tsc;
> +	__u32 flags;
> +	__u32 pad[9];
> +};
> +
>  #define KVM_STEAL_ALIGNMENT_BITS 5
>  #define KVM_STEAL_VALID_BITS ((-1ULL << (KVM_STEAL_ALIGNMENT_BITS + 1)))
>  #define KVM_STEAL_RESERVED_MASK (((1 << KVM_STEAL_ALIGNMENT_BITS) - 1 ) << 1)
> Index: kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt
> ===================================================================
> --- kvm-ptpdriver.orig/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:11.947240575 -0200
> +++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:25.038258187 -0200
> @@ -81,3 +81,36 @@
>  same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
>  specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
>  is used in the hypercall for future use.
> +
> +
> +6. KVM_HC_CLOCK_PAIRING
> +------------------------
> +Architecture: x86
> +Status: active
> +Purpose: Hypercall used to synchronize host and guest clocks.
> +Usage:
> +
> +a0: guest physical address where host copies
> +"struct kvm_clock_offset" structure.
> +
> +a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
> +is supported (hosts CLOCK_REALTIME clock).
> +
> +		struct kvm_clock_offset {

Name of the struct not adjusted.
> +			__s64 sec;
> +			__s64 nsec;
> +			__u64 tsc;
> +			__u32 flags;
> +			__u32 pad[9];

I'd just leave one element of padding and put the struct on the stack, 
since we have no reason to think we'll need a lot of padding.

> +		};
> +
> +       Where:
> +               * sec: seconds from clock_type clock.
> +               * nsec: nanoseconds from clock_type clock.
> +               * tsc: TSC value used to calculate sec/nsec pair
> +                 (this hypercall only works when host uses TSC clocksource).

This is already mentioned below, and it's not clear that tsc is a guest 
TSC value.

> +               * flags: flags, unused (0) at the moment.
> +
> +Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
> +or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
> +
> Index: kvm-ptpdriver/arch/x86/kvm/x86.c
> ===================================================================
> --- kvm-ptpdriver.orig/arch/x86/kvm/x86.c	2017-01-13 16:43:20.898252596 -0200
> +++ kvm-ptpdriver/arch/x86/kvm/x86.c	2017-01-13 16:43:25.041258191 -0200
> @@ -6119,6 +6119,44 @@
>  }
>  EXPORT_SYMBOL_GPL(kvm_emulate_halt);
>  
> +static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
> +			       unsigned long clock_type)
> +{
> +	struct kvm_clock_offset *clock_offset;
> +	struct timespec ts;
> +	cycle_t cycle;
> +	int ret;
> +
> +	if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
> +		return -KVM_EOPNOTSUPP;
> +
> +	if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
> +		return -KVM_EOPNOTSUPP;

Already checked in kvm_get_walltime_and_clockread.

> +	clock_offset = kzalloc(sizeof(struct kvm_clock_offset), GFP_KERNEL);
> +	if (clock_offset == NULL)
> +		return -KVM_ENOMEM;
> +
> +	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
> +		kfree(clock_offset);
> +		return -KVM_EOPNOTSUPP;
> +	}
> +	clock_offset->sec = ts.tv_sec;
> +	clock_offset->nsec = ts.tv_nsec;
> +	clock_offset->tsc = kvm_read_l1_tsc(vcpu, cycle);
> +	clock_offset->flags = 0;
> +
> +	ret = 0;
> +	if (kvm_write_guest(vcpu->kvm, paddr, clock_offset,
> +			      sizeof(struct kvm_clock_offset)))
> +		ret = -KVM_EFAULT;
> +
> +	kfree(clock_offset);
> +
> +	return ret;
> +}
> +
>  /*
>   * kvm_pv_kick_cpu_op:  Kick a vcpu.
>   *
> @@ -6183,6 +6221,9 @@
>  		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
>  		ret = 0;
>  		break;
> +	case KVM_HC_CLOCK_PAIRING:
> +		ret = kvm_pv_clock_pairing(vcpu, a0, a1);
> +		break;
>  	default:
>  		ret = -KVM_ENOSYS;
>  		break;
> Index: kvm-ptpdriver/include/uapi/linux/kvm_para.h
> ===================================================================
> --- kvm-ptpdriver.orig/include/uapi/linux/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
> +++ kvm-ptpdriver/include/uapi/linux/kvm_para.h	2017-01-13 16:43:25.042258192 -0200
> @@ -14,6 +14,8 @@
>  #define KVM_EFAULT		EFAULT
>  #define KVM_E2BIG		E2BIG
>  #define KVM_EPERM		EPERM
> +#define KVM_EOPNOTSUPP		EOPNOTSUPP
> +#define KVM_ENOMEM		ENOMEM

This file could potentially be used across multiple architectures (it's 
not in arch/x86/include/uapi/asm), but EOPNOTSUPP is not the same on 
all systems.  Better use "95" which is the value it has on x86.

All this gives:

diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
index 55eb3e1ca494..cd35de84999f 100644
--- a/Documentation/virtual/kvm/hypercalls.txt
+++ b/Documentation/virtual/kvm/hypercalls.txt
@@ -94,9 +94,9 @@ a0: guest physical address where host copies
 "struct kvm_clock_offset" structure.
 
 a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
-is supported (hosts CLOCK_REALTIME clock).
+is supported (corresponding to the host's CLOCK_REALTIME clock).
 
-		struct kvm_clock_offset {
+		struct kvm_clock_pairing {
 			__s64 sec;
 			__s64 nsec;
 			__u64 tsc;
@@ -107,10 +107,12 @@ is supported (hosts CLOCK_REALTIME clock).
        Where:
                * sec: seconds from clock_type clock.
                * nsec: nanoseconds from clock_type clock.
-               * tsc: TSC value used to calculate sec/nsec pair
-                 (this hypercall only works when host uses TSC clocksource).
+               * tsc: guest TSC value used to calculate sec/nsec pair
                * flags: flags, unused (0) at the moment.
 
+The hypercall lets a guest compute a precise timestamp across
+host and guest.  The guest can use the returned TSC value to
+compute the CLOCK_REALTIME for its clock, at the same instant.
+
 Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
 or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
-
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index ce7b411e28bc..3641d8b7dba9 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -51,12 +51,12 @@ struct kvm_steal_time {
 };
 
 #define KVM_CLOCK_PAIRING_WALLCLOCK 0
-struct kvm_clock_offset {
+struct kvm_clock_pairing {
 	__s64 sec;
 	__s64 nsec;
 	__u64 tsc;
 	__u32 flags;
-	__u32 pad[9];
+	__u32 pad[1];
 };
 
 #define KVM_STEAL_ALIGNMENT_BITS 5
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4ecc3145ea4b..09e5d31dac98 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6149,9 +6149,9 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
 EXPORT_SYMBOL_GPL(kvm_emulate_halt);
 
 static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
-			       unsigned long clock_type)
+			        unsigned long clock_type)
 {
-	struct kvm_clock_offset *clock_offset;
+	struct kvm_clock_pairing clock_pairing;
 	struct timespec ts;
 	cycle_t cycle;
 	int ret;
@@ -6159,30 +6159,19 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
 	if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
 		return -KVM_EOPNOTSUPP;
 
-	if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
-		return -KVM_EOPNOTSUPP;
-
-	clock_offset = kzalloc(sizeof(struct kvm_clock_offset), GFP_KERNEL);
-	if (clock_offset == NULL)
-		return -KVM_ENOMEM;
-
-	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
-		kfree(clock_offset);
+	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false)
 		return -KVM_EOPNOTSUPP;
-	}
 
-	clock_offset->sec = ts.tv_sec;
-	clock_offset->nsec = ts.tv_nsec;
-	clock_offset->tsc = kvm_read_l1_tsc(vcpu, cycle);
-	clock_offset->flags = 0;
+	clock_pairing.sec = ts.tv_sec;
+	clock_pairing.nsec = ts.tv_nsec;
+	clock_pairing.tsc = kvm_read_l1_tsc(vcpu, cycle);
+	clock_pairing.flags = 0;
 
 	ret = 0;
-	if (kvm_write_guest(vcpu->kvm, paddr, clock_offset,
-			      sizeof(struct kvm_clock_offset)))
+	if (kvm_write_guest(vcpu->kvm, paddr, &clock_pairing,
+			    sizeof(struct kvm_clock_pairing)))
 		ret = -KVM_EFAULT;
 
-	kfree(clock_offset);
-
 	return ret;
 }
 
diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
index 68da60e7f519..c72128527377 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -14,7 +14,7 @@
 #define KVM_EFAULT		EFAULT
 #define KVM_E2BIG		E2BIG
 #define KVM_EPERM		EPERM
-#define KVM_EOPNOTSUPP		EOPNOTSUPP
+#define KVM_EOPNOTSUPP		95
 #define KVM_ENOMEM		ENOMEM
 
 #define KVM_HC_VAPIC_POLL_IRQ		1

Okay?

Paolo

>  #define KVM_HC_VAPIC_POLL_IRQ		1
>  #define KVM_HC_MMU_OP			2
> @@ -23,6 +25,7 @@
>  #define KVM_HC_MIPS_GET_CLOCK_FREQ	6
>  #define KVM_HC_MIPS_EXIT_VM		7
>  #define KVM_HC_MIPS_CONSOLE_OUTPUT	8
> +#define KVM_HC_CLOCK_PAIRING		9
>  
>  /*
>   * hypercalls use architecture specific
> 
> 
>

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#1566570

FromPaolo Bonzini <pbonzini@redhat.com>
Date2017-01-25 14:00 +0100
Message-ID<t3vl9-1RZ-33@gated-at.bofh.it>
In reply to#1566561

On 25/01/2017 13:55, Marcelo Tosatti wrote:
> On Wed, Jan 25, 2017 at 01:30:49PM +0100, Paolo Bonzini wrote:
>>
>>
>> On 24/01/2017 18:09, Marcelo Tosatti wrote:
>>> Add a hypercall to retrieve the host realtime clock
>>> and the TSC value used to calculate that clock read.
>>>
>>> Used to implement clock synchronization between
>>> host and guest.
>>>
>>> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>>>
>>> ---
>>>  Documentation/virtual/kvm/hypercalls.txt |   33 ++++++++++++++++++++++++
>>>  arch/x86/include/uapi/asm/kvm_para.h     |    9 ++++++
>>>  arch/x86/kvm/x86.c                       |   41 +++++++++++++++++++++++++++++++
>>>  include/uapi/linux/kvm_para.h            |    3 ++
>>>  4 files changed, 86 insertions(+)
>>>
>>> v2: improve documentation (Radim)
>>>     change hypercall name to KVM_HC_CLOCK_PAIRING (Radim)
>>>     increase padding size
>>>
>>> Index: kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h
>>> ===================================================================
>>> --- kvm-ptpdriver.orig/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
>>> +++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:25.038258187 -0200
>>> @@ -50,6 +50,15 @@
>>>  	__u32 pad[11];
>>>  };
>>>  
>>> +#define KVM_CLOCK_PAIRING_WALLCLOCK 0
>>> +struct kvm_clock_offset {
>>
>> The struct still has the old name.
>>
>>> +	__s64 sec;
>>> +	__s64 nsec;
>>> +	__u64 tsc;
>>> +	__u32 flags;
>>> +	__u32 pad[9];
>>> +};
> 
> That was on purpose: "to pair" is the operation. 
> 
> "struct kvm_clock_pairing" makes no sense to me 
> (because pairing is an "action").
> 
> (if you'd prefer that name, let me know).

A "pairing" is a union of two things, in this case a sec/nsec value and
a TSC value.  (I had to look it up in the dictionary though :)).

>>>  #define KVM_STEAL_ALIGNMENT_BITS 5
>>>  #define KVM_STEAL_VALID_BITS ((-1ULL << (KVM_STEAL_ALIGNMENT_BITS + 1)))
>>>  #define KVM_STEAL_RESERVED_MASK (((1 << KVM_STEAL_ALIGNMENT_BITS) - 1 ) << 1)
>>> Index: kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt
>>> ===================================================================
>>> --- kvm-ptpdriver.orig/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:11.947240575 -0200
>>> +++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:25.038258187 -0200
>>> @@ -81,3 +81,36 @@
>>>  same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
>>>  specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
>>>  is used in the hypercall for future use.
>>> +
>>> +
>>> +6. KVM_HC_CLOCK_PAIRING
>>> +------------------------
>>> +Architecture: x86
>>> +Status: active
>>> +Purpose: Hypercall used to synchronize host and guest clocks.
>>> +Usage:
>>> +
>>> +a0: guest physical address where host copies
>>> +"struct kvm_clock_offset" structure.
>>> +
>>> +a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
>>> +is supported (hosts CLOCK_REALTIME clock).
>>> +
>>> +		struct kvm_clock_offset {
>>
>> Name of the struct not adjusted.
>>> +			__s64 sec;
>>> +			__s64 nsec;
>>> +			__u64 tsc;
>>> +			__u32 flags;
>>> +			__u32 pad[9];
>>
>> I'd just leave one element of padding and put the struct on the stack, 
>> since we have no reason to think we'll need a lot of padding.
> 
> Well you don't know: we could implement it in case of HPET clocksource
> hosts.

But then the guest wouldn't have a TSC value to use, would it?

Also, how would it use more padding?

Paolo

>>> +		};
>>> +
>>> +       Where:
>>> +               * sec: seconds from clock_type clock.
>>> +               * nsec: nanoseconds from clock_type clock.
>>> +               * tsc: TSC value used to calculate sec/nsec pair
>>> +                 (this hypercall only works when host uses TSC clocksource).
>>
>> This is already mentioned below, and it's not clear that tsc is a guest 
>> TSC value.
> 
> Ok fixed.
> 
>>> +               * flags: flags, unused (0) at the moment.
>>> +
>>> +Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
>>> +or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
>>> +
>>> Index: kvm-ptpdriver/arch/x86/kvm/x86.c
>>> ===================================================================
>>> --- kvm-ptpdriver.orig/arch/x86/kvm/x86.c	2017-01-13 16:43:20.898252596 -0200
>>> +++ kvm-ptpdriver/arch/x86/kvm/x86.c	2017-01-13 16:43:25.041258191 -0200
>>> @@ -6119,6 +6119,44 @@
>>>  }
>>>  EXPORT_SYMBOL_GPL(kvm_emulate_halt);
>>>  
>>> +static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
>>> +			       unsigned long clock_type)
>>> +{
>>> +	struct kvm_clock_offset *clock_offset;
>>> +	struct timespec ts;
>>> +	cycle_t cycle;
>>> +	int ret;
>>> +
>>> +	if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
>>> +		return -KVM_EOPNOTSUPP;
>>> +
>>> +	if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
>>> +		return -KVM_EOPNOTSUPP;
>>
>> Already checked in kvm_get_walltime_and_clockread.
> 
> Fixed.
> 
>>> +	clock_offset = kzalloc(sizeof(struct kvm_clock_offset), GFP_KERNEL);
>>> +	if (clock_offset == NULL)
>>> +		return -KVM_ENOMEM;
>>> +
>>> +	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
>>> +		kfree(clock_offset);
>>> +		return -KVM_EOPNOTSUPP;
>>> +	}
>>> +	clock_offset->sec = ts.tv_sec;
>>> +	clock_offset->nsec = ts.tv_nsec;
>>> +	clock_offset->tsc = kvm_read_l1_tsc(vcpu, cycle);
>>> +	clock_offset->flags = 0;
>>> +
>>> +	ret = 0;
>>> +	if (kvm_write_guest(vcpu->kvm, paddr, clock_offset,
>>> +			      sizeof(struct kvm_clock_offset)))
>>> +		ret = -KVM_EFAULT;
>>> +
>>> +	kfree(clock_offset);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>>  /*
>>>   * kvm_pv_kick_cpu_op:  Kick a vcpu.
>>>   *
>>> @@ -6183,6 +6221,9 @@
>>>  		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
>>>  		ret = 0;
>>>  		break;
>>> +	case KVM_HC_CLOCK_PAIRING:
>>> +		ret = kvm_pv_clock_pairing(vcpu, a0, a1);
>>> +		break;
>>>  	default:
>>>  		ret = -KVM_ENOSYS;
>>>  		break;
>>> Index: kvm-ptpdriver/include/uapi/linux/kvm_para.h
>>> ===================================================================
>>> --- kvm-ptpdriver.orig/include/uapi/linux/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
>>> +++ kvm-ptpdriver/include/uapi/linux/kvm_para.h	2017-01-13 16:43:25.042258192 -0200
>>> @@ -14,6 +14,8 @@
>>>  #define KVM_EFAULT		EFAULT
>>>  #define KVM_E2BIG		E2BIG
>>>  #define KVM_EPERM		EPERM
>>> +#define KVM_EOPNOTSUPP		EOPNOTSUPP
>>> +#define KVM_ENOMEM		ENOMEM
>>
>> This file could potentially be used across multiple architectures (it's 
>> not in arch/x86/include/uapi/asm), but EOPNOTSUPP is not the same on 
>> all systems.  Better use "95" which is the value it has on x86.
> 
> Fixed.
> 
>> All this gives:
>>
>> diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
>> index 55eb3e1ca494..cd35de84999f 100644
>> --- a/Documentation/virtual/kvm/hypercalls.txt
>> +++ b/Documentation/virtual/kvm/hypercalls.txt
>> @@ -94,9 +94,9 @@ a0: guest physical address where host copies
>>  "struct kvm_clock_offset" structure.
>>  
>>  a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
>> -is supported (hosts CLOCK_REALTIME clock).
>> +is supported (corresponding to the host's CLOCK_REALTIME clock).
>>  
>> -		struct kvm_clock_offset {
>> +		struct kvm_clock_pairing {
>>  			__s64 sec;
>>  			__s64 nsec;
>>  			__u64 tsc;
>> @@ -107,10 +107,12 @@ is supported (hosts CLOCK_REALTIME clock).
>>         Where:
>>                 * sec: seconds from clock_type clock.
>>                 * nsec: nanoseconds from clock_type clock.
>> -               * tsc: TSC value used to calculate sec/nsec pair
>> -                 (this hypercall only works when host uses TSC clocksource).
>> +               * tsc: guest TSC value used to calculate sec/nsec pair
>>                 * flags: flags, unused (0) at the moment.
>>  
>> +The hypercall lets a guest compute a precise timestamp across
>> +host and guest.  The guest can use the returned TSC value to
>> +compute the CLOCK_REALTIME for its clock, at the same instant.
>> +
>>  Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
>>  or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
>> -
>> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
>> index ce7b411e28bc..3641d8b7dba9 100644
>> --- a/arch/x86/include/uapi/asm/kvm_para.h
>> +++ b/arch/x86/include/uapi/asm/kvm_para.h
>> @@ -51,12 +51,12 @@ struct kvm_steal_time {
>>  };
>>  
>>  #define KVM_CLOCK_PAIRING_WALLCLOCK 0
>> -struct kvm_clock_offset {
>> +struct kvm_clock_pairing {
>>  	__s64 sec;
>>  	__s64 nsec;
>>  	__u64 tsc;
>>  	__u32 flags;
>> -	__u32 pad[9];
>> +	__u32 pad[1];
>>  };
>>  
>>  #define KVM_STEAL_ALIGNMENT_BITS 5
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 4ecc3145ea4b..09e5d31dac98 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -6149,9 +6149,9 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
>>  EXPORT_SYMBOL_GPL(kvm_emulate_halt);
>>  
>>  static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
>> -			       unsigned long clock_type)
>> +			        unsigned long clock_type)
>>  {
>> -	struct kvm_clock_offset *clock_offset;
>> +	struct kvm_clock_pairing clock_pairing;
>>  	struct timespec ts;
>>  	cycle_t cycle;
>>  	int ret;
>> @@ -6159,30 +6159,19 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
>>  	if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
>>  		return -KVM_EOPNOTSUPP;
>>  
>> -	if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
>> -		return -KVM_EOPNOTSUPP;
>> -
>> -	clock_offset = kzalloc(sizeof(struct kvm_clock_offset), GFP_KERNEL);
>> -	if (clock_offset == NULL)
>> -		return -KVM_ENOMEM;
>> -
>> -	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
>> -		kfree(clock_offset);
>> +	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false)
>>  		return -KVM_EOPNOTSUPP;
>> -	}
>>  
>> -	clock_offset->sec = ts.tv_sec;
>> -	clock_offset->nsec = ts.tv_nsec;
>> -	clock_offset->tsc = kvm_read_l1_tsc(vcpu, cycle);
>> -	clock_offset->flags = 0;
>> +	clock_pairing.sec = ts.tv_sec;
>> +	clock_pairing.nsec = ts.tv_nsec;
>> +	clock_pairing.tsc = kvm_read_l1_tsc(vcpu, cycle);
>> +	clock_pairing.flags = 0;
>>  
>>  	ret = 0;
>> -	if (kvm_write_guest(vcpu->kvm, paddr, clock_offset,
>> -			      sizeof(struct kvm_clock_offset)))
>> +	if (kvm_write_guest(vcpu->kvm, paddr, &clock_pairing,
>> +			    sizeof(struct kvm_clock_pairing)))
>>  		ret = -KVM_EFAULT;
>>  
>> -	kfree(clock_offset);
>> -
>>  	return ret;
>>  }
>>  
>> diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
>> index 68da60e7f519..c72128527377 100644
>> --- a/include/uapi/linux/kvm_para.h
>> +++ b/include/uapi/linux/kvm_para.h
>> @@ -14,7 +14,7 @@
>>  #define KVM_EFAULT		EFAULT
>>  #define KVM_E2BIG		E2BIG
>>  #define KVM_EPERM		EPERM
>> -#define KVM_EOPNOTSUPP		EOPNOTSUPP
>> +#define KVM_EOPNOTSUPP		95
>>  #define KVM_ENOMEM		ENOMEM
>>  
>>  #define KVM_HC_VAPIC_POLL_IRQ		1
>>
>> Okay?
> 
> Just not the padding please, the rest is fine.
> 
>>
>> Paolo
>>
>>>  #define KVM_HC_VAPIC_POLL_IRQ		1
>>>  #define KVM_HC_MMU_OP			2
>>> @@ -23,6 +25,7 @@
>>>  #define KVM_HC_MIPS_GET_CLOCK_FREQ	6
>>>  #define KVM_HC_MIPS_EXIT_VM		7
>>>  #define KVM_HC_MIPS_CONSOLE_OUTPUT	8
>>> +#define KVM_HC_CLOCK_PAIRING		9
>>>  
>>>  /*
>>>   * hypercalls use architecture specific
>>>
>>>
>>>

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#1566573

FromMarcelo Tosatti <mtosatti@redhat.com>
Date2017-01-25 14:10 +0100
Message-ID<t3vuO-2ag-9@gated-at.bofh.it>
In reply to#1566570
On Wed, Jan 25, 2017 at 01:59:34PM +0100, Paolo Bonzini wrote:
> 
> 
> On 25/01/2017 13:55, Marcelo Tosatti wrote:
> > On Wed, Jan 25, 2017 at 01:30:49PM +0100, Paolo Bonzini wrote:
> >>
> >>
> >> On 24/01/2017 18:09, Marcelo Tosatti wrote:
> >>> Add a hypercall to retrieve the host realtime clock
> >>> and the TSC value used to calculate that clock read.
> >>>
> >>> Used to implement clock synchronization between
> >>> host and guest.
> >>>
> >>> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> >>>
> >>> ---
> >>>  Documentation/virtual/kvm/hypercalls.txt |   33 ++++++++++++++++++++++++
> >>>  arch/x86/include/uapi/asm/kvm_para.h     |    9 ++++++
> >>>  arch/x86/kvm/x86.c                       |   41 +++++++++++++++++++++++++++++++
> >>>  include/uapi/linux/kvm_para.h            |    3 ++
> >>>  4 files changed, 86 insertions(+)
> >>>
> >>> v2: improve documentation (Radim)
> >>>     change hypercall name to KVM_HC_CLOCK_PAIRING (Radim)
> >>>     increase padding size
> >>>
> >>> Index: kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h
> >>> ===================================================================
> >>> --- kvm-ptpdriver.orig/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
> >>> +++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:25.038258187 -0200
> >>> @@ -50,6 +50,15 @@
> >>>  	__u32 pad[11];
> >>>  };
> >>>  
> >>> +#define KVM_CLOCK_PAIRING_WALLCLOCK 0
> >>> +struct kvm_clock_offset {
> >>
> >> The struct still has the old name.
> >>
> >>> +	__s64 sec;
> >>> +	__s64 nsec;
> >>> +	__u64 tsc;
> >>> +	__u32 flags;
> >>> +	__u32 pad[9];
> >>> +};
> > 
> > That was on purpose: "to pair" is the operation. 
> > 
> > "struct kvm_clock_pairing" makes no sense to me 
> > (because pairing is an "action").
> > 
> > (if you'd prefer that name, let me know).
> 
> A "pairing" is a union of two things, in this case a sec/nsec value and
> a TSC value.  (I had to look it up in the dictionary though :)).
> 
> >>>  #define KVM_STEAL_ALIGNMENT_BITS 5
> >>>  #define KVM_STEAL_VALID_BITS ((-1ULL << (KVM_STEAL_ALIGNMENT_BITS + 1)))
> >>>  #define KVM_STEAL_RESERVED_MASK (((1 << KVM_STEAL_ALIGNMENT_BITS) - 1 ) << 1)
> >>> Index: kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt
> >>> ===================================================================
> >>> --- kvm-ptpdriver.orig/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:11.947240575 -0200
> >>> +++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:25.038258187 -0200
> >>> @@ -81,3 +81,36 @@
> >>>  same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
> >>>  specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
> >>>  is used in the hypercall for future use.
> >>> +
> >>> +
> >>> +6. KVM_HC_CLOCK_PAIRING
> >>> +------------------------
> >>> +Architecture: x86
> >>> +Status: active
> >>> +Purpose: Hypercall used to synchronize host and guest clocks.
> >>> +Usage:
> >>> +
> >>> +a0: guest physical address where host copies
> >>> +"struct kvm_clock_offset" structure.
> >>> +
> >>> +a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
> >>> +is supported (hosts CLOCK_REALTIME clock).
> >>> +
> >>> +		struct kvm_clock_offset {
> >>
> >> Name of the struct not adjusted.
> >>> +			__s64 sec;
> >>> +			__s64 nsec;
> >>> +			__u64 tsc;
> >>> +			__u32 flags;
> >>> +			__u32 pad[9];
> >>
> >> I'd just leave one element of padding and put the struct on the stack, 
> >> since we have no reason to think we'll need a lot of padding.
> > 
> > Well you don't know: we could implement it in case of HPET clocksource
> > hosts.
> 
> But then the guest wouldn't have a TSC value to use, would it?
> 
> Also, how would it use more padding?

I don't know, maybe pass the TSC and host HPET read in the structure? 
(after exposing the HPET to the guest).

Or maybe you want to sync CLOCK_MONOTONIC and that requires other data.

Not sure.

Just some space if new features are necessary.

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#1566580

FromPaolo Bonzini <pbonzini@redhat.com>
Date2017-01-25 14:20 +0100
Message-ID<t3vEu-2eb-11@gated-at.bofh.it>
In reply to#1566573

On 25/01/2017 14:06, Marcelo Tosatti wrote:
>>> Well you don't know: we could implement it in case of HPET clocksource
>>> hosts.
>> But then the guest wouldn't have a TSC value to use, would it?
>>
>> Also, how would it use more padding?
> I don't know, maybe pass the TSC and host HPET read in the structure? 
> (after exposing the HPET to the guest).
> 
> Or maybe you want to sync CLOCK_MONOTONIC and that requires other data.
> 
> Not sure.
> 
> Just some space if new features are necessary.

Fair enough.

Paolo

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#1566571

FromMarcelo Tosatti <mtosatti@redhat.com>
Date2017-01-25 14:00 +0100
Message-ID<t3vl9-1RZ-35@gated-at.bofh.it>
In reply to#1566561
On Wed, Jan 25, 2017 at 01:30:49PM +0100, Paolo Bonzini wrote:
> 
> 
> On 24/01/2017 18:09, Marcelo Tosatti wrote:
> > Add a hypercall to retrieve the host realtime clock
> > and the TSC value used to calculate that clock read.
> > 
> > Used to implement clock synchronization between
> > host and guest.
> > 
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> > 
> > ---
> >  Documentation/virtual/kvm/hypercalls.txt |   33 ++++++++++++++++++++++++
> >  arch/x86/include/uapi/asm/kvm_para.h     |    9 ++++++
> >  arch/x86/kvm/x86.c                       |   41 +++++++++++++++++++++++++++++++
> >  include/uapi/linux/kvm_para.h            |    3 ++
> >  4 files changed, 86 insertions(+)
> > 
> > v2: improve documentation (Radim)
> >     change hypercall name to KVM_HC_CLOCK_PAIRING (Radim)
> >     increase padding size
> > 
> > Index: kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h
> > ===================================================================
> > --- kvm-ptpdriver.orig/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
> > +++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 16:43:25.038258187 -0200
> > @@ -50,6 +50,15 @@
> >  	__u32 pad[11];
> >  };
> >  
> > +#define KVM_CLOCK_PAIRING_WALLCLOCK 0
> > +struct kvm_clock_offset {
> 
> The struct still has the old name.
> 
> > +	__s64 sec;
> > +	__s64 nsec;
> > +	__u64 tsc;
> > +	__u32 flags;
> > +	__u32 pad[9];
> > +};

That was on purpose: "to pair" is the operation. 

"struct kvm_clock_pairing" makes no sense to me 
(because pairing is an "action").

(if you'd prefer that name, let me know).

> >  #define KVM_STEAL_ALIGNMENT_BITS 5
> >  #define KVM_STEAL_VALID_BITS ((-1ULL << (KVM_STEAL_ALIGNMENT_BITS + 1)))
> >  #define KVM_STEAL_RESERVED_MASK (((1 << KVM_STEAL_ALIGNMENT_BITS) - 1 ) << 1)
> > Index: kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt
> > ===================================================================
> > --- kvm-ptpdriver.orig/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:11.947240575 -0200
> > +++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 16:43:25.038258187 -0200
> > @@ -81,3 +81,36 @@
> >  same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
> >  specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
> >  is used in the hypercall for future use.
> > +
> > +
> > +6. KVM_HC_CLOCK_PAIRING
> > +------------------------
> > +Architecture: x86
> > +Status: active
> > +Purpose: Hypercall used to synchronize host and guest clocks.
> > +Usage:
> > +
> > +a0: guest physical address where host copies
> > +"struct kvm_clock_offset" structure.
> > +
> > +a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
> > +is supported (hosts CLOCK_REALTIME clock).
> > +
> > +		struct kvm_clock_offset {
> 
> Name of the struct not adjusted.
> > +			__s64 sec;
> > +			__s64 nsec;
> > +			__u64 tsc;
> > +			__u32 flags;
> > +			__u32 pad[9];
> 
> I'd just leave one element of padding and put the struct on the stack, 
> since we have no reason to think we'll need a lot of padding.

Well you don't know: we could implement it in case of HPET clocksource
hosts.

> > +		};
> > +
> > +       Where:
> > +               * sec: seconds from clock_type clock.
> > +               * nsec: nanoseconds from clock_type clock.
> > +               * tsc: TSC value used to calculate sec/nsec pair
> > +                 (this hypercall only works when host uses TSC clocksource).
> 
> This is already mentioned below, and it's not clear that tsc is a guest 
> TSC value.

Ok fixed.

> > +               * flags: flags, unused (0) at the moment.
> > +
> > +Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
> > +or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
> > +
> > Index: kvm-ptpdriver/arch/x86/kvm/x86.c
> > ===================================================================
> > --- kvm-ptpdriver.orig/arch/x86/kvm/x86.c	2017-01-13 16:43:20.898252596 -0200
> > +++ kvm-ptpdriver/arch/x86/kvm/x86.c	2017-01-13 16:43:25.041258191 -0200
> > @@ -6119,6 +6119,44 @@
> >  }
> >  EXPORT_SYMBOL_GPL(kvm_emulate_halt);
> >  
> > +static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
> > +			       unsigned long clock_type)
> > +{
> > +	struct kvm_clock_offset *clock_offset;
> > +	struct timespec ts;
> > +	cycle_t cycle;
> > +	int ret;
> > +
> > +	if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
> > +		return -KVM_EOPNOTSUPP;
> > +
> > +	if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
> > +		return -KVM_EOPNOTSUPP;
> 
> Already checked in kvm_get_walltime_and_clockread.

Fixed.

> > +	clock_offset = kzalloc(sizeof(struct kvm_clock_offset), GFP_KERNEL);
> > +	if (clock_offset == NULL)
> > +		return -KVM_ENOMEM;
> > +
> > +	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
> > +		kfree(clock_offset);
> > +		return -KVM_EOPNOTSUPP;
> > +	}
> > +	clock_offset->sec = ts.tv_sec;
> > +	clock_offset->nsec = ts.tv_nsec;
> > +	clock_offset->tsc = kvm_read_l1_tsc(vcpu, cycle);
> > +	clock_offset->flags = 0;
> > +
> > +	ret = 0;
> > +	if (kvm_write_guest(vcpu->kvm, paddr, clock_offset,
> > +			      sizeof(struct kvm_clock_offset)))
> > +		ret = -KVM_EFAULT;
> > +
> > +	kfree(clock_offset);
> > +
> > +	return ret;
> > +}
> > +
> >  /*
> >   * kvm_pv_kick_cpu_op:  Kick a vcpu.
> >   *
> > @@ -6183,6 +6221,9 @@
> >  		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
> >  		ret = 0;
> >  		break;
> > +	case KVM_HC_CLOCK_PAIRING:
> > +		ret = kvm_pv_clock_pairing(vcpu, a0, a1);
> > +		break;
> >  	default:
> >  		ret = -KVM_ENOSYS;
> >  		break;
> > Index: kvm-ptpdriver/include/uapi/linux/kvm_para.h
> > ===================================================================
> > --- kvm-ptpdriver.orig/include/uapi/linux/kvm_para.h	2017-01-13 16:43:11.947240575 -0200
> > +++ kvm-ptpdriver/include/uapi/linux/kvm_para.h	2017-01-13 16:43:25.042258192 -0200
> > @@ -14,6 +14,8 @@
> >  #define KVM_EFAULT		EFAULT
> >  #define KVM_E2BIG		E2BIG
> >  #define KVM_EPERM		EPERM
> > +#define KVM_EOPNOTSUPP		EOPNOTSUPP
> > +#define KVM_ENOMEM		ENOMEM
> 
> This file could potentially be used across multiple architectures (it's 
> not in arch/x86/include/uapi/asm), but EOPNOTSUPP is not the same on 
> all systems.  Better use "95" which is the value it has on x86.

Fixed.

> All this gives:
> 
> diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
> index 55eb3e1ca494..cd35de84999f 100644
> --- a/Documentation/virtual/kvm/hypercalls.txt
> +++ b/Documentation/virtual/kvm/hypercalls.txt
> @@ -94,9 +94,9 @@ a0: guest physical address where host copies
>  "struct kvm_clock_offset" structure.
>  
>  a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
> -is supported (hosts CLOCK_REALTIME clock).
> +is supported (corresponding to the host's CLOCK_REALTIME clock).
>  
> -		struct kvm_clock_offset {
> +		struct kvm_clock_pairing {
>  			__s64 sec;
>  			__s64 nsec;
>  			__u64 tsc;
> @@ -107,10 +107,12 @@ is supported (hosts CLOCK_REALTIME clock).
>         Where:
>                 * sec: seconds from clock_type clock.
>                 * nsec: nanoseconds from clock_type clock.
> -               * tsc: TSC value used to calculate sec/nsec pair
> -                 (this hypercall only works when host uses TSC clocksource).
> +               * tsc: guest TSC value used to calculate sec/nsec pair
>                 * flags: flags, unused (0) at the moment.
>  
> +The hypercall lets a guest compute a precise timestamp across
> +host and guest.  The guest can use the returned TSC value to
> +compute the CLOCK_REALTIME for its clock, at the same instant.
> +
>  Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
>  or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
> -
> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
> index ce7b411e28bc..3641d8b7dba9 100644
> --- a/arch/x86/include/uapi/asm/kvm_para.h
> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> @@ -51,12 +51,12 @@ struct kvm_steal_time {
>  };
>  
>  #define KVM_CLOCK_PAIRING_WALLCLOCK 0
> -struct kvm_clock_offset {
> +struct kvm_clock_pairing {
>  	__s64 sec;
>  	__s64 nsec;
>  	__u64 tsc;
>  	__u32 flags;
> -	__u32 pad[9];
> +	__u32 pad[1];
>  };
>  
>  #define KVM_STEAL_ALIGNMENT_BITS 5
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4ecc3145ea4b..09e5d31dac98 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6149,9 +6149,9 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
>  EXPORT_SYMBOL_GPL(kvm_emulate_halt);
>  
>  static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
> -			       unsigned long clock_type)
> +			        unsigned long clock_type)
>  {
> -	struct kvm_clock_offset *clock_offset;
> +	struct kvm_clock_pairing clock_pairing;
>  	struct timespec ts;
>  	cycle_t cycle;
>  	int ret;
> @@ -6159,30 +6159,19 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
>  	if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
>  		return -KVM_EOPNOTSUPP;
>  
> -	if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
> -		return -KVM_EOPNOTSUPP;
> -
> -	clock_offset = kzalloc(sizeof(struct kvm_clock_offset), GFP_KERNEL);
> -	if (clock_offset == NULL)
> -		return -KVM_ENOMEM;
> -
> -	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
> -		kfree(clock_offset);
> +	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false)
>  		return -KVM_EOPNOTSUPP;
> -	}
>  
> -	clock_offset->sec = ts.tv_sec;
> -	clock_offset->nsec = ts.tv_nsec;
> -	clock_offset->tsc = kvm_read_l1_tsc(vcpu, cycle);
> -	clock_offset->flags = 0;
> +	clock_pairing.sec = ts.tv_sec;
> +	clock_pairing.nsec = ts.tv_nsec;
> +	clock_pairing.tsc = kvm_read_l1_tsc(vcpu, cycle);
> +	clock_pairing.flags = 0;
>  
>  	ret = 0;
> -	if (kvm_write_guest(vcpu->kvm, paddr, clock_offset,
> -			      sizeof(struct kvm_clock_offset)))
> +	if (kvm_write_guest(vcpu->kvm, paddr, &clock_pairing,
> +			    sizeof(struct kvm_clock_pairing)))
>  		ret = -KVM_EFAULT;
>  
> -	kfree(clock_offset);
> -
>  	return ret;
>  }
>  
> diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
> index 68da60e7f519..c72128527377 100644
> --- a/include/uapi/linux/kvm_para.h
> +++ b/include/uapi/linux/kvm_para.h
> @@ -14,7 +14,7 @@
>  #define KVM_EFAULT		EFAULT
>  #define KVM_E2BIG		E2BIG
>  #define KVM_EPERM		EPERM
> -#define KVM_EOPNOTSUPP		EOPNOTSUPP
> +#define KVM_EOPNOTSUPP		95
>  #define KVM_ENOMEM		ENOMEM
>  
>  #define KVM_HC_VAPIC_POLL_IRQ		1
> 
> Okay?

Just not the padding please, the rest is fine.

> 
> Paolo
> 
> >  #define KVM_HC_VAPIC_POLL_IRQ		1
> >  #define KVM_HC_MMU_OP			2
> > @@ -23,6 +25,7 @@
> >  #define KVM_HC_MIPS_GET_CLOCK_FREQ	6
> >  #define KVM_HC_MIPS_EXIT_VM		7
> >  #define KVM_HC_MIPS_CONSOLE_OUTPUT	8
> > +#define KVM_HC_CLOCK_PAIRING		9
> >  
> >  /*
> >   * hypercalls use architecture specific
> > 
> > 
> >

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