diff mbox

[2/3] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall

Message ID 20170113120319.692007194@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Marcelo Tosatti Jan. 13, 2017, 12:01 p.m. UTC 
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 |   30 ++++++++++++++++++++++
 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, 83 insertions(+)



--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Comments

Radim Krčmář Jan. 13, 2017, 3:31 p.m. UTC | #1 
2017-01-13 10:01-0200, Marcelo Tosatti:
> 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 |   30 ++++++++++++++++++++++
>  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, 83 insertions(+)
> 
> 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 09:03:33.823305270 -0200
> +++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 09:07:54.633699270 -0200
> @@ -50,6 +50,15 @@
>  	__u32 pad[11];
>  };
>  
> +#define KVM_CLOCK_OFFSET_WALLCLOCK 0
> +struct kvm_clock_offset {
> +	__s64 sec;
> +	__s64 nsec;
> +	__u64 tsc;
> +	__u32 flags;
> +	__u32 pad[1];
> +};
> +
>  #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 09:03:33.823305270 -0200
> +++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 09:15:32.971389949 -0200
> @@ -81,3 +81,33 @@
>  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_OFFSET
> +------------------------
> +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_OFFSET_WALLCLOCK (0)
> +is supported (hosts CLOCK_REALTIME clock).
> +
> +		struct kvm_clock_offset {
> +			__s64 sec;
> +			__s64 nsec;

Why is nsec:
 1) signed -- it is a remainder after division by NSEC_PER_SEC
 2) bigger than 32 bit -- NSEC_PER_SEC < 2^32
?

> +			__u64 tsc;
> +			__u32 flags;
> +			__u32 pad;
> +		};
> +
> +       Where:
> +               * sec: seconds from clock_type clock.
> +               * nsec: nanoseconds from clock_type clock.

The important part of an offset is the starting point -- I assume it is
the the usual one, but documentation better be explicit.

> +               * tsc: TSC value used to calculate sec/nsec pair

This hypercall could in theory work even when computing the offset with
a different clocksource on the host and the estimating TSC at that time.

> +                 (this hypercall only works when host uses TSC clocksource).

Describe that error as a return value.

> +               * flags: flags, unused at the moment.

unused = 0.

> +
> Index: kvm-ptpdriver/arch/x86/kvm/x86.c
> ===================================================================
> --- kvm-ptpdriver.orig/arch/x86/kvm/x86.c	2017-01-13 09:04:46.581415259 -0200
> +++ kvm-ptpdriver/arch/x86/kvm/x86.c	2017-01-13 09:08:51.557785166 -0200
> @@ -6121,6 +6121,44 @@
>  }
>  EXPORT_SYMBOL_GPL(kvm_emulate_halt);
>  
> +static int kvm_pv_clock_offset(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_OFFSET_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);

Can't clock_offset be on the stack?

> +	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.
>   *
> @@ -6185,6 +6223,9 @@
>  		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
>  		ret = 0;
>  		break;
> +	case KVM_HC_CLOCK_OFFSET:
> +		ret = kvm_pv_clock_offset(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 09:03:33.823305270 -0200
> +++ kvm-ptpdriver/include/uapi/linux/kvm_para.h	2017-01-13 09:07:54.636699274 -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_OFFSET		9
>  
>  /*
>   * hypercalls use architecture specific
> 
> 
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Marcelo Tosatti Jan. 13, 2017, 3:43 p.m. UTC | #2 
On Fri, Jan 13, 2017 at 04:31:58PM +0100, Radim Krcmar wrote:
> 2017-01-13 10:01-0200, Marcelo Tosatti:
> > 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 |   30 ++++++++++++++++++++++
> >  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, 83 insertions(+)
> > 
> > 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 09:03:33.823305270 -0200
> > +++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 09:07:54.633699270 -0200
> > @@ -50,6 +50,15 @@
> >  	__u32 pad[11];
> >  };
> >  
> > +#define KVM_CLOCK_OFFSET_WALLCLOCK 0
> > +struct kvm_clock_offset {
> > +	__s64 sec;
> > +	__s64 nsec;
> > +	__u64 tsc;
> > +	__u32 flags;
> > +	__u32 pad[1];
> > +};
> > +
> >  #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 09:03:33.823305270 -0200
> > +++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 09:15:32.971389949 -0200
> > @@ -81,3 +81,33 @@
> >  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_OFFSET
> > +------------------------
> > +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_OFFSET_WALLCLOCK (0)
> > +is supported (hosts CLOCK_REALTIME clock).
> > +
> > +		struct kvm_clock_offset {
> > +			__s64 sec;
> > +			__s64 nsec;
> 
> Why is nsec:
>  1) signed -- it is a remainder after division by NSEC_PER_SEC

Because "struct timespec" is signed because it can be used for
time deltas (you won't actually get signed values for
kvm_get_walltime_and_clockread).

Just wanted to match "struct timespec".

>  2) bigger than 32 bit -- NSEC_PER_SEC < 2^32
> ?

Again matching struct timespec.

> > +			__u64 tsc;
> > +			__u32 flags;
> > +			__u32 pad;
> > +		};
> > +
> > +       Where:
> > +               * sec: seconds from clock_type clock.
> > +               * nsec: nanoseconds from clock_type clock.
> 
> The important part of an offset is the starting point -- I assume it is
> the the usual one, but documentation better be explicit.

Don't get what you mean? (the values have same meaning as hosts
clock_gettime(CLOCK_REALTIME), supposedly that is clear).

> > +               * tsc: TSC value used to calculate sec/nsec pair
> 
> This hypercall could in theory work even when computing the offset with
> a different clocksource on the host and the estimating TSC at that time.

Yes it could.

> > +                 (this hypercall only works when host uses TSC clocksource).
> 
> Describe that error as a return value.

Fixed.

+
+       if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
+               kfree(clock_offset);
+               return -KVM_EOPNOTSUPP;
+       }

> 
> > +               * flags: flags, unused at the moment.
> 
> unused = 0.

Fixed.

> > +
> > Index: kvm-ptpdriver/arch/x86/kvm/x86.c
> > ===================================================================
> > --- kvm-ptpdriver.orig/arch/x86/kvm/x86.c	2017-01-13 09:04:46.581415259 -0200
> > +++ kvm-ptpdriver/arch/x86/kvm/x86.c	2017-01-13 09:08:51.557785166 -0200
> > @@ -6121,6 +6121,44 @@
> >  }
> >  EXPORT_SYMBOL_GPL(kvm_emulate_halt);
> >  
> > +static int kvm_pv_clock_offset(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_OFFSET_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);
> 
> Can't clock_offset be on the stack?

Well since the kernel stack is limited, thought it would be safer to 
allocate it.

> > +	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.
> >   *
> > @@ -6185,6 +6223,9 @@
> >  		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
> >  		ret = 0;
> >  		break;
> > +	case KVM_HC_CLOCK_OFFSET:
> > +		ret = kvm_pv_clock_offset(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 09:03:33.823305270 -0200
> > +++ kvm-ptpdriver/include/uapi/linux/kvm_para.h	2017-01-13 09:07:54.636699274 -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_OFFSET		9
> >  
> >  /*
> >   * hypercalls use architecture specific
> > 
> > 
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Radim Krčmář Jan. 13, 2017, 5:07 p.m. UTC | #3 
2017-01-13 13:43-0200, Marcelo Tosatti:
> On Fri, Jan 13, 2017 at 04:31:58PM +0100, Radim Krcmar wrote:
>> 2017-01-13 10:01-0200, Marcelo Tosatti:
>> > 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>
>> > 
>> > ---
>> > Index: kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt
>> > @@ -81,3 +81,33 @@
>> > +6. KVM_HC_CLOCK_OFFSET
>> > +------------------------
>> > +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_OFFSET_WALLCLOCK (0)
>> > +is supported (hosts CLOCK_REALTIME clock).
>> > +
>> > +		struct kvm_clock_offset {
>> > +			__s64 sec;
>> > +			__s64 nsec;
>> 
>> Why is nsec:
>>  1) signed -- it is a remainder after division by NSEC_PER_SEC
> 
> Because "struct timespec" is signed because it can be used for
> time deltas (you won't actually get signed values for
> kvm_get_walltime_and_clockread).
> 
> Just wanted to match "struct timespec".
> 
>>  2) bigger than 32 bit -- NSEC_PER_SEC < 2^32
>> ?
> 
> Again matching struct timespec.

It is "long" in struct timespec, which could also be "s32" ...
I'd rather waste those 8 bytes inside padding -- its purpose is clear
there. :)

>> > +			__u64 tsc;
>> > +			__u32 flags;
>> > +			__u32 pad;
>> > +		};
>> > +
>> > +       Where:
>> > +               * sec: seconds from clock_type clock.
>> > +               * nsec: nanoseconds from clock_type clock.
>> 
>> The important part of an offset is the starting point -- I assume it is
>> the the usual one, but documentation better be explicit.
> 
> Don't get what you mean? (the values have same meaning as hosts
> clock_gettime(CLOCK_REALTIME), supposedly that is clear).

Ah, I didn't understand that clock_type was refering to CLOCK_REALTIME.

I'd drop offset from the hypercall name.  IIUC, all various clock types
would be compared to TSC, so we could name the hypercall somewhat like
KVM_HC_CLOCK_AT_TSC -- we want to know what was the time on the selected
clock when TSC was at value __u64 tsc.
The only offset is between sec+nsec and the beginning of time (and tsc
and 0), but we don't care about that offset by itself -- we care about
relation of sec+nsec to tsc, which isn't a simple offset as they flow
differently.

If we wanted to be more generic, then KVM_HC_CLOCK_PAIRING/SNAPSHOT/...
and argument 1 would contain clock_types, here REALTIME and TSC.
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Marcelo Tosatti Jan. 13, 2017, 5:57 p.m. UTC | #4 
On Fri, Jan 13, 2017 at 06:07:40PM +0100, Radim Krcmar wrote:
> 2017-01-13 13:43-0200, Marcelo Tosatti:
> > On Fri, Jan 13, 2017 at 04:31:58PM +0100, Radim Krcmar wrote:
> >> 2017-01-13 10:01-0200, Marcelo Tosatti:
> >> > 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>
> >> > 
> >> > ---
> >> > Index: kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt
> >> > @@ -81,3 +81,33 @@
> >> > +6. KVM_HC_CLOCK_OFFSET
> >> > +------------------------
> >> > +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_OFFSET_WALLCLOCK (0)
> >> > +is supported (hosts CLOCK_REALTIME clock).
> >> > +
> >> > +		struct kvm_clock_offset {
> >> > +			__s64 sec;
> >> > +			__s64 nsec;
> >> 
> >> Why is nsec:
> >>  1) signed -- it is a remainder after division by NSEC_PER_SEC
> > 
> > Because "struct timespec" is signed because it can be used for
> > time deltas (you won't actually get signed values for
> > kvm_get_walltime_and_clockread).
> > 
> > Just wanted to match "struct timespec".
> > 
> >>  2) bigger than 32 bit -- NSEC_PER_SEC < 2^32
> >> ?
> > 
> > Again matching struct timespec.
> 
> It is "long" in struct timespec, which could also be "s32" ...

Which fits in a s64.

> I'd rather waste those 8 bytes inside padding -- its purpose is clear
> there. :)

The purpose of the s64 is to match timespec.

> >> > +			__u64 tsc;
> >> > +			__u32 flags;
> >> > +			__u32 pad;
> >> > +		};
> >> > +
> >> > +       Where:
> >> > +               * sec: seconds from clock_type clock.
> >> > +               * nsec: nanoseconds from clock_type clock.
> >> 
> >> The important part of an offset is the starting point -- I assume it is
> >> the the usual one, but documentation better be explicit.
> > 
> > Don't get what you mean? (the values have same meaning as hosts
> > clock_gettime(CLOCK_REALTIME), supposedly that is clear).
> 
> Ah, I didn't understand that clock_type was refering to CLOCK_REALTIME.
> 
> I'd drop offset from the hypercall name.  IIUC, all various clock types
> would be compared to TSC, so we could name the hypercall somewhat like
> KVM_HC_CLOCK_AT_TSC -- we want to know what was the time on the selected
> clock when TSC was at value __u64 tsc.

Well its the offset from TSC, so thats why "offset" in the name.

And as you say, the interface could be extended to support 
other clocks (using the available data in pad, i'll make it larger BTW).

Which would render the "TSC" from the hypercall name invalid.

> The only offset is between sec+nsec and the beginning of time (and tsc
> and 0), but we don't care about that offset by itself -- we care about
> relation of sec+nsec to tsc, which isn't a simple offset as they flow
> differently.
> 
> If we wanted to be more generic, then KVM_HC_CLOCK_PAIRING/SNAPSHOT/...
> and argument 1 would contain clock_types, here REALTIME and TSC.

Pairing is fine, changed.

--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

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 09:03:33.823305270 -0200
+++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h	2017-01-13 09:07:54.633699270 -0200
@@ -50,6 +50,15 @@ 
 	__u32 pad[11];
 };
 
+#define KVM_CLOCK_OFFSET_WALLCLOCK 0
+struct kvm_clock_offset {
+	__s64 sec;
+	__s64 nsec;
+	__u64 tsc;
+	__u32 flags;
+	__u32 pad[1];
+};
+
 #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 09:03:33.823305270 -0200
+++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt	2017-01-13 09:15:32.971389949 -0200
@@ -81,3 +81,33 @@ 
 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_OFFSET
+------------------------
+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_OFFSET_WALLCLOCK (0)
+is supported (hosts CLOCK_REALTIME clock).
+
+		struct kvm_clock_offset {
+			__s64 sec;
+			__s64 nsec;
+			__u64 tsc;
+			__u32 flags;
+			__u32 pad;
+		};
+
+       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 at the moment.
+
Index: kvm-ptpdriver/arch/x86/kvm/x86.c
===================================================================
--- kvm-ptpdriver.orig/arch/x86/kvm/x86.c	2017-01-13 09:04:46.581415259 -0200
+++ kvm-ptpdriver/arch/x86/kvm/x86.c	2017-01-13 09:08:51.557785166 -0200
@@ -6121,6 +6121,44 @@ 
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_halt);
 
+static int kvm_pv_clock_offset(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_OFFSET_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.
  *
@@ -6185,6 +6223,9 @@ 
 		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
 		ret = 0;
 		break;
+	case KVM_HC_CLOCK_OFFSET:
+		ret = kvm_pv_clock_offset(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 09:03:33.823305270 -0200
+++ kvm-ptpdriver/include/uapi/linux/kvm_para.h	2017-01-13 09:07:54.636699274 -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_OFFSET		9
 
 /*
  * hypercalls use architecture specific