KVM: x86: add KVM_HC_CLOCK_PAIRING hypercall

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.

Marcelo Tosatti committed 9 years ago

Commit 55dd00a1 parent 6342c504 files · +112 −0Browse files

Unified · Split

4 files

Documentation/virtual/kvm/hypercalls.txt +35 −0
arch/x86/include/uapi/asm/kvm_para.h +9 −0
arch/x86/kvm/x86.c +66 −0
include/uapi/linux/kvm_para.h +2 −0

Documentation/virtual/kvm/hypercalls.txt+35−0

@@ -81,3 +81,38 @@ the vcpu to sleep until occurrence of an appropriate event. Another vcpu of the · 80 unmodified lines
81	same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,	81	same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
82	specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)	82	specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
83	is used in the hypercall for future use.	83	is used in the hypercall for future use.
		84
		85
		86	6. KVM_HC_CLOCK_PAIRING
		87	------------------------
		88	Architecture: x86
		89	Status: active
		90	Purpose: Hypercall used to synchronize host and guest clocks.
		91	Usage:
		92
		93	a0: guest physical address where host copies
		94	"struct kvm_clock_offset" structure.
		95
		96	a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
		97	is supported (corresponding to the host's CLOCK_REALTIME clock).
		98
		99	struct kvm_clock_pairing {
		100	__s64 sec;
		101	__s64 nsec;
		102	__u64 tsc;
		103	__u32 flags;
		104	__u32 pad[9];
		105	};
		106
		107	Where:
		108	* sec: seconds from clock_type clock.
		109	* nsec: nanoseconds from clock_type clock.
		110	* tsc: guest TSC value used to calculate sec/nsec pair
		111	* flags: flags, unused (0) at the moment.
		112
		113	The hypercall lets a guest compute a precise timestamp across
		114	host and guest. The guest can use the returned TSC value to
		115	compute the CLOCK_REALTIME for its clock, at the same instant.
		116
		117	Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
		118	or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.

arch/x86/include/uapi/asm/kvm_para.h+9−0

@@ -50,6 +50,15 @@ struct kvm_steal_time { · 49 unmodified lines
50	__u32 pad[11];	50	__u32 pad[11];
51	};	51	};
52		52
		53	#define KVM_CLOCK_PAIRING_WALLCLOCK 0
		54	struct kvm_clock_pairing {
		55	__s64 sec;
		56	__s64 nsec;
		57	__u64 tsc;
		58	__u32 flags;
		59	__u32 pad[9];
		60	};
		61
53	#define KVM_STEAL_ALIGNMENT_BITS 5	62	#define KVM_STEAL_ALIGNMENT_BITS 5
54	#define KVM_STEAL_VALID_BITS ((-1ULL << (KVM_STEAL_ALIGNMENT_BITS + 1)))	63	#define KVM_STEAL_VALID_BITS ((-1ULL << (KVM_STEAL_ALIGNMENT_BITS + 1)))
55	#define KVM_STEAL_RESERVED_MASK (((1 << KVM_STEAL_ALIGNMENT_BITS) - 1 ) << 1)	64	#define KVM_STEAL_RESERVED_MASK (((1 << KVM_STEAL_ALIGNMENT_BITS) - 1 ) << 1)

arch/x86/kvm/x86.c+66−0

@@ -1142,6 +1142,7 @@ struct pvclock_gtod_data { · 1141 unmodified lines
1142		1142
1143	u64 boot_ns;	1143	u64 boot_ns;
1144	u64 nsec_base;	1144	u64 nsec_base;
		1145	u64 wall_time_sec;
1145	};	1146	};
1146		1147
1147	static struct pvclock_gtod_data pvclock_gtod_data;	1148	static struct pvclock_gtod_data pvclock_gtod_data;
@@ -1165,6 +1166,8 @@ static void update_pvclock_gtod(struct timekeeper *tk) · 17 unmodified lines
1165	vdata->boot_ns = boot_ns;	1166	vdata->boot_ns = boot_ns;
1166	vdata->nsec_base = tk->tkr_mono.xtime_nsec;	1167	vdata->nsec_base = tk->tkr_mono.xtime_nsec;
1167		1168
		1169	vdata->wall_time_sec = tk->xtime_sec;
		1170
1168	write_seqcount_end(&vdata->seq);	1171	write_seqcount_end(&vdata->seq);
1169	}	1172	}
1170	#endif	1173	#endif
@@ -1626,6 +1629,28 @@ static int do_monotonic_boot(s64 t, u64 cycle_now) · 455 unmodified lines
1626	return mode;	1629	return mode;
1627	}	1630	}
1628		1631
		1632	static int do_realtime(struct timespec ts, u64 cycle_now)
		1633	{
		1634	struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
		1635	unsigned long seq;
		1636	int mode;
		1637	u64 ns;
		1638
		1639	do {
		1640	seq = read_seqcount_begin(&gtod->seq);
		1641	mode = gtod->clock.vclock_mode;
		1642	ts->tv_sec = gtod->wall_time_sec;
		1643	ns = gtod->nsec_base;
		1644	ns += vgettsc(cycle_now);
		1645	ns >>= gtod->clock.shift;
		1646	} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
		1647
		1648	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
		1649	ts->tv_nsec = ns;
		1650
		1651	return mode;
		1652	}
		1653
1629	/* returns true if host is using tsc clocksource */	1654	/* returns true if host is using tsc clocksource */
1630	static bool kvm_get_time_and_clockread(s64 kernel_ns, u64 cycle_now)	1655	static bool kvm_get_time_and_clockread(s64 kernel_ns, u64 cycle_now)
1631	{	1656	{
@@ -1635,6 +1660,17 @@ static bool kvm_get_time_and_clockread(s64 kernel_ns, u64 cycle_now) · 3 unmodified lines
1635		1660
1636	return do_monotonic_boot(kernel_ns, cycle_now) == VCLOCK_TSC;	1661	return do_monotonic_boot(kernel_ns, cycle_now) == VCLOCK_TSC;
1637	}	1662	}
		1663
		1664	/* returns true if host is using tsc clocksource */
		1665	static bool kvm_get_walltime_and_clockread(struct timespec *ts,
		1666	u64 *cycle_now)
		1667	{
		1668	/* checked again under seqlock below */
		1669	if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
		1670	return false;
		1671
		1672	return do_realtime(ts, cycle_now) == VCLOCK_TSC;
		1673	}
1638	#endif	1674	#endif
1639		1675
1640	/*	1676	/*
@@ -6112,6 +6148,33 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu) · 4471 unmodified lines
6112	}	6148	}
6113	EXPORT_SYMBOL_GPL(kvm_emulate_halt);	6149	EXPORT_SYMBOL_GPL(kvm_emulate_halt);
6114		6150
		6151	static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
		6152	unsigned long clock_type)
		6153	{
		6154	struct kvm_clock_pairing clock_pairing;
		6155	struct timespec ts;
		6156	cycle_t cycle;
		6157	int ret;
		6158
		6159	if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
		6160	return -KVM_EOPNOTSUPP;
		6161
		6162	if (kvm_get_walltime_and_clockread(&ts, &cycle) == false)
		6163	return -KVM_EOPNOTSUPP;
		6164
		6165	clock_pairing.sec = ts.tv_sec;
		6166	clock_pairing.nsec = ts.tv_nsec;
		6167	clock_pairing.tsc = kvm_read_l1_tsc(vcpu, cycle);
		6168	clock_pairing.flags = 0;
		6169
		6170	ret = 0;
		6171	if (kvm_write_guest(vcpu->kvm, paddr, &clock_pairing,
		6172	sizeof(struct kvm_clock_pairing)))
		6173	ret = -KVM_EFAULT;
		6174
		6175	return ret;
		6176	}
		6177
6115	/*	6178	/*
6116	* kvm_pv_kick_cpu_op: Kick a vcpu.	6179	* kvm_pv_kick_cpu_op: Kick a vcpu.
6117	*	6180	*
@@ -6176,6 +6239,9 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) · 58 unmodified lines
6176	kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);	6239	kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
6177	ret = 0;	6240	ret = 0;
6178	break;	6241	break;
		6242	case KVM_HC_CLOCK_PAIRING:
		6243	ret = kvm_pv_clock_pairing(vcpu, a0, a1);
		6244	break;
6179	default:	6245	default:
6180	ret = -KVM_ENOSYS;	6246	ret = -KVM_ENOSYS;
6181	break;	6247	break;

include/uapi/linux/kvm_para.h+2−0

 #define KVM_EFAULT		EFAULT
 #define KVM_E2BIG		E2BIG
 #define KVM_EPERM		EPERM
+#define KVM_EOPNOTSUPP		95
 #define KVM_HC_VAPIC_POLL_IRQ		1
 #define KVM_HC_MMU_OP			2
 #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

KVM: x86: add KVM_HC_CLOCK_PAIRING hypercall

Keyboard shortcuts

General

Issues and pull requests

Issues, pull requests and Inbox

Repository code