Commit 55dd00a7 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Paolo Bonzini

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.
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 6342c50a
......@@ -81,3 +81,38 @@ the vcpu to sleep until occurrence of an appropriate event. Another vcpu of the
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 (corresponding to the host's CLOCK_REALTIME clock).
struct kvm_clock_pairing {
__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: 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.
......@@ -50,6 +50,15 @@ struct kvm_steal_time {
__u32 pad[11];
};
#define KVM_CLOCK_PAIRING_WALLCLOCK 0
struct kvm_clock_pairing {
__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)
......
......@@ -1142,6 +1142,7 @@ struct pvclock_gtod_data {
u64 boot_ns;
u64 nsec_base;
u64 wall_time_sec;
};
static struct pvclock_gtod_data pvclock_gtod_data;
......@@ -1165,6 +1166,8 @@ static void update_pvclock_gtod(struct timekeeper *tk)
vdata->boot_ns = boot_ns;
vdata->nsec_base = tk->tkr_mono.xtime_nsec;
vdata->wall_time_sec = tk->xtime_sec;
write_seqcount_end(&vdata->seq);
}
#endif
......@@ -1626,6 +1629,28 @@ static int do_monotonic_boot(s64 *t, u64 *cycle_now)
return mode;
}
static int do_realtime(struct timespec *ts, u64 *cycle_now)
{
struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
unsigned long seq;
int mode;
u64 ns;
do {
seq = read_seqcount_begin(&gtod->seq);
mode = gtod->clock.vclock_mode;
ts->tv_sec = gtod->wall_time_sec;
ns = gtod->nsec_base;
ns += vgettsc(cycle_now);
ns >>= gtod->clock.shift;
} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
ts->tv_nsec = ns;
return mode;
}
/* returns true if host is using tsc clocksource */
static bool kvm_get_time_and_clockread(s64 *kernel_ns, u64 *cycle_now)
{
......@@ -1635,6 +1660,17 @@ static bool kvm_get_time_and_clockread(s64 *kernel_ns, u64 *cycle_now)
return do_monotonic_boot(kernel_ns, cycle_now) == VCLOCK_TSC;
}
/* returns true if host is using tsc clocksource */
static bool kvm_get_walltime_and_clockread(struct timespec *ts,
u64 *cycle_now)
{
/* checked again under seqlock below */
if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
return false;
return do_realtime(ts, cycle_now) == VCLOCK_TSC;
}
#endif
/*
......@@ -6112,6 +6148,33 @@ 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)
{
struct kvm_clock_pairing clock_pairing;
struct timespec ts;
cycle_t cycle;
int ret;
if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
return -KVM_EOPNOTSUPP;
if (kvm_get_walltime_and_clockread(&ts, &cycle) == false)
return -KVM_EOPNOTSUPP;
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_pairing,
sizeof(struct kvm_clock_pairing)))
ret = -KVM_EFAULT;
return ret;
}
/*
* kvm_pv_kick_cpu_op: Kick a vcpu.
*
......@@ -6176,6 +6239,9 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
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;
......
......@@ -14,6 +14,7 @@
#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
......@@ -23,6 +24,7 @@
#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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