Introduce a function that reads the exact nanoseconds value that is
provided to the guest in kvmclock. This crystallizes the notion of
kvmclock as a thin veneer over a stable TSC, that the guest will
(hopefully) convert with NTP. In other words, kvmclock is *not* a
paravirtualized host-to-guest NTP.
Drop the get_kernel_ns() function, that was used both to get the base
value of the master clock and to get the current value of kvmclock.
The former use is replaced by ktime_get_boot_ns(), the latter is
the purpose of get_kernel_ns().
This also allows KVM to provide a Hyper-V time reference counter that
is synchronized with the time that is computed from the TSC page.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/entry/vdso/vclock_gettime.c | 2 +-
arch/x86/include/asm/pvclock.h | 5 ++--
arch/x86/kernel/pvclock.c | 2 +-
arch/x86/kvm/hyperv.c | 2 +-
arch/x86/kvm/x86.c | 48 +++++++++++++++++++++++++++---------
arch/x86/kvm/x86.h | 6 +----
6 files changed, 43 insertions(+), 22 deletions(-)
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index 94d54d0defa7..02223cb4bcfd 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -129,7 +129,7 @@ static notrace cycle_t vread_pvclock(int *mode)
return 0;
}
- ret = __pvclock_read_cycles(pvti);
+ ret = __pvclock_read_cycles(pvti, rdtsc_ordered());
} while (pvclock_read_retry(pvti, version));
/* refer to vread_tsc() comment for rationale */
diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index d019f0cc80ec..3ad741b84072 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -87,9 +87,10 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
}
static __always_inline
-cycle_t __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src)
+cycle_t __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
+ u64 tsc)
{
- u64 delta = rdtsc_ordered() - src->tsc_timestamp;
+ u64 delta = tsc - src->tsc_timestamp;
cycle_t offset = pvclock_scale_delta(delta, src->tsc_to_system_mul,
src->tsc_shift);
return src->system_time + offset;
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 3599404e3089..5b2cc889ce34 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -80,7 +80,7 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
do {
version = pvclock_read_begin(src);
- ret = __pvclock_read_cycles(src);
+ ret = __pvclock_read_cycles(src, rdtsc_ordered());
flags = src->flags;
} while (pvclock_read_retry(src, version));
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 01bd7b7a6866..ed5b77f39ffb 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -386,7 +386,7 @@ static void synic_init(struct kvm_vcpu_hv_synic *synic)
static u64 get_time_ref_counter(struct kvm *kvm)
{
- return div_u64(get_kernel_ns() + kvm->arch.kvmclock_offset, 100);
+ return div_u64(get_kvmclock_ns(kvm), 100);
}
static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b5853b86b67d..2edcfa054cbe 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1425,7 +1425,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
raw_spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags);
offset = kvm_compute_tsc_offset(vcpu, data);
- ns = get_kernel_ns();
+ ns = ktime_get_boot_ns();
elapsed = ns - kvm->arch.last_tsc_nsec;
if (vcpu->arch.virtual_tsc_khz) {
@@ -1716,6 +1716,34 @@ static void kvm_gen_update_masterclock(struct kvm *kvm)
#endif
}
+static u64 __get_kvmclock_ns(struct kvm *kvm)
+{
+ struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, 0);
+ struct kvm_arch *ka = &kvm->arch;
+ s64 ns;
+
+ if (vcpu->arch.hv_clock.flags & PVCLOCK_TSC_STABLE_BIT) {
+ u64 tsc = kvm_read_l1_tsc(vcpu, rdtsc());
+ ns = __pvclock_read_cycles(&vcpu->arch.hv_clock, tsc);
+ } else {
+ ns = ktime_get_boot_ns() + ka->kvmclock_offset;
+ }
+
+ return ns;
+}
+
+u64 get_kvmclock_ns(struct kvm *kvm)
+{
+ unsigned long flags;
+ s64 ns;
+
+ local_irq_save(flags);
+ ns = __get_kvmclock_ns(kvm);
+ local_irq_restore(flags);
+
+ return ns;
+}
+
static void kvm_setup_pvclock_page(struct kvm_vcpu *v)
{
struct kvm_vcpu_arch *vcpu = &v->arch;
@@ -1805,7 +1833,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
}
if (!use_master_clock) {
host_tsc = rdtsc();
- kernel_ns = get_kernel_ns();
+ kernel_ns = ktime_get_boot_ns();
}
tsc_timestamp = kvm_read_l1_tsc(v, host_tsc);
@@ -4048,7 +4076,6 @@ long kvm_arch_vm_ioctl(struct file *filp,
case KVM_SET_CLOCK: {
struct kvm_clock_data user_ns;
u64 now_ns;
- s64 delta;
r = -EFAULT;
if (copy_from_user(&user_ns, argp, sizeof(user_ns)))
@@ -4060,10 +4087,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = 0;
local_irq_disable();
- now_ns = get_kernel_ns();
- delta = user_ns.clock - now_ns;
+ now_ns = __get_kvmclock_ns(kvm);
+ kvm->arch.kvmclock_offset += user_ns.clock - now_ns;
local_irq_enable();
- kvm->arch.kvmclock_offset = delta;
kvm_gen_update_masterclock(kvm);
break;
}
@@ -4071,10 +4097,8 @@ long kvm_arch_vm_ioctl(struct file *filp,
struct kvm_clock_data user_ns;
u64 now_ns;
- local_irq_disable();
- now_ns = get_kernel_ns();
- user_ns.clock = kvm->arch.kvmclock_offset + now_ns;
- local_irq_enable();
+ now_ns = get_kvmclock_ns(kvm);
+ user_ns.clock = now_ns;
user_ns.flags = 0;
memset(&user_ns.pad, 0, sizeof(user_ns.pad));
@@ -7539,7 +7563,7 @@ int kvm_arch_hardware_enable(void)
* before any KVM threads can be running. Unfortunately, we can't
* bring the TSCs fully up to date with real time, as we aren't yet far
* enough into CPU bringup that we know how much real time has actually
- * elapsed; our helper function, get_kernel_ns() will be using boot
+ * elapsed; our helper function, ktime_get_boot_ns() will be using boot
* variables that haven't been updated yet.
*
* So we simply find the maximum observed TSC above, then record the
@@ -7774,7 +7798,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
mutex_init(&kvm->arch.apic_map_lock);
spin_lock_init(&kvm->arch.pvclock_gtod_sync_lock);
- kvm->arch.kvmclock_offset = -get_kernel_ns();
+ kvm->arch.kvmclock_offset = -ktime_get_boot_ns();
pvclock_update_vm_gtod_copy(kvm);
INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index a82ca466b62e..e8ff3e4ce38a 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -148,11 +148,6 @@ static inline void kvm_register_writel(struct kvm_vcpu *vcpu,
return kvm_register_write(vcpu, reg, val);
}
-static inline u64 get_kernel_ns(void)
-{
- return ktime_get_boot_ns();
-}
-
static inline bool kvm_check_has_quirk(struct kvm *kvm, u64 quirk)
{
return !(kvm->arch.disabled_quirks & quirk);
@@ -164,6 +159,7 @@ void kvm_set_pending_timer(struct kvm_vcpu *vcpu);
int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr);
+u64 get_kvmclock_ns(struct kvm *kvm);
int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
gva_t addr, void *val, unsigned int bytes,
--
1.8.3.1
--
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