[Devel] [PATCH RHEL7 COMMIT] ms/KVM: x86: introduce get_kvmclock_ns
Konstantin Khorenko
khorenko at virtuozzo.com
Mon Oct 24 05:07:10 PDT 2016
The commit is pushed to "branch-rh7-3.10.0-327.36.1.vz7.19.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.36.1.vz7.19.3
------>
commit 5bac74955a0646b4ffd676c6e09b23e7d3c1d318
Author: Paolo Bonzini <pbonzini at redhat.com>
Date: Mon Oct 24 16:07:10 2016 +0400
ms/KVM: x86: introduce get_kvmclock_ns
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 at redhat.com>
(cherry picked from commit 108b249c453dd7132599ab6dc7e435a7036c193f)
some code adapted to virtuozzo's branch
Signed-off-by: Denis Plotnikov <dplotnikov at virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan at virtuozzo.com>
Signed-off-by: "Denis V. Lunev" <den at openvz.org>
---
arch/x86/include/asm/pvclock.h | 8 ++++----
arch/x86/kernel/pvclock.c | 6 ++++--
arch/x86/kvm/hyperv.c | 2 +-
arch/x86/kvm/x86.c | 45 ++++++++++++++++++++++++++++++++----------
arch/x86/kvm/x86.h | 1 +
arch/x86/vdso/vclock_gettime.c | 3 ++-
6 files changed, 47 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 628954c..7ec049a 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -60,16 +60,16 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
}
static __always_inline
-u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src)
+u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src, u64 tsc)
{
- u64 delta = __native_read_tsc() - src->tsc_timestamp;
+ u64 delta = tsc - src->tsc_timestamp;
return pvclock_scale_delta(delta, src->tsc_to_system_mul,
src->tsc_shift);
}
static __always_inline
unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
- cycle_t *cycles, u8 *flags)
+ cycle_t *cycles, u8 *flags, u64 tsc)
{
unsigned version;
cycle_t ret, offset;
@@ -83,7 +83,7 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
* below, resulting in violation of monotonicity.
*/
rdtsc_barrier();
- offset = pvclock_get_nsec_offset(src);
+ offset = pvclock_get_nsec_offset(src, tsc);
ret = src->system_time + offset;
ret_flags = src->flags;
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 2f355d2..07391d4 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -65,7 +65,8 @@ u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
u8 flags;
do {
- version = __pvclock_read_cycles(src, &ret, &flags);
+ version = __pvclock_read_cycles(src, &ret, &flags,
+ native_read_tsc());
} while ((src->version & 1) || version != src->version);
return flags & valid_flags;
@@ -79,7 +80,8 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
u8 flags;
do {
- version = __pvclock_read_cycles(src, &ret, &flags);
+ version = __pvclock_read_cycles(src, &ret, &flags,
+ native_read_tsc());
} while ((src->version & 1) || version != src->version);
if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 9d60d33..0f07375 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 31b59bf..d39e4b5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1595,6 +1595,35 @@ 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;
+ u64 ns;
+ u8 flags;
+
+ if (vcpu->arch.hv_clock.flags & PVCLOCK_TSC_STABLE_BIT) {
+ u64 tsc = kvm_x86_ops->read_l1_tsc(vcpu, native_read_tsc());
+ __pvclock_read_cycles(&vcpu->arch.hv_clock, &ns, &flags, tsc);
+ } else {
+ ns = ktime_to_ns(ktime_get_boottime()) + 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;
@@ -3943,7 +3972,6 @@ 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)))
@@ -3955,10 +3983,9 @@ 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;
}
@@ -3966,10 +3993,8 @@ 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));
@@ -7375,7 +7400,7 @@ 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
@@ -7579,7 +7604,7 @@ 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_to_ns(ktime_get_boottime());
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 61eda944..ab4c57a 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -159,6 +159,7 @@ void kvm_after_handle_nmi(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,
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 3d16e23..9468944 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -107,7 +107,8 @@ static notrace cycle_t vread_pvclock(int *mode)
pvti = get_pvti(cpu);
- version = __pvclock_read_cycles(&pvti->pvti, &ret, &flags);
+ version = __pvclock_read_cycles(&pvti->pvti, &ret, &flags,
+ __native_read_tsc());
/*
* Test we're still on the cpu as well as the version.
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