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author | Paolo Bonzini <pbonzini@redhat.com> | 2016-09-01 12:21:03 (GMT) |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-09-20 07:26:15 (GMT) |
commit | 108b249c453dd7132599ab6dc7e435a7036c193f (patch) | |
tree | eb600c0558d7032bc1b0c62066f74ac109bd4fd7 /arch/x86/include | |
parent | 67198ac3f37ffb150f1c95fae16b597339eabc9d (diff) | |
download | linux-108b249c453dd7132599ab6dc7e435a7036c193f.tar.xz |
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.
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/include')
-rw-r--r-- | arch/x86/include/asm/pvclock.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h index d019f0c..3ad741b 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; |