KVM: x86: introduce get_kvmclock_ns

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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>

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This commit is contained in:

Paolo Bonzini 2016-09-01 14:21:03 +02:00

parent 67198ac3f3

commit 108b249c45

6 changed files with 43 additions and 22 deletions

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2

arch/x86/entry/vdso/vclock_gettime.c

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arch/x86/include/asm/pvclock.h

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arch/x86/kernel/pvclock.c

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arch/x86/kvm/hyperv.c

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arch/x86/kvm/x86.c

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arch/x86/kvm/x86.h

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