Suleiman Souhlal <sulei...@google.com> writes: > When CONFIG_KVMCLOCK_HOST_TIMEKEEPING is enabled, and the host > supports it, update our timekeeping parameters to be the same as > the host. This lets us have our time synchronized with the host's, > even in the presence of host NTP or suspend. > > When enabled, kvmclock uses raw tsc instead of pvclock. > > When enabled, syscalls that can change time, such as settimeofday(2) > or adj_timex(2) are disabled in the guest. > > Signed-off-by: Suleiman Souhlal <sulei...@google.com> > --- > arch/x86/Kconfig | 9 +++ > arch/x86/include/asm/kvmclock.h | 2 + > arch/x86/kernel/kvmclock.c | 127 +++++++++++++++++++++++++++++++- > kernel/time/timekeeping.c | 21 ++++++ > 4 files changed, 155 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 4195f44c6a09..37299377d9d7 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -837,6 +837,15 @@ config PARAVIRT_TIME_ACCOUNTING > config PARAVIRT_CLOCK > bool > > +config KVMCLOCK_HOST_TIMEKEEPING > + bool "kvmclock uses host timekeeping" > + depends on KVM_GUEST > + ---help--- > + Select this option to make the guest use the same timekeeping > + parameters as the host. This means that time will be almost > + exactly the same between the two. Only works if the host uses "tsc" > + clocksource. > +
I'd also like to speak up against this config, it is confusing. In case the goal is to come up with a TSC-based clock for guests which will return the same as clock_gettime() on the host (or, is the goal to just have the same reading for all guests on the host?) I'd suggest we create a separate (from KVMCLOCK) clocksource (mirroring host timekeeper) and guests will be free to pick the one they like. -- Vitaly
