[RFC PATCH 0/2] make L2 kvm-clock stable

[Denis Plotnikov <dplotnikov@virtuozzo.com>]

The goal of the series is to make L2's kvm-clock guest stable when possible.

It's possible when the L2 is running over L1 with a stable paravirtualized
clocksource.

To acomplish the goal I can see two approaches:

1. Use currently existing in KVM "monotonic timekeeper shadow".

   This approach repeats functionality of time calculation from the kerenl
   monotonic timekeeper. To acomplish the goal it's needed to add time
   calculation functions for paravirtualized clocksources to KVM which
   implies repeating the functionality from the timekeeper.
   It seems to me that this approach is not the best one because of code 
   repetition, data shadowing, keeping logic consistent with timekeeper's one.
   I would consider using the next approach.

2. Use existing timekeeper functionality with extended interface

   This approach deligates all time related calculations to the kernel
   timekeeper instead of having timekeeper shadow and time calculating logic
   in KVM.
   Using this approach will allow to remove the monotonic timekeeping shadow,
   but ask to change timekeeper interface in a way that will add an ability
   to return the timestamp value used for time calculations (if any) because this 
   value is needed in KVM (and possibly somewhere else in the future).

This patch series implements the 2nd approach (for now, for x86 only).
Could you please give me some feedback about it?

Denis Plotnikov (2):
  timekeeper: change interface of clocksource reding functions
  KVM: x86: add support of kvm-clock stablity in L2

 arch/x86/hyperv/hv_init.c           |   4 +-
 arch/x86/include/asm/kvm_host.h     |   2 +-
 arch/x86/include/asm/pvclock.h      |   2 +-
 arch/x86/kernel/hpet.c              |   4 +-
 arch/x86/kernel/kvmclock.c          |  19 ++-
 arch/x86/kernel/pvclock.c           |  11 +-
 arch/x86/kernel/tsc.c               |   7 +-
 arch/x86/kvm/x86.c                  | 294 ++++++++++--------------------------
 arch/x86/lguest/boot.c              |   2 +-
 arch/x86/platform/uv/uv_time.c      |  10 +-
 arch/x86/xen/time.c                 |  21 ++-
 arch/x86/xen/xen-ops.h              |   2 +-
 drivers/clocksource/acpi_pm.c       |  12 +-
 drivers/hv/hv_util.c                |   6 +-
 include/linux/clocksource.h         |   9 +-
 include/linux/timekeeper_internal.h |   2 +-
 include/linux/timekeeping.h         |  34 ++++-
 kernel/time/clocksource.c           |   4 +-
 kernel/time/jiffies.c               |   2 +-
 kernel/time/timekeeping.c           |  66 +++++---
 20 files changed, 221 insertions(+), 292 deletions(-)

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2.7.4