Re: [PATCH v4 00/10] make L2's kvm-clock stable, get rid of pvclock_gtod_copy in KVM

Paolo Bonzini
2017-08-02T16:10:00Z

On 02/08/2017 16:38, Denis Plotnikov wrote:
> V4:
> * removed "is stable" function with vague definition of stability
> there is the only function which does time with cycle stamp getting
> * some variables renamed
> * some patches split into smaller once
> * atomic64_t usage is replaced with atomic_t

Thanks. This looks good from the KVM point of view. Let's see what the
timekeeping guys think.

Paolo

> V3:
> Changing the timekeeper interface for clocksource reading looks like
> an overkill to achive the goal of getting cycles stamp for KVM.
> Instead extend the timekeeping interface and add functions which provide
> necessary data: read clocksource with cycles stamp, check whether the
> clock source is stable.
>
> Use those functions and improve existing timekeeper functionality to
> replace pvclock_gtod_copy scheme in masterclock data calculation.
>
> V2:
> The main goal is to make L2 kvm-clock be stable when it's running over L1
> with stable kvm-clock.
>
> The patch series is for x86 architecture only. If the series is approved
> I'll do changes for other architectures but I don't have an ability to
> compile and check for every single on (help needed)
>
> The patch series do the following:
>
> * change timekeeper interface to get cycles stamp value from
> the timekeeper
> * get rid of pvclock copy in KVM by using the changed timekeeper
> interface: get time and cycles right from the timekeeper
> * make KVM recognize a stable kvm-clock as stable clocksource
> and use the KVM masterclock in this case, which means making
> L2 stable when running over stable L1 kvm-clock
>
> Denis Plotnikov (10):
> timekeeper: introduce extended clocksource reading callback
> timekeeper: introduce boot field in system_time_snapshot
> timekeeper: use the extended reading function on snapshot acquiring
> tsc: implement the extended tsc reading function
> KVM: x86: switch to masterclock update using timekeeper functionality
> timekeeper: add clocksource change notifier
> KVM: x86: remove not used pvclock_gtod_copy
> pvclock: add parameters to store stamp data in pvclock reading
> function
> pvclock: add clocksource change notification on changing of tsc stable
> bit
> kvmclock: implement the extended reading function
>
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/include/asm/pvclock.h | 3 +-
> arch/x86/kernel/kvmclock.c | 19 +++-
> arch/x86/kernel/pvclock.c | 37 +++++-
> arch/x86/kernel/tsc.c | 10 ++
> arch/x86/kvm/trace.h | 31 ++---
> arch/x86/kvm/x86.c | 242 ++++++++--------------------------------
> arch/x86/xen/time.c | 2 +-
> include/linux/clocksource.h | 11 +-
> include/linux/cs_notifier.h | 17 +++
> include/linux/timekeeping.h | 5 +
> kernel/time/timekeeping.c | 68 ++++++++++-
> 12 files changed, 219 insertions(+), 228 deletions(-)
> create mode 100644 include/linux/cs_notifier.h
>