linux-kernel - [PATCH v5 0/6] KVM: x86: get rid of pvclock_gtod

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Message-Id: <1504106628-172372-1-git-send-email-dplotnikov@virtuozzo.com>
Date:   Wed, 30 Aug 2017 18:23:42 +0300
From:   Denis Plotnikov <dplotnikov@...tuozzo.com>
To:     pbonzini@...hat.com, rkrcmar@...hat.com, kvm@...r.kernel.org,
        john.stultz@...aro.org, tglx@...utronix.de
Cc:     mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
        x86@...nel.org, rkagan@...tuozzo.com, den@...tuozzo.com
Subject: [PATCH v5 0/6] KVM: x86: get rid of pvclock_gtod_copy

V5:
  It was decided to split the series
  "make L2's kvm-clock stable, get rid of pvclock_gtod_copy in KVM"
  into two parts to make the changes finer grained:
    1. get rid of pvclock_gtod_copy in KVM 
    2. make L2's kvm-clock stable
  This V5 series implements the 1st part. This part gets rid
  of pvclock_gtod_copy by switching to use the timekeeper functionality
  being extended. This new scheme doesn't add any new notifiers and keeps
  using the existing one (see patch 6 description) which had been used by
  the pvclock_gtod_copy to keep track timekeeper data changes.

  The 2nd part is being discussed and is going to be sent later on.

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
 
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 (6):
  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
  KVM: x86: remove not used pvclock_gtod_copy

 arch/x86/include/asm/kvm_host.h |   2 +-
 arch/x86/kernel/tsc.c           |  10 ++
 arch/x86/kvm/trace.h            |  31 ++---
 arch/x86/kvm/x86.c              | 245 +++++++++-------------------------------
 include/linux/clocksource.h     |  11 +-
 include/linux/timekeeping.h     |   5 +
 kernel/time/timekeeping.c       |  17 ++-
 7 files changed, 104 insertions(+), 217 deletions(-)

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2.7.4