linux-kernel - [PATCH 0/2] Automatically grab wallclock time updates from hypervisor

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Message-Id: <1251805848-17451-1-git-send-email-glommer@redhat.com>
Date:	Tue,  1 Sep 2009 07:50:46 -0400
From:	Glauber Costa <glommer@...hat.com>
To:	kvm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, avi@...hat.com
Subject: [PATCH 0/2] Automatically grab wallclock time updates from hypervisor

Hi folks,

In this proposed patch, I am introducing a worker fired by kvmclock that updates
guest wallclock periodically to reflect changes in the host's wallclock. With this
patch, a large pool of VMs will no longer have to run NTP in all of its guests.

The worker does that at a configurable interval, with a minimum granularity of 1
second. So, although not exactly cheap, the msr write needed to get an updated
wallclock value won't pose a heavy burden on the system.

It is also possible to disable it completely if this behaviour is undesired for
a specific scenario.

diffstat follows:

 arch/x86/include/asm/kvm_para.h |    6 +++
 arch/x86/kernel/kvmclock.c      |   77 ++++++++++++++++++++++++++++++++++-----
 kernel/sysctl.c                 |   13 +++++++
 3 files changed, 87 insertions(+), 9 deletions(-)

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