From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Glauber Costa <glommer@gmail.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>, Avi Kivity <avi@qumranet.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
kvm-devel <kvm-devel@lists.sourceforge.net>
Subject: Re: Use of barriers in pvclock ABI
Date: Mon, 11 Aug 2008 09:02:15 -0700 [thread overview]
Message-ID: <48A06287.8020906@goop.org> (raw)
In-Reply-To: <5d6222a80808110718i6a600858v7bdb5e08054ebefa@mail.gmail.com>
Glauber Costa wrote:
> Okay for guest vcpu, but what about physical cpus?
>
> IIRC, the checks are there, and so strict, to account for the
> possiblity of the vcpu to be migrated to another cpu in the middle of
> the
> clock reading.
>
That's fine. As part of rescheduling a vcpu on a new pcpu, the clock
record will be updated with the new cpu's parameters, but that update
will be complete by the time the vcpu gets rescheduled. The version
check and loop still needs to be there, but it will never see an
inconsistent (partially updated) clock record.
J
prev parent reply other threads:[~2008-08-11 16:02 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-08 19:51 Use of barriers in pvclock ABI Jeremy Fitzhardinge
2008-08-11 7:08 ` Gerd Hoffmann
2008-08-11 14:15 ` Avi Kivity
2008-08-11 14:18 ` Glauber Costa
2008-08-11 14:35 ` Avi Kivity
2008-08-11 14:49 ` Gerd Hoffmann
2008-08-11 16:02 ` Jeremy Fitzhardinge [this message]
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