From: Dan Magenheimer <dan.magenheimer@oracle.com>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: "Xu, Dongxiao" <dongxiao.xu@intel.com>,
xen-devel@lists.xensource.com,
Keir Fraser <Keir.Fraser@eu.citrix.com>,
"Zhang, Xiantao" <xiantao.zhang@intel.com>
Subject: RE: tsc_mode == 1 and hvm guests
Date: Mon, 10 May 2010 08:30:03 -0700 (PDT) [thread overview]
Message-ID: <bc6cb662-95fd-4fc6-abec-5b85e235865f@default> (raw)
In-Reply-To: <alpine.DEB.2.00.1005101612140.11380@kaball-desktop>
> However I can tell you that without the patch when vtsc == 1
> hvm_gtsc_need_scale returns 0 therefore scaling is never done.
> For this reason I cannot see how the tsc frequency would remain the
> same when vtsc == 1 and the underling hardware has a different tsc
> rate.
> The offset would be OK though.
I think when vtsc==1 (e.g. tsc_mode==1), no scaling is
done on HVM as the underlying machine is presented
to be a 1GHz machine (regardless of the true TSC rate
or whether migration had occurred or not). PV also
presented only a 1GHz clock for awhile and I changed
it (with input from Jeremy as I recall) so that it
would be less confusing to end users who might be
confused by seeing Linux boot output claiming the
underlying machine "is only running at 1GHz!!".
There's a large number of different combinations to be
tested (and possibly broken) here. I'd prefer to see
"I tested this feature on 4.0.0 and it doesn't work" before
putting a patch into the stable stream. For xen-unstable
I have no problem with the patch of course.
next prev parent reply other threads:[~2010-05-10 15:30 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-06 11:41 tsc_mode == 1 and hvm guests Stefano Stabellini
2010-05-06 12:04 ` Keir Fraser
2010-05-06 15:03 ` Dan Magenheimer
2010-05-07 8:18 ` Zhang, Xiantao
2010-05-07 19:06 ` Stefano Stabellini
2010-05-07 19:35 ` Dan Magenheimer
2010-05-10 12:41 ` Stefano Stabellini
2010-05-10 12:42 ` Keir Fraser
2010-05-10 12:58 ` Stefano Stabellini
2010-05-10 14:47 ` Dan Magenheimer
2010-05-10 14:55 ` Stefano Stabellini
2010-05-10 15:01 ` Dan Magenheimer
2010-05-10 15:19 ` Stefano Stabellini
2010-05-10 15:30 ` Dan Magenheimer [this message]
2010-05-10 16:36 ` Stefano Stabellini
2010-05-09 14:04 ` Zhang, Xiantao
2010-05-10 12:48 ` Stefano Stabellini
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