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Re: [Xen-devel] Re: system freeze when processor.ko is loaded during boo

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Martin Wilck <mwilck@xxxxxxxx>, Haitao Shan <maillists.shan@xxxxxxxxx>
Subject: Re: [Xen-devel] Re: system freeze when processor.ko is loaded during boot
From: Keir Fraser <keir@xxxxxxx>
Date: Tue, 12 Apr 2011 14:59:46 +0100
Cc: "Liu, Jinsong" <jinsong.liu@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Yunhong Jiang <yunhong.jiang@xxxxxxxxx>, Donald D Dugger <donald.d.dugger@xxxxxxxxx>, Xin Li <xin.li@xxxxxxxxx>, Gang Wei <gang.wei@xxxxxxxxx>
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Thread-topic: [Xen-devel] Re: system freeze when processor.ko is loaded during boot
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On 04/04/2011 10:22, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

> Haitao, while it is quite clear that with the current
> implementation we just can't use C states above C1 on CPUs
> that may halt the TSC in C2 or C3 *and* that don't allow
> writing the full TSC, this family/model based determination
> clearly isn't nice (and since it is a white list, it can't possibly be
> complete). An alternative would seem to be to probe for how
> TSC writes behave (thus at once covering eventual other
> vendors' CPUs that may have similar shortcomings). That of
> course would need to be done early, so that resetting the
> upper bits to zero wouldn't have any adverse effect. What
> do you think?

We should do early run-time test of this from the BSP then, on failure,
avoid all further potential uses of write_tsc() in an appropriate way (e.g.,
bail early in cstate_restore_tsc(), synchronize_tsc_*(), and avoid use of

 -- Keir

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