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RE: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs u

To: Keir Fraser <keir.xen@xxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits
From: "Wang, Winston L" <winston.l.wang@xxxxxxxxx>
Date: Thu, 14 Apr 2011 14:37:19 -0700
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Cc: "Liu, Jinsong" <jinsong.liu@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, KeirFraser <keir@xxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>, "Dugger, Donald D" <donald.d.dugger@xxxxxxxxx>, "Li, Xin" <xin.li@xxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits
> -----Original Message-----
> From: Keir Fraser [mailto:keir.xen@xxxxxxxxx]
> Sent: Thursday, April 14, 2011 2:06 PM
> On 14/04/2011 19:33, "Wang, Winston L" <winston.l.wang@xxxxxxxxx> wrote:
> > Jan and Keir,
> >
> > Great efforts for turning the test code re-validate the processor
> with
> > (X86_FEATURE_TSC_RELIABLE) set. We know for sure that the broken old
> > processors any write TSC will Zero the upper 32 bit. So can we move
> this test
> > code as early as possible, say immediately after the early Processor
> init code
> > where checking CPU id and set X86_FEATURE_TSC_RELIABLE?
> For our meaning of TSC_RELIABLE, there's no need for its setting to
> rely on
> TSC 64-bit writability. I think leaving it where it is in
> init_xen_time() is probably fine.

It's fine with me.


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