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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>, "Winston L Wang" <winston.l.wang@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Fri, 15 Apr 2011 08:06:35 +0100
Cc: Jinsong Liu <jinsong.liu@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, KeirFraser <keir@xxxxxxx>, Yunhong Jiang <yunhong.jiang@xxxxxxxxx>, Donald D Dugger <donald.d.dugger@xxxxxxxxx>, Xin Li <xin.li@xxxxxxxxx>
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>>> On 14.04.11 at 23:06, Keir Fraser <keir.xen@xxxxxxxxx> wrote:
> On 14/04/2011 19:33, "Wang, Winston L" <winston.l.wang@xxxxxxxxx> wrote:
>> 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.

So do I think - I already tried to carefully pick the place where this
is best done.


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