From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.xen@gmail.com>
Subject: Re: [PATCH] x86/time: fix scale_delta() inline assembly
Date: Mon, 26 Nov 2012 19:23:28 +0000
Message-ID: <CCD97230.460F4%keir.xen@gmail.com>
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To: Dan Magenheimer <dan.magenheimer@oracle.com>, Sylvain Munaut <s.munaut@whatever-company.com>
Cc: Jan Beulich <JBeulich@suse.com>, xen-devel <xen-devel@lists.xen.org>
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On 26/11/2012 17:12, "Dan Magenheimer" <dan.magenheimer@oracle.com> wrote:

>> From: Sylvain Munaut [mailto:s.munaut@whatever-company.com]
>> Subject: Re: [Xen-devel] [PATCH] x86/time: fix scale_delta() inline assembly
>> 
>> I've just deployed this to a couple test servers that exhibited the problem.
>> 
>> What I don't really understand is why are some HW affected and not others ?
> 
> I don't know, but I'd imagine there is something in the x86 platform
> software (aka firmware) of those machines that runs and blocks execution
> of Xen for long enough (via NMI/MCE/SMI) for the platform timer to
> overflow, and this doesn't occur on other machines.

It is just luck of the draw. There is no actual platform timer overflow
happening when this bug triggers.

 -- Keir

> Maybe Jan has a better idea...