From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: Re: [PATCH][v4] PV extension of HVM(hybrid) support
	in Xen
Date: Mon, 01 Mar 2010 20:39:34 -0800
Message-ID: <4B8C9686.40608@goop.org>
References: <201003011743.41341.sheng@linux.intel.com>
	<201003011940.50685.sheng@linux.intel.com>
	<4B8C6EC3.2020307@goop.org>
	<201003021136.02590.sheng@linux.intel.com>
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To: Sheng Yang <sheng@linux.intel.com>
Cc: Ian Campbell <Ian.Campbell@eu.citrix.com>, Ian Pratt <Ian.Pratt@eu.citrix.com>, xen-devel <xen-devel@lists.xensource.com>, Tim Deegan <Tim.Deegan@citrix.com>, Keir Fraser <Keir.Fraser@eu.citrix.com>
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On 03/01/2010 07:36 PM, Sheng Yang wrote:
>> static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
>> {
>>         u64 delta = native_read_tsc() - shadow->tsc_timestamp;
>>         return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow-
>> tsc_shift);
>> }
>>      
> tsc_timestamp take the vcpu beginning at 0, so that's the assumption.

Why would it be 0?  Xen sets tsc_timestamp to the current tsc when it 
updates the time parameters, which is whenever the vcpu is scheduled on 
a pcpu (and other times).  There's no expectation that the tsc starts 
from 0, since that won't ever be the case.

     J