From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.xen@gmail.com>
Subject: Re: [Xen-users]   Re: Xen 4 TSC problems
Date: Thu, 18 Oct 2012 08:55:04 +0100
Message-ID: <CCA57468.41EF3%keir.xen@gmail.com>
References: <1350546021.28188.20.camel@dagon.hellion.org.uk>
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To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, Dan Magenheimer <dan.magenheimer@oracle.com>, Mauro <mrsanna1@gmail.com>, Olivier Hanesse <olivier.hanesse@gmail.com>, Jan Beulich <JBeulich@suse.com>, Xen Users <xen-users@lists.xensource.com>, Mark Adams <mark@campbell-lange.net>
List-Id: xen-devel@lists.xenproject.org

On 18/10/2012 08:40, "Ian Campbell" <Ian.Campbell@citrix.com> wrote:

> On Wed, 2012-10-17 at 17:15 +0100, Keir Fraser wrote:
>> @@ -540,6 +541,14 @@ static void plt_overflow(void *unused)
>>          plt_wrap = __read_platform_stime(plt_stamp64 + plt_mask + 1);
>>          if ( ABS(plt_wrap - now) > ABS(plt_now - now) )
>>              break;
>> +        rdtscll(tsc);
>> +        printk("XXX plt_overflow: plt_now=%"PRIx64" plt_wrap=%"PRIx64
>> +               " now=%"PRIx64" old_stamp=%"PRIx64" new_stamp=%"PRIx64
>> +               " plt_stamp64=%"PRIx64" plt_mask=%"PRIx64
>> +               " tsc=%"PRIx64" tsc_stamp=%"PRIx64"\n",
>> +               plt_now, plt_wrap, now, old_stamp, plt_stamp, plt_stamp64,
>> +               plt_mask, tsc, this_cpu(cpu_time).local_tsc_stamp);
>> +        break;
> 
> Is the break here, making the following update to plt_stamp64 dead code
> deliberate?

Yes, it's a hack to disable the timer-has-apparently-wrapped workaround.

 -- Keir

>>          plt_stamp64 += plt_mask + 1;
>>      }
>>      if ( i != 0 )
> 
> Ian.
> 
>