Re: [Xen-devel] [PATCH 0/3] xen: fix various wallclock problems

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 15/10/12 10:26, Ian Campbell wrote:
> On Fri, 2012-10-12 at 17:25 +0100, David Vrabel wrote:
>> On 12/10/12 13:57, David Vrabel wrote:
>>> This series (with some toolstack updates) corrects a number of cases
>>> where a guest can see an incorrect wallclock time.
>>>
>>> 1. Systems with NTP won't periodically synchronize the hardware RTC so
>>> the wallclock may be incorrect after a reboot.
>>>
>>> 2. The wallclock is always ~500 ms behind the correct time.
>>>
>>> 3. If the system time was stepped and NTP isn't synchronized yet, the
>>> wallclock will still have the incorrect time.  The fix for this
>>> requires the toolstack to synchronize the wallclock -- patch #3
>>> provides the mechanism for this.
>>
>> These tables should help.
>>
>> Before:
>>
>>               |                Updates
>> Process            | System Time?  Xen Wallclock?  Hardware Clock?
>> -------------------------------------------------------------
>> date -s       | X
>> hwclock -w    |                               X
>> ntpd          | X             X[*]
>> ntpdate       | X
> 
> What does the equivalent table for native look like?
> 
> Is the "updated hardware clock" column in that caseis union of xen
> wallclock and hardware clock columns here?

Yes.

              |         Updates
Process       | System Time?  Hardware Clock?
---------------------------------------------
date -s       | X
hwclock -w    |               X
ntpd          | X             X[*]
ntpdate       | X

David

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