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Re: [Xen-devel] [PATCH 2/3] timekeeping: sync persistent clock and RTC on system time step changes

On 05/28/2013 01:25 PM, Konrad Rzeszutek Wilk wrote:
On Tue, May 28, 2013 at 01:11:33PM -0700, John Stultz wrote:
On 05/28/2013 01:03 PM, John Stultz wrote:
On 05/28/2013 12:48 PM, Konrad Rzeszutek Wilk wrote:
On Tue, May 28, 2013 at 12:09:14PM -0700, John Stultz wrote:
On 05/28/2013 11:31 AM, Konrad Rzeszutek Wilk wrote:
On Tue, May 28, 2013 at 07:26:14PM +0100, David Vrabel wrote:
On 15/05/13 19:10, John Stultz wrote:
Ok, so really, as soon as the Dom0 time is set by NTP,
all guests will
see the right time? That makes more sense, and means the window for
these sorts of issues is reasonably quite small.
It's a small window but it's occurring in our automated test system.

David: So I'm less inclined to merge this individual
change, but if you
still feel strongly about it, let me know and we can
circle around on it
after you've addressed the specific issues I pointed out earlier.
This patch was the actual bug fix but I've reworked it to use the
pvclock_gtod notifier chain as this seemed to be what KVM hosts were
using to maintain a clock for guests.  Please review the
new series, thanks.
Looks good.

John if you are OK I am thinking to push this to Linus
shortly as it is
fixing a bug.
I'm really not sure I'd call this a bug.  That seems like an
over-reaction to a misconfigured system.

Or if there is a bug, I'm not sure its been clearly explained.
The #1 patch - b/c you try to set the RTC time and it actually
never takes. Meaning
on the next time the machine is booted the time is again off.
Ok. Yea, that one I'm fine with and have queued for 3.11.

If you want to push it as a bug fix for 3.10, I'll leave it to you
to push to Linus.
Probably obvious, but just in case its not clear:

Though if that one patch goes to linus for 3.10, it needs to be
reworked to not depend on the mach_set_rtc_mmss() interface change
it currently depends on. The interface change is not bugfix
You are referring to commit 3195ef59cb42cda3aeeb24a7fd2ba1b900c4a3cc
Author: Prarit Bhargava <prarit@xxxxxxxxxx>
Date:   Thu Feb 14 12:02:54 2013 -0500

     x86: Do full rtc synchronization with ntp

No. I mean David's patch:
    x86: Increase precision of x86_platform.get/set_wallclock()

That one should be held back for 3.11.

But the calling of mach_set_rtc_mmss() from the Xen set_wallclock hook would still be reasonable to go in 3.10 (limited impact to only Xen, fixing a bug), but it would have to limit the call to the second granular mach_set_rtc_mmss() in 3.10.


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