[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCHv5 0/4] xen: maintain an accurate persistent clock in more cases

On 06/20/2013 12:16 PM, David Vrabel wrote:
Xen guests use the Xen wallclock as their persistent clock.  This is a
software only clock in the hypervisor that is used by guests instead
of a real hardware RTC.

The kernel has limited support for updating the persistent clock or
RTC when NTP is synced.  This has the following limitations:

* The persistent clock is not updated on step changes.  This leaves a
   window where it will be incorrect (while NTP resyncs).

* Xen guests use the Xen wallclock as their persistent clock.  dom0
   maintains this clock so it is persistent for domUs but not dom0

These limitations mean that guests started before NTP is synchronized
will start with an incorrect wallclock time and the hardware RTC will
not be updated (as on bare metal).

These series fixes the above limitations and depends on "x86: increase
precision of x86_platform.get/set_wallclock()" which was previously

Changes since v4:

Dropped the change to disable non-boot CPUs during suspend on Xen as
migration downtime was too poor.  Instead, provide
hrtimers_late_resume() for use by Xen's resume code to replace the
call of clock_was_set().  Fix two unused variable warnings.

Ok, I've got these 4 in my pending stack. As long as Thomas doesn't object to the first two, and it doesn't run into any trouble in testing, I'll send them along for 3.12. (Acks from Xen maintainers would be nice for the last two as well).

Thanks for all the effort through all the revisions here!


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.