[Xen-devel] Re: [PATCH] x86/pvclock-xen: zero last_value on resume

[Glauber Costa <glommer@xxxxxxxxxx>]

On Tue, 2010-10-26 at 09:59 -0700, Jeremy Fitzhardinge wrote:
> 
> If the guest domain has been suspend/resumed or migrated, then the
> system clock backing the pvclock clocksource may revert to a smaller
> value (ie, can be non-monotonic across the migration/save-restore).
> Make sure we zero last_value in that case so that the domain
> continues to see clock updates.
> 
> [ I don't know if kvm needs an analogous fix or not. ]
After migration, save/restore, etc, we issue an ioctl where we tell
the host the last clock value. That (in theory) guarantees monotonicity.

I am not opposed to this patch in any way, however.



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